UI Extension Master Gardeners UI Extension Events UI Extension Idaho Landscapes and Gardens Seasonal Topics UI Extension Idaho Landscapes and Gardens Get Answers UI Extension Idaho Landscapes and Gardens UI Extension Idaho's Growing Regions University of Idaho Extension UI Extension Idaho Landscapes and Gardens UI Extension Idaho Landscapes and Gardens Image Map
Aug 162012
 

ZinnaAnnual flowers and foliage plants provide many options for short-term accent and beautification in a landscape. By definition, annuals are those plants that live and bloom for only one year. They die at the end of the growing season and must be replanted or reseed themselves the following season.

In some cases, desirable landscape plants such as impatiens, coleus, and geraniums are actually tender perennials, meaning they live for many years in warm climates, but cannot survive our Idaho winters. We refer to and treat these plants as annuals in the garden.

The effort and expense of replacing plants each year are one drawback to using annuals in the garden. However, annuals are unmatched in variety, color, bloom period, and adaptability. Many can be grown from seed for pennies a plant, There is an annual plant for every situation in the landscape and all these factors compensates for the extra effort involved in establishment, removal and replanting. Some annuals, such as cosmos, re-seed freely, establishing themselves in a garden year after year.

Annual flowers can be used in traditional beds, rock gardens, cutting gardens, borders, window boxes, containers, and hanging baskets. They add interest and color to architectural features. They can also be used to beautify uninteresting areas in our landscapes or used as screens to hide undesirable features. Some annuals, like California poppy and sunflower grow in dry, rocky, shallow areas where little else will grow and bloom.

Your local garden center will likely stock thousands of different annuals for the garden and containers, and exciting new cultivars are being released continually.

In this section you’ll find a complete guide to selecting, planting, and caring for annual flowers and foliage plants. Use the links on the left to navigate through a wealth of information.

 August 16, 2012
Aug 162012
 

Selection of the proper plant species and cultivars determine your ultimate success with annuals. Care must be taken to choose plants that complement their surroundings, are adapted to the local climate and situation, and provide the intended effect.

DianthusAnnuals can be categorized based on growth characteristics or intended use, making selection easier. Useful groupings include hardiness, drought and heat tolerance, shade tolerance, fragrance, exhibition of ornamental foliage, ability to vine or climb, utility for hanging baskets, or use for cut flowers.

Additional outstanding information designed to provide assistance with selection of annual flowers is available from a number of sources. These include:

There are several internet sites with excellent pictures of annual flowers. Here are some of the best.

 August 16, 2012
Aug 162012
 
Hardy Annuals

These plants tolerate frost and cool growing conditions.  Many bloom in early spring or can be planted in late fall to add color to the landscape.  Hardy annuals are irreplaceable for those who live in the cool, high-elevation areas of Idaho, but can be good additions to the spring and fall landscapes in the warmer valleys typical of southern Idaho.  Popular hardy annuals suitable for Idaho include:

Common Name Scientific Name Regional Adaptation
Alyssum Lobularia maritime N, SW, SC, SE, HA
Calendula Calendula officicinalis N, SW, SC, SE, HA
Cornflower Centaurea cyanus N, SW, SC, SE, HA
Dianthus (China Pink) Dianthus chinensis N, SW, SC, SE, HA
Dusty Miller Senecio cineraria N, SW, SC, SE, HA
Kale (ornamental cabbage) Brassica oleracea N, SW, SC, SE, HA
Larkspur Consolida ambigua N, SW, SC, SE, HA
Pansy Viola wittrockiana N, SW, SC, SE, HA
Snapdragon Antirrhinum majus N, SW, SC, SE, HA
Sweet Pea Lathyrus oderatus N, SW, SC, SE, HA
Viola Viola cornuta N, SW, SC, SE, HA

Gaillardia Semi-hardy Annuals

These plants are not injured by light frost events (down to 28° F).  They can also tolerate cool weather, although many are adapted to hot summer conditions and will bloom all summer.  Semi-hardy annuals can help extend the season and provide color into the fall.  Popular semi-hardy annuals suitable for Idaho include:

Common Name Scientific Name Regional Adaptation
Carnation Dianthus caryophyllus N, SW, SC, SE, HA
Cosmos Cosmos dipinnatus N, SW, SC, SE, HA
Gaillardia (Blanket Flower) Gaillardia pulchella N, SW, SC, SE, HA
Gazania Gazania rigeas N, SW, SC, SE, HA
Moss Rose Portulaca grandiflora SW, SC, SE
Petunia Petunia spp. N, SW, SC, SE, HA
Phlox Phlox drummondii N, SW, SC, SE, HA
Rudbeckia Rudbeckia hirta N, SW, SC, SE, HA
Salvia Salvia spp. N, SW, SC, SE, HA
Sunflower Helianthus annuus N, SW, SC, SE, HA

BegoniaTender Annuals

These plants cannot withstand any frost an may not grow well during extended periods of cool weather.  Some of the tender annuals are actually perennials, but due to a lack of hardiness will only survive one summer in Idaho.  They can be planted only after the soil has warmed in the spring and will die back after the first frost of the fall, unless protected.  These plants are more suited to the warmer valleys of Idaho, although many can be planted in cooler areas if desired for a short season of summer color.  Popular tender annuals suitable for Idaho include:

Common Name Scientific Name Regional Adaptation
Ageratum Ageratum houstonianum N, SW, SC, SE
Amaranth (Love Lies Bleeding, Joseph’s Coat) Amaranthus spp. N, SW, SC, SE
Begonia Begonia x tuberhybrida N, SW, SC, SE
Celosia Celosia cristata N, SW, SC, SE
Chrysanthemum (annual) Chrysanthemum carinatum N, SW, SC, SE
Coleus Coleus x hybridus N, SW, SC, SE
Geranium Pelargonium hortorum N, SW, SC, SE, HA
Impatiens Impatiens wallerana N, SW, SC, SE
Marigold Tagetes patula N, SW, SC, SE, HA
Nicotiana (Flowering Tobacco) Nicotiana alata N, SW, SC, SE
Verbana Verbena x hybrida SW, SC
Zinnia Zinnia elegans N, SW, SC, SE

Key to regional adaptation notes:
N = Northern Idaho valley locations in USDA zones 5 & 6, Moscow to Sandpoint.
SE = Southeastern Idaho valley locations in USDA zones 3 & 4 from Rexburg to Pocatello. SC = South-central Idaho Magic Valley locations in USDA zones 4 & 5, Burley and Twin Falls.
SW = Southwestern Idaho Treasure Valley locations in USDA zones 5 & 6, Boise area (also Lewiston).
HA = High altitude (>5,000 ft) areas of central, southeastern Idaho and similar locations elsewhere.

Purdue University publishes a frost hardiness chart for annual flowers.

 August 16, 2012
Aug 162012
 

AsterSome annual flowers can withstand hot, dry growing conditions and still provide attractive foliage and/or flowers. These plants may find their best use in the warm valleys of southwestern Idaho, though they will grow well in many other places in the state.

Common Name Scientific Name Regional Adaptation
Amaranth, (Love Lies Bleeding, Joseph’s Coat) Amaranthus spp. N, SW, SC, SE, HA
California Poppy Eschscholzia californica N, SW, SC, SE, HA
Celosia (Cockscomb) Celosia cristata N, SW, SC, SE
Dusty Miller Senecio cineraria N, SW, SC, SE, HA
Four-O’clock Mirabilis jalapa N, SW, SC, SE
Gaillardia (Annual Blanket Flower) Gaillardia pulchella N, SW, SC, SE, HA
Gazania Gazania rigeas N, SW, SC, SE, HA
Larkspur Delphinium ajacis N, SW, SC, SE, HA
Moss Rose Portulaca grandiflora SW, SC, SE
Phlox Phlox drummondii N, SW, SC, SE, HA
Rudbeckia Rudbeckia hirta N, SW, SC, SE, HA
Salvia Salvia spp. N, SW, SC, SE, HA
Sunflower (ornamental) Helianthus annuus N, SW, SC, SE, HA
Zinnia Zinnia elegans N, SW, SC, SE

Key to regional adaptation notes:
N = Northern Idaho valley locations in USDA zones 5 & 6, Moscow to Sandpoint.
SE = Southeastern Idaho valley locations in USDA zones 3 & 4 from Rexburg to Pocatello. SC = South-central Idaho Magic Valley locations in USDA zones 4 & 5, Burley and Twin Falls.
SW = Southwestern Idaho Treasure Valley locations in USDA zones 5 & 6, Boise area (also Lewiston).
HA = High altitude (>5,000 ft) areas of central, southeastern Idaho and similar locations elsewhere.

 August 16, 2012
Aug 162012
 

PansyAnnual flowers differ in their ability to withstand shade while maintaining attractive foliage and producing blossoms. Most annuals require some full sunlight during the day, but here is a list of plants, suitable for Idaho, that can withstand part or full shade and still be attractive.

Common Name Scientific Name Regional Adaptation
Ageratum (P) Ageratum houstonianum N, SW, SC, SE, HA
Alyssum (P) Lobularia maritime N, SW, SC, SE, HA
Begonia (F) Begonia x tuberhybrida N, SW, SC, SE
Coleus (F) Coleus x hybridus N, SW, SC, SE
Fuschia (F) Fuschia x hybrida N, SW, SC, SE
Impatiens (F) Impatiens spp. N, SW, SC, SE
Nicotiana (Flowering Tobacco) (P) Nicotiana alata N, SW, SC, SE
Pansy (P) Viola spp. N, SW, SC, SE, HA
Snapdragon (P) Antirrhinum majus N, SW, SC, SE, HA

(P) = Tolerates dappled or part-shade conditions.
(F) = Tolerates full shade conditions.

Key to regional adaptation notes:
N = Northern Idaho valley locations in USDA zones 5 & 6, Moscow to Sandpoint.
SE = Southeastern Idaho valley locations in USDA zones 3 & 4 from Rexburg to Pocatello. SC = South-central Idaho Magic Valley locations in USDA zones 4 & 5, Burley and Twin Falls.
SW = Southwestern Idaho Treasure Valley locations in USDA zones 5 & 6, Boise area (also Lewiston).
HA = High altitude (>5,000 ft) areas of central, southeastern Idaho and similar locations elsewhere.

 August 16, 2012
Aug 162012
 

CarnationMany annuals add scent to the landscape. The following annual plants provide not only the beauty of blooms, but provide pleasant fragrance for the garden. Try them in pots or beds near patios, balconies or other places you’re likely to frequent.

Common Name Scientific Name Regional Adaptation
Alyssum (P) Lobularia maritime N, SW, SC, SE, HA
Carnation (annual) Dianthus caryophyllus N, SW, SC, SE, HA
Mooonflower Ipomea alba N, SW, SC, SE
Nicotiana (Flowering Tobacco) Nicotiana alata N, SW, SC, SE
Pincushion Flower Scabiosa atropurpurea N, SW, SC, SE, HA
Scented Geranium Pelargonium sp. N, SW, SC, SE, HA
Sweet Pea Lathyrus oderata N, SW, SC, SE, HA
Sweet Sultan Centaurea moschata SW, SC
Verbena Verbena x hybrida SW, SC
Wallflower Cheiranthus cheiri N, SW, SC, SE, HA

Key to regional adaptation notes:
N = Northern Idaho valley locations in USDA zones 5 & 6, Moscow to Sandpoint.
SE = Southeastern Idaho valley locations in USDA zones 3 & 4 from Rexburg to Pocatello. SC = South-central Idaho Magic Valley locations in USDA zones 4 & 5, Burley and Twin Falls.
SW = Southwestern Idaho Treasure Valley locations in USDA zones 5 & 6, Boise area (also Lewiston).
HA = High altitude (>5,000 ft) areas of central, southeastern Idaho and similar locations elsewhere.

 August 16, 2012
Aug 162012
 

ColeusSeveral species of annuals have attractive or interesting foliage that is of greater ornamental value than the flowers. These have a unique place in the landscape and container plantings and provide interest throughout the growing season, not just during the period of bloom. Most of these plants are tender annuals and grow best where the frost-free season is relatively long. Exceptions are ornamental kale and dusty miller.

Common Name Scientific Name Regional Adaptation
Amaranth, (Joseph’s Coat) Amaranthus spp. N, SW, SC, SE
Begonia Begonia x tuberhybrida N, SW, SC, SE
Caladium Caladium x hortulanium N, SW, SC, SE
Coleus Coleus x hybridus N, SW, SC, SE
Dusty Miller Senecio cineraria N, SW, SC, SE, HA
Geranium Pelargonium hortorum N, SW, SC, SE, HA
Impatiens Impatiens wallerana N, SW, SC, SE
Ornamental Kale Brassica oleracea N, SW, SC, SE, HA

Key to regional adaptation notes:
N = Northern Idaho valley locations in USDA zones 5 & 6, Moscow to Sandpoint.
SE = Southeastern Idaho valley locations in USDA zones 3 & 4 from Rexburg to Pocatello.
SC = South-central Idaho Magic Valley locations in USDA zones 4 & 5, Burley and Twin Falls.
SW = Southwestern Idaho Treasure Valley locations in USDA zones 5 & 6, Boise area (also Lewiston).
HA = High altitude (>5,000 ft) areas of central, southeastern Idaho and similar locations elsewhere.

 August 16, 2012
Aug 162012
 

Morning gloryAlthough most vines are woody or perennial, a few annuals can also be used in situations best filled by plants that reach heights of at least four feet and self-attach. Here are a few that can be successfully grown in Idaho. Most adapt better to warm regions rather than colder, high elevations areas. There are exceptions, such as sweet peas.

Common Name Scientific Name Regional Adaptation
Black-eyed Susan Vine Thunbergia alata N, SW, SC, SE, HA
Canary Bird Flower Tropaeolum peregrinum N, SW, SC, SE
Cardinal Climber Quamoclit sloteri N, SW, SC, SE
Climbing Nasturtium Tropaeolum majus N, SW, SC, SE
Moonflower Ipomoea alba N, SW, SC, SE
Morning Glory* Ipomea purpurea N, SW, SC, SE
Scarlet Runner Bean Phaseolus coccineus SW, SC
Sweet Pea Lathyrus oderatus N, SW, SC, SE, HA

*Ipomea is not invasive like field bindweed, which is sometimes incorrectly called “Morning Glory.”

Key to regional adaptation notes:
N = Northern Idaho valley locations in USDA zones 5 & 6, Moscow to Sandpoint.
SE = Southeastern Idaho valley locations in USDA zones 3 & 4 from Rexburg to Pocatello.
SC = South-central Idaho Magic Valley locations in USDA zones 4 & 5, Burley and Twin Falls.
SW = Southwestern Idaho Treasure Valley locations in USDA zones 5 & 6, Boise area (also Lewiston).
HA = High altitude (>5,000 ft) areas of central, southeastern Idaho and similar locations elsewhere.

For more discussion on vining and climbing annuals, see the web site by Colorado Master Gardener Judy Sedbrook.

 August 16, 2012
Aug 162012
 

Hanging basket of pink petuniasMany annuals have appropriate form and flowering habit to enhance the appearance of hanging baskets or containers. This list is only the beginning. The use of baskets and pots can improve the appearance of barren area in the landscape, regardless of growing region. Click here to access more information on container gardening.

Common Name Scientific Name Regional Adaptation
Alyssum Lobularia maritime N, SW, SC, SE, HA
Black-eyed Susan Vine Thunbergia alata N, SW, SC, SE, HA
Dwarf Morning Glory Convolvulus tricolor SW, SC, SE
Coleus Coleus x hybridus N, SW, SC, SE
Fuschia Fuschia x hybrida N, SW, SC, SE
Impatiens Impatiens spp. N, SW, SC, SE
Ivy Geranium Pelargonium peltatum N, SW, SC, SE, HA
Lobelia Lobelia erinus N, SW, SC, SE, HA
Mandevilla Mandevilla splendens N, SW, SC, SE, HA
Million Bells Petunia Calibrachoa N, SW, SC, SE, HA
Periwinkle Catharanthus roseus N, SW, SC, SE, HA
Petunia Petunia spp. N, SW, SC, SE, HA
Sapphire Flower Browallia viscose N, SW, SC, SE, HA

 

Key to regional adaptation notes:
N = Northern Idaho valley locations in USDA zones 5 & 6, Moscow to Sandpoint.
SE = Southeastern Idaho valley locations in USDA zones 3 & 4 from Rexburg to Pocatello. SC = South-central Idaho Magic Valley locations in USDA zones 4 & 5, Burley and Twin Falls.
SW = Southwestern Idaho Treasure Valley locations in USDA zones 5 & 6, Boise area (also Lewiston).
HA = High altitude (>5,000 ft) areas of central, southeastern Idaho and similar locations elsewhere.

 

 

 August 16, 2012
Aug 162012
 

Baby's breathMany annuals not only provide color in the garden, but look attractive and last well as cut flowers. Some, such as baby’s breath, cockscomb, globe amaranth, statice, bells of Ireland, and strawflower also make attractive dried arrangements.

For more information about growing cut flowers commercially, try the University of Idaho Extension publication Specialty Cut Flower Production.

 

Common Name Scientific Name Regional Adaptation
Amaranth, (Love Lies Bleeding) Amaranthus spp. N, SW, SC, SE, HA
Carnation (annual) Dianthus caryophyllus N, SW, SC, SE, HA
Baby’s Breath Gysophila elegans N, SW, SC, SE, HA
Bells of Ireland Moluccella laevis N, SW, SC, SE, HA
Celosia (Cockscomb) Celosia cristata N, SW, SC, SE
China Aster Callistephus spp. N, SW, SC, SE, HA
Cornflower Centarea cyanus N, SW, SC, SE, HA
Cosmos Cosmos spp. N, SW, SC, SE, HA
Gaillardia Gaillardia spp. N, SW, SC, SE, HA
Globe Amaranth Gomphrena globosis N, SW, SC, SE, HA
Larkspur Delphinium ajacis N, SW, SC, SE, HA
Nasturtium Tropaeolum majus N, SW, SC, SE, HA
Marigold Tagetes spp. N, SW, SC, SE, HA
Salvia Salvia spp. N, SW, SC, SE, HA
Snapdragon Antirrhinum majus N, SW, SC, SE, HA
Statice Limonium sinuatum N, SW, SC, SE, HA
Sunflower Helianthus annuus N, SW, SC, SE, HA
Zinnia Zinnia elegans N, SW, SC, SE

 

cut flower arrangementKey to regional adaptation notes:
N = Northern Idaho valley locations in USDA zones 5 & 6, Moscow to Sandpoint.
SE = Southeastern Idaho valley locations in USDA zones 3 & 4 from Rexburg to Pocatello.
SC = South-central Idaho Magic Valley locations in USDA zones 4 & 5, Burley and Twin Falls.
SW = Southwestern Idaho Treasure Valley locations in USDA zones 5 & 6, Boise area (also Lewiston).
HA = High altitude (>5,000 ft) areas of central, southeastern Idaho and similar locations elsewhere.

 August 16, 2012
Aug 162012
 

transplanting a seedlingSoil preparation is critical to success with annuals. Proper site and soil preparation will ensure a healthy environment for annual flowers. First, make sure the site has good quality topsoil. This may require addition of topsoil, particularly in new home sites. Amend the soil by adding 3-5 inches of well-aged compost or manure. This is especially important in the arid, calcareous soils of southern Idaho. Add the equivalent of 5 lb/1000 sq. ft. of nitrogen in the form of a complete fertilizer, such as 5-10-5. The fertilizer choice should be high in phosphorus and should preferably include sulfur. After amendments are added, the soil should be tilled to a depth of at least 8 inches, leveled, and smoothed (but not packed). Just prior too or after planting, it is a good idea to add two or three inches of mulch (wood chips, bark, etc.) to the soil surface.

 August 16, 2012
Aug 162012
 

Three options exist for starting annual plants. They are:

  1. direct seeding,
  2. indoor seeding and transplanting, and
  3. purchasing and transplanting bedding plants.
Direct Seeding

The simplest and cheapest propagation method is to plant seed directly into the garden site. A wider array of species and varieties are available as seed, providing the gardener with greater choice. The advantages of direct seeding are offset by the tendency for plants to be slow and erratic with respect to emergence and early growth. This may delay flowering and shorten the color display during the blooming period. This is especially true in the short growing season areas of Idaho’s mountainous regions.

Refer to the seed package for recommended date of planting. Plant seed where you would like the flowers to grow in the garden. Place seed in shallow trenches and cover lightly. Plant extra seed and thin after emergence, if necessary. Refer to the seed package again to determine seeding rate and depth. Maintain good moisture at the soil surface by misting lightly until the plants emerge. Once established, deeper irrigation should be applied after the top 1-2 in. of soil dries out.

Indoor Seeding

Growing your own transplants has the best features of both direct seeding and purchase of transplants. It gives the cost advantage and plant choice of direct seeding while making it possible to get a head start on the growing season.

The key to success is providing appropriate conditions for germination and early growth of the new seedlings. Soil, temperature, light, and moisture are the most important elements. The soil medium must be free of disease organisms that may cause death of germinating plants. The best soil medium is a commercial potting soil. Containers may range from recycled plastic pots, paper cups, or commercial seed plug trays. Wash and disinfect all containers before using. Temperatures should be warm enough to allow germination (e.g. 60-75º F during the day and slightly cooler at night).

Unless a greenhouse is available, artificial lighting will be required. Even a south facing window does not supply young plants with enough light to keep them from getting ‘leggy’ and weak. Some seedlings may need as much as 18 hours of light to be healthy. Fancy equipment and expensive “grow lights” are not necessary. A standard fluorescent shop light, easily found at home improvement and hardware stores, fitted with one “warm,” and one “cool” tube works very well. Suspend the light fixture 12-18 inches from the plants and raise as growth occurs. It is also important to keep soil moisture balanced between too wet and too dry. This required frequent, light irrigations.

Another important process in producing healthy transplants is called hardening off. This refers to the procedure of adapting the plants to outdoor conditions to reduce transplant shock. This can be done by placing the plants outdoors in full sun for increasing amounts of time each day for a week or ten days prior to planting. Hardening the plants will improve survival and increase the early growth rate. Those fortunate enough to have a cold frame or unheated greenhouse can use these structures for this purpose as well as starting seeds.

Purchasing Bedding Plants

Buying partially-grown plants is the easiest and quickest way to establish annual flowers. It is also the most expensive and provides the least in the way of plant choice. But, transplants will result in quicker blooms and longer flowering periods.

When choosing transplants, it is best to buy from a nursery or garden store having personnel knowledgeable about local growing conditions. This will assure availability of adapted species and varieties. Do not look for the largest plants or necessarily, those in bloom. Seek plants with good dark green color, healthy root systems, and no sign of disease or pest problems. Try to find plants that have been hardened off, in order to aid the transition to the yard.

Another important consideration for growing transplants is the timing initial planting. To properly make this decision for a particular flower, it is essential to know the amount of time needed to produce a transplant and the approximate date of intended transplanting outside.

Transplanting

Whether transplants are purchased or self-grown, the process for placing them outside is the same. The first decision is deciding when to place the plants outdoors. Transplanting date is based on the date of last frost in a given area. Tender annuals should not be planted to the garden until 1 to 2 weeks after the average last frost date. It is, after all, an average and frost will commonly occur after the printed date.

To estimate the last frost date in your area, look at the Idaho chart compiled by Ed Hume Seeds.

Tonie Fitzgerald, from the Spokane, Washington County Extension office compiled a table listing appropriate dates for planting and/or transplanting common annual flowers. The dates should be reasonably accurate for much of northern and south-central Idaho. Dates for the Treasure Valley of southwestern Idaho will be 2-3 weeks earlier, southeastern Idaho a few days later, and the high country up to 2 weeks later.

frost damage

Frost can damage seedlings or transplants

It is best to transplant on a cool, cloudy day with little wind. This will allow acclimation under conditions of limited water loss. After removing a plant from its container, tease roots away from the surface of the root ball. Don’t plant the seedlings too deep. Bury the root ball in a hole sufficiently deep only to bring the soil slightly above the pot soil level. Space the plants according to the instruction on the seed packet or nursery pot label. For the first 7-10 days, water the plants frequently and lightly. Remember that early on the pot soil holds all of the roots and is the only source of water. The root ball will need to be wetted as often as it would in the pot until the roots can grow into the surrounding soil.

 August 16, 2012
Aug 162012
 
Aphids

Also known as plant lice, aphids are small, soft-bodied, sucking insects that cluster on the stems or underside of leaves. Aphids are usually wingless and green, brown, or black in color. Symptoms of infested plants include distorted or curled leaves, presence of sticky sap (honeydew) on the infested surfaces, and misshapen new growth.

Aphids can be controlled with the use of insecticidal soap or a registered insecticide. A strong stream of water directed at the infected plants may knock aphids from the plant. Many beneficial insects such as ladybeetles and lacewings feed on aphids and if an infestation is not too severe, it may be appropriate to be patient and let nature take its course.

Caterpillars

Caterpillars can quickly damage annual plants

Caterpillars

Larvae of numerous species of moths and butterflies. These voracious creatures come in many sizes and colors. Plant symptoms include chewed or completely missing leaves. Some types of caterpillars will roll or fold the leaves and hide inside. Often, frass (droppings) are present on and around the plants.

A light infestation can be easily controlled by picking larvae from the plant and crushing them. Common registered insecticides will effectively kill caterpillars.

Grubs and Cutworms

Grubs and cutworms are the larval stage of many moths and beetles. Most live in the soil and feed on roots or emerge at night to feed on stems and foliage. Severely damaged plants may die from having the stem or roots severed. Other symptoms include chewed lower leaves and/or wilted or stunted plants that result from root feeding.

Grubs and cutworms can be controlled by handpicking, or using a soil drench of an approved insecticide.

Leafminers

Leafminers are small insect larvae that burrow under the leaf surface while feeding. Symptoms are easily recognized and exhibit themselves as zig-zag or wandering lines on the upper leaf surface that are lighter in color that the rest of the leaf surface. These are tunnels in the leaves caused by leafminer feeding.

A light infestation of leafminers can be controlled by removing and destroying damaged leaves. A heavy infestation will require the use of a registered systemic type insecticide.

Sometimes covering a crop with a floating row cover will exclude the insects from entering the plant.

Mealybugs

Mealybugs are sucking insects that infest stems of many plants. Mealybugs are easily recognized by the presence of a cotton-like white substance they deposit for protection.

Control of mealybugs can be had by spraying the plants with a direct stream of water, using an insecticidal soap, or applying a registered insecticide.

Spider Mites

Not actually insects, these miniscule pests are related to spiders. They spin protective webs on the underside of leaves and feed by sucking juice from the leaves. Symptoms include color mottling that, at a distance, may appear as a general yellowing of older leaves. Webbing will be present on the underside of infested leaves. The mites, to small to be easily visible, can be detected by shaking a leaf over piece of clean white paper.

Spider mites prefer dry, dusty environments. Sprinkler irrigation or routine washing of leaves with water usually keep them at bay. A severe infestation may require the use of a registered miticide. Most common insecticides are ineffective against spider mites.

slug

Slugs prefer damp places in the garden

Slugs and Snails

Slugs and snails prefer damp soil and humid conditions. Slugs and snails often hide during the day and feed at night. Symptoms include chewed leafs and glistening slime trails on plant surfaces.

Control snails and slugs with baits.

Thrips

Damage is caused by the larva of this small, four-winged insect. Thrips reside on the underside of leaves and use their rasping mouthparts to scrape away the surface of the leaf after which they feed on the sap. Symptoms appear as small white streaks and blotches, more prominent on the underside of the leaf.

A light infestation does little permanent damage to the plant and can be ignored. A heavy infestation will likely require the use of a registered insecticide.

Whiteflies

In Idaho, whiteflies are more commonly a problem in greenhouses than they are outdoors. They are small insects with distinct bright white wings that reside and feed on the underside of leaves. Symptoms include the presence of honeydew on leaf surfaces, often accompanied by a black sooty mold. When disturbed, clouds of the white, rapidly flying insects will rise above the foliage, then quickly resettle.

Trap the flies with yellow sticky boards or use a registered insecticide.

 August 16, 2012
Aug 162012
 
Damping off

Damping off disease of seedlings © 2004 Cornell Plant Pathology Herbarium

Damping Off

Damping off is caused by fungal pathogens that infect seedlings at soil level, girdling the stems and causing death. Infected seedling will develop tan-colored, soft tissue at the base of the stem. The plants fall over and usually die. Once established and actively growing, plants are seldom affected by damping off. Control measures include maintaining optimum soil moisture and planting into well-drained soils that are not overly wet. Maintaining air circulation is important. In extreme cases, a soil drench of a registered fungicide can be applied to the soil surface. However, by the time damage is observed it may be too late for effective control.

Leaf Spots

Leaf spots are caused by numerous fungal (occasionally bacterial) pathogens that penetrate and kill leaf tissue. Symptoms usually start and are worse on older leaves. These diseases are usually worse following periods of wet weather and high humidity.

Removal of all dead plant material at the end of the growing season helps prevent many leaf spot diseases the following year. In-season control usually requires use of a registered fungicide.

Powdery Mildew

Powdery mildew is caused by fungal pathogens. The classic symptom is a whitish, powdery growth present on leaf surfaces. Heavy infections cause distortions on new growth. Infections are often worse during summers preceded by damp spring weather. Plants grown in shade are more prone to infection with powdery mildew

Prevention involves growing plants in a sunny location and making sure there is plenty of space and air movement around plants. Control of severe infections may require the use of a registered fungicide.

Root and Stem Rots

Root and stem rots are caused by fungi (occasionally bacteria) that live in the soil. Infected plants initially develop mild wilting symptoms that become progressively worse and may eventually cause death.

Soil pathogens are difficult to control. They can best be prevented by planting resistant varieties, avoiding overly wet soil conditions, and destroying infected plants.

White Mold

White mold is caused by a fungus that overwinters in the soil. It infects plant stems that touch moist soil surfaces. Symptoms include a slimy, white mold that girdles and collapses the infected tissue. Leaves above the girdled stem wilt and die. In advanced stages, small gray structures that look like mouse droppings form inside a hollowed stem.

Prevention is the best strategy and involves staking stems off the ground, spacing plants to allow air movement around foliage, and irrigating infrequently to allow intermittent drying of the soil surface.

Virus

Not technically alive, viruses are small pieces of genetic material that disrupt plant function. Symptoms vary widely and usually include some combination of stunting, yellowing, mottling, or leaf and stem distortion.

Consistently effective control measures for viruses are rare. The best methods include using resistant varieties or preventing the infestation of organisms (usually insects) that transfer the viruses from one plant to another. Prevention also involves removing and destroying any infected plants.

For a more complete discussion of care for annual flowers, including selection, planting, general management, and pest control, see chapter 19 of the Idaho Master Gardener Handbook.

Additional information on insect and disease management in annuals is provided in this list of publications from the University of Georgia.

Diagnosis information and specific control measures for diseases in the landscape is available from the University of Kentucky.

 August 16, 2012
Aug 162012
 

Most weed problems in lawns are associated with a weak, thin turf. A thin turf is easily pushed aside by aggressive weeds which can become worse over time. Make sure to follow good fertilization, irrigation and mowing guidelines to build a thick, vigorously growing lawn. Heavy weed populations are usually an indication of some other inherent problem with the lawn.

Some perennial weeds, like white clover, can still become problems even in well managed lawns. Many herbicides are available to effectively control weeds in lawns, but their success largely depends on proper application, and perhaps more importantly, on correct timing. Knowing what weeds you have will help you determine the best time of the year to control them.

Realize that it is impossible to eradicate all weeds from a lawn even with herbicide use. Learn to tolerate some weeds in your lawn and avoid indiscriminate use of herbicides which can injure trees, surrounding landscape plants and even the lawn itself.

Photographs of many weeds can be found at WSSA’s Photo Gallery.

Perennial Broadleaf Weeds

Some common perennial broadleaf weeds in home lawns include dandelion, field bindweed (also called morningglory), white clover, curly dock, ground ivy, Canada thistle, broadleaf plantain, buckhorn plantain and yarrow. Make sure to properly identify the weeds before choosing herbicides for control. University of Idaho extension educators, master gardeners and nursery personnel can help you with correct identification.

Broadleaf weeds can be controlled with postemergence herbicides (a chemical that is applied to weeds after the weeds have emerged from the soil) which kill weeds that are actively growing. Postemergence herbicides do not prevent weeds from germinating.

The best time of the year to control perennial weeds is in late summer or early fall when the weeds are preparing for winter. In preparation for winter, perennial weeds move energy reserves from the leaves to underground stems and roots, so a herbicide application at this time will ensure movement of the herbicide to these plant parts, thus resulting in a more effective kill because the roots are being affected. Spring applications to perennial weeds can slow their growth and may kill them, but it is more difficult. Regardless of when applications are made, make sure the weeds are actively growing at time of application. Avoid mowing for 1 to 2 days before and after the application to ensure maximum uptake of the herbicide by the weeds.

There are many broadleaf weed control products available for home use. These products will contain one or a combination of the following chemicals: 2,4-D, 2,4-DP, MCPP, MCPA and dicamba. They are safe to use on cool-season lawn grasses. Liquid and granular formulations of these chemicals are available. It is very important to properly calibrate sprayers or granular spreaders to ensure accurate, uniform application and avoid spraying adjacent flower beds or susceptible plants. Be sure to read and follow all label directions.

Perennial Grassy Weeds

Perennial grassy weeds are the most difficult weeds to control in a home lawn. Some common perennial grassy weeds include quackgrass, roughstalk bluegrass, smooth bromegrass, annual bluegrass (there exist some perennial biotypes) and even other cool-season grasses such as tall fescue and creeping bentgrass. There are essentially no herbicides available for the selective control of these weeds in a lawn. Removal of these problem weedy grasses prior to establishing a lawn and the use of high quality seed or sod is essential to preventing these weeds from becoming a problem. Many home lawns are established with poor quality seed that has high amounts of weeds such as annual bluegrass and roughstalk bluegrass. What is contained in a seed lot you are considering to purchase is readily available on the seed label, but most homeowners are unaware of its importance. If small patches of perennial grasses are found in a lawn, physical removal with a shovel or spraying with a non-selective herbicide such as glyphosate is the only option followed by re-seeding or sodding the bare areas.

Annual Grassy Weeds

Weeds like crabgrass and foxtail are warm-season grasses that germinate from seed in the spring and infest lawns during the hot days of summer. They tend to invade lawns along sidewalks and driveways where temperatures are hottest and lawns are thin. Thick, vigorously growing lawns will out-compete most annual grassy weeds.

Annual grassy weeds are best controlled with pre-emergence herbicides (a chemical that is applied before the seeds have germinated) which kill germinating weeds. These herbicides must be applied well before the weeds germinate since they will not kill weeds once they have emerged. Additionally, some of these pre-emergence herbicides are impregnated on fertilizer granules and applied as a weed and feed. Crabgrass will germinate when soil temperatures reach 55 to 60º F. This occurs around mid-March to early April for the Treasure Valley, Magic Valley and northern Idaho and late March to mid-April for central and eastern Idaho.

There are some herbicides that will kill young annual grasssy weeds, but they usually only work well on very young plants so application timing is critical.

Do not overseed into areas that have recently been treated with pre-emergence herbicides because the chemical will kill emerging lawn grasses as well. Check the label of the herbicide to see how long you need to wait before planting into an area treated with a pre-emergence herbicide.

 August 16, 2012
Aug 132012
 

herb leaves in a basketAnnual herbs produce foliage, flowers and seed in one season before succumbing to fall frosts. Popular examples include basil, chervil, cilantro and dill. These annual herbs generally require more water and fertilizer than woodier perennials. If allowed to flower and set seed, many annual herbs will re-seed themselves in the garden.

Try putting in several plantings of these herbs to keep your kitchen stocked all summer long.


Annual Herbs
Name of Annual Herb Height/Spread Suitable for Containers? How Propagated* Primary Uses**
Basil
Ocimum basilicum
8-24″ x 6-12″ depending on cultivar Yes Seed or cuttings leaves in pesto, salad, pizza, vinegars, teas
Borage
Borage officinalis
1-3′ x 12″ No Seed edible flowers, leaves in sandwiches, salads, teas
Chamomile, German
Matricaria recutita
2.5″ x 4-6″ Yes Seed teas, bath herbs, soaps, sachets
Chervil
Anthriscus cerefolium
2″ x 15″ Yes Seed leaves in salads, soups, butters, sauces, teas
Cilantro (Coriander seed)
Coriandrum sativum
24″ x 18″ Yes Seed leaves in salsa, salads, seeds in meat dishes
Dill
Anethum graveolens
5′ x 12″ No Seed salads, breads, soups, pickles, vinegars
Parsley
(biannual, grow as annual)
Petroselinum crispum
6″ x 2′ Yes Seed garnish, salads, eggs, soups, meats, pesto, vegetable dishes, breads
Summer Savory
Satureja hortensis
18″ x 12″ Yes Seed or cuttings meat rub, soups, salads

* Easy to follow directions for propagating herbs by seed, cuttings or division are found in the University of Missouri Extension Publication Growing Herbs at Home, available free online
**Some information in this table on herb uses provided by Cornell University’s Growing Herbs for the Home Gardener


 August 13, 2012