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Aug 172012
 

Bulbs can be categorized into groups, based on growth characteristics or intended use, making selection easier. Useful groupings include season of bloom and hardiness.


Daffodils

Daffodils are among the favorite spring bulbs

Spring Flowering Bulbs

When considering bulbs, most people think of the common spring blooming flowers, including the crocus, daffodil, and tulip. These are plants that emerge relatively early in the spring, bloom for a short period of time, then die back and wait for next spring to repeat the process. These bulbs are usually hardy under most Idaho conditions and once planted need minimal care. Spring bulbs suitable for planting in Idaho include:

Common Name
Scientific Name
Relative Bloom Time
Regional Adaptation
Anemone Anemone Blanda Mid-spring N, SW, SC
Cammassia Cammassia leichtlinii Late spring N, SW, SC, SE
Chionodoxa Chionodoxa forbesii Early spring N, SW, SC, SE, HA
Crocus Crocus spp. Very early to mid-spring N, SW, SC, SE, HA
Daffodil Narcissus spp. Early to late spring N, SW, SC, SE, HA
Fritillaria Fritillaria spp. Mid-spring N, SW, SC, SE
Grape Hyacinth Muscari armeniacum Early to mid-spring N, SW, SC, SE, HA
Hyacinth Hyacithus orientalis Early spring N, SW, SC
Iris Iris spp. Late spring N, SW, SC, SE
Leucojum Leucojum aestivum Mid-springm N, SW, SC, SE
Ornamental Onion Allium spp. Late spring N, SW, SC, SE
Ornithogalum Ornithogalum umbellatum Late spring N, SW, SC
Pink Buttercups Oxalis adenophylla Late spring N, SW, SC
Puschkinia Puschkinia libanotica Mid-spring N, SW, SC, SE, HA
Snowdrops Galanthus nivalis Very early spring N, SW, SC, SE, HA
Squill scilla siberica Early to late spring N, SW, SC, SE, HA
Tulip Tulipa spp. Mid to late spring N, SW, SC, SE, HA
Trout Lily Erythronium spp. Mid-spring N, SW, SC, SE, HA
Winter Aconite Eranthis cilicium Very early spring 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.


lily

Many lily species grow well in Idaho

Summer Flowering Bulbs

Summer bulbs provide color after the spring flowers have stopped blooming. Many of them bridge the gap between spring bulbs and other perennials. Others bloom late into the summer. Summer bulbs are a mixture of those hardy in Idaho and those that are not hardy and must be treated as annuals. Non-hardy bulbs can be unearthed and stored for replanting the next year. Most of the tender summer bulbs are not recommended for planting in the shortest season areas of Idaho because of the potential for frost injury. For more information on storing tender bulbs overwinter, view this North Dakota Extension article.

Common Name
Scientific Name
Relative Bloom Time
Regional Adaptation
Bulbs Hardy in Idaho*
Arum Arum italicum Early Summer N, SW
Brodiaea Brodiaea laxa Early summer N, SW
Foxtail Lily Eremurus spp. Early summer N, SW, SC
Hardy Gladiolus Gladiolus nanus Mid-summer N, SW, SC, SE
Iris Iris spp. Early summer N, SW, SC, SE
Ixiolirion Ixiolirion pallasii Early summer N, SW, SC
Lily Lillium spp. Early to late summer N, SW, SC, SE
Ornamental Onion Alliums spp. Early summer N, SW, SC, SE
Ornithogalum Ornithogalum umbellatum Early summer N, SW, SC
Peonies Paeonia x hybrida Early summer N, SW, SC, SE, HA
Tender Summer Bulbs Grown as Annuals*
Begonia Begonia spp. Mid to late summer N, SW, SC, SE
Canna Canna spp. Late summer N, SW, SC, SE
Caladium Caladium spp. (colorful foliage) N, SW, SC, SE
Dahlia Dahlia spp. Mid-summer N, SW, SC, SE, HA
Gladiola Gladiolus spp. Early summer N, SW, SC, SE, HA

*Hardy summer bulbs can be planted permanently into the garden, tender bulbs must be handled like annuals with the bulbs being harvested and stored indoors during the winter months.

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.

Caladiums

Caladiums provide great summer foliage color


Fall Flowering Bulbs

A few bulbs bloom during the fall season. Those listed below are hardy in Idaho and include:

Common Name
Scientific Name
Relative Bloom Time
Regional Adaptation
Colchicum Colchicum autumnalis Late Fall N, SW, SC
Crocus (late types) Crocus spp. Late Fall N, SW, SC, SE
Hardy Cyclamen Cyclamen spp. Mid Fall N, SW, SC, SE
Lily Lillium spp. Mid Fall 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.

Crocus

Some Crocus species bloom in the fall


The International Bulb Society has constructed a picture gallery that includes most of the worlds bulb propagated plants.

A fact sheet from North Carolina State University provides assistance with selection of bulb plants.

 August 17, 2012
Aug 172012
 

Most perennials do not bloom throughout an entire growing season. Knowing the period of bloom will help with determination of plant combinations that provide color all summer long. Below are lists of perennials classified by their flowering time. The dates are approximate and will depend on geographical location. The warmer valleys of Idaho may provide blooming conditions for many plants as much as 6 weeks earlier than the cooler northern or mountainous regions.


Gaillardia

Blanket Flower blooms all summer

Perennials with Extended Blooming Times

These are the exceptional plants that bloom over several months through spring, summer, and fall.

Common Name Scientific Name Regional Adaptation
Anthemis (Dyer’s Chamomile) Anthemis tinctoria N, SW, SC, SE, HA
Aster Aster spp. N, SW, SC, SE, HA
Balloon Flower Platycodon grandiflorus N, SW, SC, SE, HA
Bee Balm Monarda didyma N, SW, SC, SE, HA
Bellflower Campanula spp. N, SW, SC, SE, HA
Blanket Flower Gaillardia . grandiflora N, SW, SC, SE, HA
Butterfly Weed Asclepias tuberose N, SW, SC, SE, HA
Cranesbill Geranium spp. N, SW, SC, SE, HA
Deadnettle Lamium maculatum N, SW, SC, SE, HA
Dianthus Dianthus spp. N, SW, SC, SE, HA
Flax Linum perenne, Linum grandiflorum N, SW, SC, SE, HA
Hollyhock Alcea rosea N, SW, SC, SE, HA
Lavender Lavendula angustifolia SW, SC
Pincushion Flower Scabiosa caucasica N, SW, SC, SE, HA
Potentilla Potentilla verna N, SW, SC, SE, HA
Russian Sage Perovskia atriplicifolia SW, SC
Shasta Daisy Leucanthemum x supermum N, SW, SC, SE, HA
Veronica Veronica spp. N, SW, SC, SE
Yarrow Achillea spp. 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.


Poppies

Poppies provide spring color. Courtesy of FreeFoto.com

Early-Blooming Perennials

These are plants that bloom in early spring, typically March (warm areas), April, and May.

Common Name Scientific Name Regional Adaptation
Bleeding Heart Dicentra spp. N, SW, SC, SE, HA
Bloodroot Sanguinaria canadensis N, SW, SC, SE, HA
Blue False Indigo Baptisia australis N, SW, SC, SE, HA
Bugleweed Ajuga reptans N, SW, SC, SE, HA
Candytuft Iberis sempervirens N, SW, SC, SE
Columbine Aquilegia spp. N, SW, SC, SE, HA
Delphinium Delphinium x elatum N, SW, SC, SE, HA
Dianthus Dianthus plumarius N, SW, SC, SE, HA
False Rock Cress Abrietia deltoidea N, SW, SC
Forget-Me-Not Anchusa myosotis N, SW, SC, SE, HA
Gas Plant Dictamnus albus N, SW, SC, SE, HA
Jacob’s Ladder Polemonium reptans N, SW, SC, SE, HA
Mountain Bluet Centaurea montana N, SW, SC, SE
Oriental Poppy Papaver orientalis N, SW, SC, SE, HA
Peony Paeonia spp. N, SW, SC, SE, HA
Phlox, Creeping Phlox subulata N, SW, SC, SE, HA
Prairie Smoke Geum triflorum N, SW, SC, SE, HA
Pussytoes Antennaria dioica N, SW, SC, SE, HA
Rock Cress Arabis caucasica N, SW, SC, SE, HA
Sea Pink (Sand Wort) Armeria maritime N, SW, SC, SE, HA
Snow-in-Summer Cerastium tomentosum 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.


Asters

One of many summer blooming asters

Mid-Season Perennials

These are plants that bloom during the mid-summer months, typically June, July, and into August.

Common Name Scientific Name Regional Adaptation
Alumroot (Coral Bells) Heuchera sanguinea N, SW, SC, SE, HA
Aster Aster spp. N, SW, SC, SE, HA
Astilbe Astilbe x arendsii N, SW, SC, SE
Bee Balm Monarda didyma N, SW, SC, SE
Bellflower Campanula spp. N, SW, SC, SE, HA
Blanket Flower Gaillardia . grandiflora N, SW, SC, SE, HA
Butterfly Weed Asclepias tuberose N, SW, SC, SE, HA
Cardinal Flower Lobelia cardinalis N, SW, SC, SE, HA
Chrysanthemum Deudranthuna x grandiflora N, SW, SC, SE, HA
Deadnettle Lamium maculatum N, SW, SC, SE, HA
Coreopsis Coreopsis spp. N, SW, SC, SE
Flax Linum perenne N, SW, SC, SE, HA
Foxglove Digitalis purpurea N, SW, SC, SE
Gloriosa Daisy Rudbeckia x hybrida N, SW, SC, SE, HA
Goatsbeard Aruncus dioicus N, SW, SC, SE
Hollyhock Alcea rosea N, SW, SC, SE, HA
Larkspur Delphinium spp. N, SW, SC, SE, HA
Lavendar Lavandula angustifolia SW, SC
Lupine Lupinus spp. N, SW, SC, SE, HA
Penstemon Penstemon spp. N, SW, SC, SE, HA
Phlox Phlox spp. N, SW, SC, SE, HA
Pincushion Flower Scabiosa caucasica N, SW, SC, SE, HA
Red Valerian Centranthus rubber SW, SC
Russian Sage Perovskia atriplicifolia SW, SC
Sage Salvia officinalis N, SW, SC, SE, HA
Shasta Daisy Leucanthemun x superbum N, SW, SC, SE, HA
Silver Mound Artimisia schmidtiana N, SW, SC, SE, HA
Stoke’s Aster Stokesia laevis N, SW, SC, SE, HA
Sundrops (Evening Primrose) Oenothera fruticosa SW, SC, SE
Veronica Veronica spp. N, SW, SC, SE
Yarrow Achillea spp. 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.


Sundrops

Fall blooming sundrops or evening primrose

Late-Blooming Perennials

These are plants that bloom in late summer, continuing into fall, many blooming through the earliest frost events. The time period for bloom will typically be August, September, and in warm regions continuing into October.

Common Name Scientific Name Regional Adaptation
Aster Aster spp. N, SW, SC, SE, HA
Chrysanthemum Deudranthuna x grandiflora N, SW, SC, SE, HA
Coreopsis Coreopsis spp. N, SW, SC, SE, HA
Deadnettle Lamium maculatum N, SW, SC, SE, HA
Globe Thistle Echinops ritro N, SW, SC, SE, HA
Gloriosa Daisy Rudbeckia x hybrida N, SW, SC, SE, HA
Leadwort (Plumbago) Cerastostigma plumbagonoides N, SW, SC, SE, HA
Lavendar Lavandula angustifolia SW, SC
Mullein Verbascum spp. SW, SC, SE
Obedient Plant Physostegia virginiana N, SW, SC, SE, HA
Orange Coneflower Rudbeckia fulgida var. sullivantii N, SW, SC, SE
Phlox, Tall Phlox spp. N, SW, SC, SE, HA
Pincushion Flower Scabiosa caucasica N, SW, SC, SE, HA
Purple Coneflower Echinacea purpurea N, SW, SC, SE, HA
Red Hot Poker Kniphofia uvaria SW, SC
Russian Sage Perovskia atriplicifolia SW, SC
Sneezeweed (Helen’s Flower) Helenium autumnale N, SW, SC, SE, HA
Stonecrop Sedum spp. N, SW, SC, SE, HA
Sundrops (Evening Primrose) Oenothera fruticosa 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 17, 2012
Aug 162012
 

During the spring in April to mid May when temperatures are still cool, most cool-season lawns in Idaho will use about one inch of water each week. From about late May to mid August, lawns will use about 2 inches of water per week or slightly more. Then, from mid August to late September they use just over one inch of water. During periods when significant amounts of precipitation is received, lawn sprinklers systems should be turned off. There is no need to irrigate when the soil is already filled to capacity.

Depending on the year and the onset of winter, grasses will still use close to an inch per week in October, and it is important to keep the soil moist, not overly wet, but moist going into winter. This will help prevent winter desiccation damage.

Lawns with significant shade and wind protection will not need as much water, but remember that the grass will be competing with tree roots for water and nutrients, so extra attention needs to be given to these landscapes.

 August 16, 2012
Aug 162012
 

To understand the timing of lawn fertilization, it is important to understand the seasonal growth pattern of a grass plant. In the spring, grasses are coming out of winter dormancy and begin rapid growth using stored energy reserves from last year. Grasses that are over-fertilized with nitrogen in the spring will spend too much of those energy reserves on leaf growth and will not have enough left over to take them through summer’s heat and drought stress. All that is needed in the spring is to supply the grass with just enough nitrogen fertilizer to prevent it from becoming chlorotic (very light green to yellow in color).

As temperatures rise in the summer, leaf and root growth start to slow. Over-fertilization at this time could be very detrimental to the health of the grass and even cause areas to die. Avoid fertilizing during the summer except to prevent chlorosis. Very light applications and use of a slo- release fertilizer will help keep the grass green in the summer without burning or damaging the lawn.

As temperatures cool and hours of light per day diminishes in late summer to early fall, grasses begin preparing for winter by sending their energy reserves to their rhizomes and roots. A fertilizer application at this time will help the plant maximize energy production and most of the engergy will be sent to storage instead of being used for leaf growth.

Table 1 gives recommendations for various grasses at various times of the year. Keep in mind that the March application may be omitted if green-up is satisfactory and a late fall application was made the previous year. In this case, a single application of 1 lb N per 1000 ft2 can be made. Use slow release fertilizers for a late fall application and on sandy soils throughout the year to reduce nitrogen leaching. Additionally, if you are using a mulching mower or otherwise returning clippings to the lawn, you may be able to cut back the nitrogen by about one fourth.

Table 1. Nitrogen fertilization schedule for home lawns.  (Adapted from Colorado State University lawn fertilization extension fact sheet).

Grass Type¹ & Maintenance Level² Mid March – Mid April Early May – Early June July – Early August Mid August – Mid September Early October – Early November
Rates are in lbs of N per 1000 ft2
KBG – Low 1/2 1/2 none 1 1 (optional)
KBG – Med – High 1/2 – 1 1 none 1 1 – 2 (2 is optional)
Tall fescue – Low 1/2 1/2 none 1 1 (optional)
Tall fescue – Med – High 1/2 1 none 1 1 (optional)
Fine fescue – Low 1/2 1/2 none 1/2 none
Fine fescue – Med 1/2 1 none 1 none
Buffalograss none 1/2 – 1 1/2 – 1 none none
¹Grass Type: KBG = Kentucky bluegrass
²Maintenance Level: Low = low maintenance, Med = medium, High = high maintenance
 August 16, 2012
Aug 132012
 

Selecting the proper time to prune is important. Heavy pruning at the wrong time of year can stimulate unwanted growth or prevent flowering or fruiting. Before pruning, consider time of year, type of plant and flowering periods of certain plants. See the table below.


Time of Year to Prune Various Types of Plants.
Season
Type of plant Fall Winter Spring Summer Comments
Early Late Early Late Early Late Early Late
Deciduous shrubs for shrubs
that flower before
June 1
Deciduous shrubs for shrubs
that flower after
May 30
Deciduous
trees
a
Conifers –
Shrubs and
Trees
All conifers
except for pines
(see below)
a
Pines
a
Broadleaf
evergreen
shrubs
For shrubs grown
for flowers
Broad leaf
evergreen
shrubs
For shrubs grown for foliage (hedge)

When to Prune New Growth on Pines

Pines have buds only at the tip of the branches. If a branch is pruned after a growth flush and the terminal bud is removed, regrowth is impossible. Pine branches should be pruned or pinched in early summer when the new branch (candle) has begun to elongate but before the needle bundles open. This pruning causes the growth to be more compact but still allows buds to form for the following year.

 August 13, 2012
Aug 092012
 

When we consider pruning, we naturally think of early spring. This is appropriate for the most part, because removal of branches on a plant is best done after winter cold has abated and before the plants leaf out. This helps prevents excessive weeping (sap flow from the wound) and allows time for wounds to heal during the summer months. However, there are practical reasons for completing some minor pruning during the summer.

Pruning may be needed to remove damaged or diseased branches that were not apparent during the spring. There may also be a need to remove branches with winter injury, something that does not become visible until warm weather arrives. For some shrubs, pruning may also be needed to remove spent flowers to encourage the growth of new blossoms. Fruit trees can be pruned to remove some fruit in years that fruit set is excessively high. This will result in larger fruit and help prevent alternate bearing, the tendency for fruit trees to grow fruit only in every other year.

Summer pruning

One of the main reasons to prune shrubs and trees in the summer is to control size. When pruning is done only in the spring, trees and shrubs tend to sucker where old branches are removed. These new branches grow rapidly and if left in place result in overall increased size. Removal of these new branches during the summer helps a tree or shrub to remain small in stature and more compact in shape. It will also decrease the amount of pruning needed during the next spring.

Even conifer trees can by pruned to control size. This is done by clipping off most of the “candle”, the new sprout of soft growth that emerges in the spring. This will help keep a potentially large tree small, while at the same time helping to thicken the new growth. When pruning evergreens, it is important not to remove all of the new growth (except occasionally). This will leave only older wood that will eventually lose its needles and become unattractive.

Pruning for size control with shrubs may take the form of shearing, something we do to manage the size and shape of hedges and specimen plants in the yard. Shearing not only removes lanky, tall growth, but causes the plant to branch out and become thicker.

So, don’t be afraid to break out the pruning tools in July. Selective summer pruning will improve the look of your yard.

 August 9, 2012