There are several garden tasks to do when the garden season transitions from the heat of summer to the bright colors and crisp air of autumn. The fall months are a great time to select and plant spring-flowering bulbs for next year. Spring-flowering bulbs offer reliable color and fragrance to the garden before many other plants wake from their long winter's nap. Gardeners can choose from traditional spring-flowering bulbs, such as daffodils, tulips, and hyacinths, or the unusual like squill, crown imperial, giant onion, or guinea-hen. A small investment of time and money in fall will reward you with beautiful flowers next spring.
Selecting the Right Species
There are several species and varieties of bulbs and bulb-like structures like corms and tubers that grow well in Iowa. Some of these species are readily available from retailers and others may have to be purchased from specialty producers or online retailers.
Spring Flowering Bulbs - Large Species
- tulips (Tulipa)
- daffodil (Narcissus)
- hyacinth (Hyacinthus)
- ornamental onion (Allium)
- camass (Camassia)
- crown imperial (Fritillaria imperialis)
Spring Flowering Bulbs - Small Species
- crocus (Crocus)
- snowdrop (Galanthus)
- winter aconite (Eranthis hyemalis)
- squill (Scilla)
- trout lily (Erythronium)
- species-type tulips (Tulipa)
- reticulated iris (Iris reticulata)
- grape hyacinth (Muscari)
- checkered lily (Fritillaria meleagris)
- Spanish bluebells (Hyacinthoides)
- snowflake (Leucojum)
- striped squill (Pushkinia scilloides)
- windflower (Anemone blanda)
- trillium (Trillium)
- shooting star (Dodecatheon)
- star-of-Bethlehem (Ornithogalum umbellatum)
- spring beauty (Claytonia)
- Chinese ground orchid (Bletilla striata)
- glory-of-the-snow (Chionodoxa)
Selecting High-Quality Bulbs
After deciding which types of flowers you want in the spring, select only firm, solid bulbs for planting. Avoid bulbs that are shriveled or lightweight. Bulbs that are discolored by mold or that contain soft spots should also be avoided.
Size matters when selecting bulbs. The bigger the bulb the better the flower display. Smaller bulbs often bloom but you get more bang for your buck with the larger bulbs.
Spring-flowering bulbs can be purchased as early as late August. Often for the best selection, you have to shop early! Spring-flowering bulbs purchased in late summer should be stored in a cool, dry place (such as a garage or basement) until they can be planted in fall.
Most bulbs should be planted in a full or part-sun location. Early blooming bulbs are often successful beneath a high-branched deciduous tree because they usually flower before the tree fully leafs out. After the bulbs have finished flowering, many can tolerate the light shade from trees.
Nearly all bulbs require well-drained soils. Poorly drained or wet soils often cause decline and rot, making them short-lived in the garden. Amend poor soils before planting by incorporating organic matter, such as compost or peat.
Planting Arrangement & Companion Plants
Plant spring-flowering bulbs in clusters or groups to achieve the greatest visual impact in the garden. When planting large bulbs, such as daffodils or tulips, plant at least five or more bulbs of the same variety in an area. Often groupings of 10 or more look the best. Smaller growing plants, such as grape hyacinths and crocuses, should be planted in drifts of at least 25 bulbs and looks best in groupings of 50 or more bulbs. Bulbs planted alone or in rows do not look as good in the garden as large sweeps or drifts of color. For a naturalized look, simply toss handfuls of bulbs in the garden and plant them where they land.
Consider planting them with ornamental grasses, hosta, daylily, and other perennials that will grow up later in the season and hide the foliage of the bulbs as it yellows. Select a location where their early blooms can be seen and appreciated such as along commonly used walkways or near the front door. Bulbs with different bloom times can be mixed together for a long-lasting display.
When to Plant Bulbs
October is the ideal time to plant spring-flowering bulbs in Iowa. This allows bulbs to establish and develop good roots before winter. Planting bulbs too early in the season in September when soil temperatures have not yet cooled may cause some bulbs like tulips to emerge in the fall. Procrastinators can plant spring-flowering bulbs as late as December if the ground remains unfrozen.
Plant bulbs at a depth equal to two or three times their maximum bulb diameter. Larger bulbs like tulips, daffodils, and hyacinths are often planted 6-8 inches deep. The smaller bulbs like squill, snowdrops, and crocus are often planted 3 to 4 inches deep. Larger bulbs can be spaced 4-6 inches apart while a 2-3 inch spacing is more suitable for the smaller bulbs.
Planting Depth of Select Bulb Species
|Allium spp. (Ornamental Onion) - large bulbs (A. giganteum and others)||6 inches||12 to 18 inches|
|Allium spp. (Ornamental Onion) - small bulbs (A. moly, A. unifolium, etc.)||3 to 5 inches||6 to 8 inches|
|Camassia spp. (Quamash)||4 inches||4 inches|
|Chionodoxa luciliae (Glory-of-the-Snow)||3 to 4 inches||3 inches|
|Crocus spp. (Crocus)||3 to 4 inches||3 inches|
|Fritillaria spp. (Fritillaria) - large bulbs (F. imperialis - Crown Imperial, etc.)||6 to 8 inches||12 to 18 inches|
|Fritillaria spp. (Fritillaria) - small bulbs (F. meleagris - Checkered Lily, Guinea hen, etc.)||3 to 4 inches||4 inches|
|Galanthus nivalis (Common Snowdrop)||3 to 4 inches||3 inches|
|Hyacinthoides hispanica (Spanish Bluebell)||4 inches||4 to 6 inches|
|Hyacinthus orientalis (Hyacinth)||6 inches||6 to 8 inches|
|Leucojum vernum (Spring Snowflake)||3 to 4 inches||3 to 4 inches|
|Muscari armeniacum (Grape Hyacinth)||3 to 4 inches||3 to 4 inches|
|Narcissus spp. (Daffodil) - Trumpet, large-cupped, etc.||6 to 8 inches||6 to 8 inches|
|Narcissus spp. (Daffodil) - Miniature and other small bulbs||3 to 5 inches||4 to 6 inches|
|Puschkinia scilloides (Striped Squill)||3 to 4 inches||3 inches|
|Scilla siberica (Siberian Squill)||3 to 4 inches||3 inches|
|Tulipa spp. (Tulip) - Darwin hybrid tulips, triumph tulips, etc.||6 to 8 inches||4 to 6 inches|
|Tulipa spp. (Tulip) - species or botanical tulips||3 to 5 inches||3 to 4 inches|
* Planting depth is measured from the base of the bulb to the soil surface.
Set bulbs in the ground with the pointed end up. For some bulbs or bulb-like structures, it can be difficult to tell which end goes up. If no roots or buds are apparent, you can plant some bulbs on their sides. The bulb will find the sun and bloom normally with only a little extra effort.
Planting Techniques and Tools
Bulb planters, trowels, and auger attachments for electric drills are available to assist the gardener in bulb planting. For a mass planting of bulbs, remove the soil in the entire planting area to the proper depth with a shovel. Place the bulbs in the desired arrangement or pattern and then carefully backfill the entire area with soil.
Fertilizer & Water
While not typically necessary, fertilizers can be used at planting. These fertilizers are more important for the development of next year's bulb than they are for the upcoming spring flowers. If using fertilizers, apply inorganic fertilizers, such as a 5-10-5, at the rate of 2 to 3 pounds per 100 square feet and work it thoroughly and deeply into the soil before planting. A good organic fertilizer for bulbs is bonemeal with its high phosphorus content. Apply 3 to 4 pounds of bonemeal per 100 square feet of area. Bone meal is often slower acting and more expensive than the other fertilizers. If planting clumps of bulbs, work 1 tablespoon of bonemeal into the bottom of the planting hole.
Water the areas after planting to help settle the soil around the bulbs and provide plenty of moisture for root growth, especially if soils are dry. Avoid overwatering as most bulbs do not tolerate wet conditions well.
Dealing with Early Emerging Foliage or Flower Buds
Tulips, daffodils, and other spring-flowering bulbs normally begin emerging from the ground in March or early April in Iowa. However, mild winter weather can encourage premature growth. The early emergence of spring-flowering bulb foliage is most often seen on the south and west sides of homes and other buildings. These areas are usually warmer than the rest of the yard because sunlight is reflected off the building to the ground. In addition, heated basements keep the soil near homes relatively warm.
While the premature emergence of spring-flowering bulb foliage is undesirable, the danger is not as great as it may seem. The foliage of tulips, daffodils, and other spring bulbs can tolerate cold temperatures. Often normal winter weather (cold temperatures and snow) returns, delaying further growth. A blanket of snow is especially helpful. The snow discourages additional growth and also protects the foliage from extreme cold.
Protecting Flowers from Rabbits, Deer, and Other Animals
Some spring-blooming bulbs are highly desirable to rabbits, deer, chipmunks, voles, mice, gophers, and other animals. This is especially true for tulips and crocus. These animals can dig and eat newly planted bulbs in the fall and can eat the foliage and emerging flower buds right down to the ground in spring. The best way to stop animals from eating spring-blooming bulbs is to exclude them. To prevent digging roll hardware cloth or chicken wire across the soil surface after planting and pin it down with landscape staples or bricks. Remove the fencing as soon as the foliage emerges in spring. Once the foliage emerges from the ground, place chicken wire or hardware cloth fencing around the plants. To improve the appearance the fencing can usually be removed just as blooming starts as by that point the flowers are large enough to not be bothered by rabbits and other rodents.
Repellents that rely on strong scents or unpleasant tastes can discourage wildlife pests from coming into an area or browsing on bulbs to prevent further damage. However, repellents are typically not very effective at preventing damage. There are two types of repellents - taste and area. Taste repellents like pepper, garlic, or peppermint have a foul taste that prevents extensive browsing (although some browsing will occur before the deer or other animal realizes it tastes bad!). Area repellents such as coyote urine, rotten eggs, and garlic, rely on smell and are typically applied to the perimeter of the area to keep animals from entering the garden space.
Repellents must be reapplied often, especially after rain events. The label directions will help determine the frequency of necessary applications. Treat those areas that have been affected as well as areas nearby to prevent further damage. While repellents may not be very effective, they can be used in conjunction with other management options to further help prevent damage.
Unplanted tulip and other spring-flowering bulbs oftentimes shrivel up and die over winter. Tulip bulbs that remain viable (alive) until spring usually don’t perform well when planted in spring. Spring-flowering bulbs are planted in fall so the bulbs have adequate time to develop good root systems before winter. Additionally, they must be exposed to cold temperatures in order to bloom. Spring-planted bulbs usually don’t grow well because they lack well-developed root systems. Plus, they often fail to bloom. Regrettably, it’s usually best to discard unplanted tulip bulbs in spring. Buy and plant additional bulbs in the fall.
Saving Forced Spring-Bulbs
Tulips, hyacinths, and most other spring-flowering bulbs that have been forced indoors are usually discarded after flowering. Most won’t bloom again when planted outdoors. Daffodils are an exception. Daffodils are more vigorous than tulips and most other spring-flowering bulbs. Forced daffodils can be saved and successfully planted outdoors.
The care after flowering is important if attempting to save forced bulbs. After blooming, remove the spent flowers and place the plants in a sunny window. Water regularly until the foliage begins to yellow. At this point, gradually cut back on watering until the foliage withers and dies. Carefully remove the bulbs from the potting soil, allow them to dry for one to two weeks, then store the bulbs in a cool, dry location. Plant the bulbs in the fall.
- Forcing Flower Bulbs
- Suggested Daffodil Cultivars for Iowa
- Early Spring Blooming Perennials
- How to Overwinter Tender Perennials
- Growing and Overwintering Tender Perennials
Updated from an article that originally appeared in the September 17, 1999 issue of Horticulture and Home Pest News, p. 119.