Hardy bulbs exceed all other groups of plants in producing color in the spring garden. For the most part they are the earliest plants to bloom, and many have exceptionally showy flowers. The gardening season begins with the snowdrops and winter aconites, usually in early March. These are soon followed by crocuses, scillas, and chionodoxas; then come the hyacinths, daffodils, and tulips. Bulbs are also a most versatile group of plants; there is a type for any location. Attractive mass plantings can be made in solid beds, to be followed in June by annuals. Groupings can be spotted about in a perennial border or rock garden. Bulbs are attractive along paths and walks, planted around pools, or placed in front of foundation plantings around the home. Most spring bulbs, with the exception of tulips, can also be effectively naturalized.
Site
Most bulbs do well the first year regardless of where they are planted.
Very few do well for several years unless they have a fair amount of light and
generally favorable growing conditions. Planting bulbs beneath large trees is
seldom satisfactory because of the dense shade cast by the trees and the competition
with tree roots. Scilla sibirica crocus, winter aconite, and snowdrop
(Galanthus) however, give satisfactory performance under trees.
Very few of the hardy, spring-flowerings bulbs tolerate wet, soggy soil conditions during the winter. Plant them in a situation where there is good drainage and where there is no danger of water standing on the surface of the ground through the winter or spring. Camassia is an exception and does well in wet, almost swampy places. It is imperative to plant the so-called botanical or species tulips and narcissi in areas with perfect drainage, where it is dry and sunny during the summer.
Soil
Preparation
In most spring-flowering bulbs the buds are already formed at the time the
bulbs are planted in the fall. The soil must be prepared well if the bulbs are
to remain in vigorous condition for several years. Fertilizer added to the soil
before the bulbs are planted increases growth. The improvement in growth is
not evident until the second year when the bulbs that were fertilized at planting
maintain vigorous growth and large flower size, whereas those not fertilized
tend to become smaller and poorer in quality. The best fertilizer is a complete
commercial one such as 5-10-5 or 5-10-10, applied at the rate of 1 pound to
100 square feet of surface area.
Work it thoroughly into the top 4-6 inches of soil. After bulbs are established, increase fertilizer applications to 2 pounds per 100 square feet when the bulbs are in bloom. Avoid fertilizer contact with bulb foliage and scratch the fertilizer into the upper inch of soil. Organic matter can be added to "heavy" soils to improve their physical structure. It is applied at the rate of 3 bushels per 100 square feet and worked into the top 8 inches of soil. Manure can also be a source of organic matter. It should be well rotted, for fresh manure may injure the bulbs. Do not exceed 2 bushels for each 100 square feet.
Planting
In some localities where the soil is light and sandy, bulbs can be planted
by the dibble method. Make a small hole in the soil with a short-pointed stick,
place the bulb in the soil, and, after pressing the bulb down into the soil
as far as possible, cover it with soil. In heavy soils, use a trowel to dig
the hole for each bulb. The soil underneath the bulb should be loose so that
the roots can easily penetrate the soil.
Time
of Planting
October is the best month to plant all the spring-flowering bulbs. Tulips
show some reduction in size of bulb and length of stem when planted after December
1, but any time before December 15 is reasonably satisfactory for them.
Depth
of Planting
The depth at which to plant bulbs is important. The best depth to plant
tulips and narcissi is with the tops of the bulbs 5 inches below the surface
of the soil. For narcissi and daffodils, the depth of planting makes considerable
difference to the future growth of the bulb, but tulips are somewhat more tolerant
of unfavorable depths. In light sandy soils, plant tulips deeper than in heavy
soils. Plant smaller bulbs with their tops about 2 inches below the surface
of the soil. In this group are scillas, chionodoxas, grape hyacinths, snowdrops,
and any of the others that have a diameter of 1 inch or less. As a rule, the
depth of soil above the top of the bulb should be about twice the diameter of
the bulb.
Spacing
Plant the larger growing bulbs, such as tulips and daffodils, about 8 inches
apart. This gives the bulbs space for 2 or 3 years' growth before they must
be dug up and divided. Plant crocus and grape hyacinths about 4 inches apart.
Some of the smaller bulbs, such as winter aconites and scillas, should be placed
from 2 to 3 inches apart. If you make a naturalized planting, place narcissi
at least 10 inches apart and set the small bulbs about 20 to a square foot.
Grape hyacinths, scillas, chionodoxas, snowdrops, and other small bulbs are
much more effective planted in mass rather than individually.
Rodents
Precautions should be taken to prevent rodents from feeding on the bulbs.
When the bulbs are planted in beds, cover the beds with fine mesh wire to prevent
mice from digging out the bulbs. Certain repellent materials available at garden
centers, can be used. As a rule, place a small handful of the repellent around
the bulb at the time of planting.
Growth
Other practices besides planting affect the growth and development of bulbs
over a period of years. The removal of seed pods is important. When the pods
are left on tulips and narcissi, the new bulbs are much smaller than when the
pods are removed.
Removing the leaves has just the opposite effect. The more leaves removed from the bulbs when the flowers are cut, the smaller are the new bulbs produced. If the two lower leaves of tulips are left on, the new bulbs produced are practically normal in weight. Narcissi require from 4 to 6 leaves to produce normal-sized bulbs.
Let the leaves remain on the spring-flowering bulbs until they show signs of ripening and turning yellow. Tulip bulbs usually reach their full development about June 15. Narcissi complete their development about the middle of July. Other types of bulbs vary greatly in the date at which they mature. Cut off the foliage of the bulbs at the ground level when it is fully mature. Remove it from the garden and discard it.
Failure
to Bloom
Old established clumps of bulbs may not produce flowers because they are
overgrown and the bulbs have become too crowded. Correct this by digging, separating,
then resetting the bulbs. If bulbs are dug too soon after flowering, before
they mature, no flowers will develop the next season; but if the bulbs are left
in place, they will flower the second year.
Digging
After several years in the ground, both daffodils and tulips form a clump
of multiple bulbs, resulting in a gradual decline in stem length and flower
size. Daffodils grow many years before the clumps need dividing. Tulips decline
sooner and may benefit by digging the clumps and dividing the bulbs every several
years. If the bulbs have declined sharply, it may be better to discard them
and start again with new ones. Tulips rarely show as well after the first year.
In the years bulbs are to be dug, allow them to mature as long as possible. Around the last of June or the middle of July, when the foliage turns yellow, lift the bulbs carefully, free them from soil, and remove the tops. The bulbs can be divided and replanted immediately. Otherwise, wash the soil from the bulbs with a hose and then spread them out in a shady, airy place to allow the surface to dry thoroughly. Then place them in shallow boxes and store them in a cool, dry, airy place. They will be ready to plant in the fall. Grade the bulbs, for many of the smaller ones will not produce flowers the following year. Plant only the large bulbs in beds or borders. The smaller ones can be planted in rows in a nursery bed and allowed to develop. They will usually form flowering-size bulbs in 2 years.
Reprinted from: The Culture of Spring-flowering Bulbs, by R.E. Lee, Professor Emeritus and R.E. Kozlowski, Department of Floriculture and Ornamental Horticulture, Cornell University, 9/86. This publication replaces Cornell Extension Bulletin 896.
For more information contact: Tom Kowalsick, Extension Educator - Horticulture, CCE - Suffolk County
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