Bulbs can be classified as spring flowering bulbs or summer flowering bulbs. Another way to classify bulbs for use in Illinois would be hardy spring flowering bulbs and tender summer flowering bulbs.
Summer flowering bulbs (tender bulbs) are killed by cold temperatures. They must be planted in the spring when there is no longer a chance of ground frost. They need to be dug in the fall following the first frost that discolors the foliage and stored over the winter.
The spring flowering bulbs (hardy bulbs) such as tulips, daffodils and crocus need a cold period during the winter to flower. These bulbs are planted and develop a root system in the fall and bloom during the spring. Temperatures are cold enough in Illinois during the winter to meet these cooling requirements. For instance, tulips require 12 or more weeks of cold temperatures. If spring bulbs are used for forcing indoors, be sure they have been pre-cooled or they will not bloom.
By raising both spring flowering and summer flowering bulbs, the blooming season can be extended. Spring flowering bulbs normally start blooming in February with snowdrops and end in June with the alliums. The summer bulbs extend the bloom period from July into the fall season. The great variety of bloom color, flowering time, plant height and shape makes bulbs a good addition to any landscape or garden.
It is important to select good quality bulbs for planting. Factors to consider are size and firmness. Larger bulbs produce larger blooms. Select bulbs that are firm and free from soft or rotting spots or other signs of disease.
There are basically three sources for obtaining bulbs: mail order businesses, local nurseries and discount businesses. Normally, there is a larger selection of bulb varieties through mail order catalogs. The disadvantage of mail order is that the buyer does not know what the bulb will look like until received. Therefore always buy from companies that have good reputations and that you or your friends have used in the past with good results.
Once bulbs are obtained either locally or from a mail order source, they should be planted as soon as possible. If the bulbs cannot be planted immediately, keep the bulbs cool until they are planted. The preplanting storage temperature should be between 50F and 60F. Keep the bulbs away from ripening fruits which may produce ethylene and cause flowering disorders, especially with tulips.
Properly preparing the soil for bulb planting is important. Good soil drainage is essential in raising bulbs. If you have a soil with a high clay content, it can be improved by adding compost, peat moss or some other source of organic material. The organic material should be worked in the top twelve inches of soil (eighteen inches is even better).
Both spring and summer bulbs need phosphorous to encourage root development. Keep in mind that phosphorous moves very little once applied to the soil. Some bulbs are planted 6 to 8 inches deep. The phosphorus needs to be mixed in the soil below where the bulbs will be located so it can be utilized by the bulb roots. Mix bonemeal or superphosphate with the soil in the lower part of the planting bed as it is being prepared.
If bulbs are going to be maintained in a planting bed more than one year, it is important to supply additional fertilizer. Spring flowering bulbs should have mixed into the soil in the fall five tablespoons of 10-10-10 soluble fertilizer (or equivalent bulbfertilizer) plus two cups of bonemeal per ten square foot area. As soon as the shoots break through the ground in the spring, repeat the above soluble fertilizer application. Do not fertilize spring flowering bulbs after they have started flowering. This tends to encourage the development of bulb rots and sometimes shortens the life of the flowers.
Summer and fall flowering bulbs should be fertilized monthly from shoot emergence until the plants reach full flower. Apply seven tablespoons of 10 10 10 soluble fertilizer (or equivalent bulb fertilizer) split over two or three applications over ten square foot area.
The optimum pH range for bulbs is 6 to 7. A soil test of the planting area is necessary to determine if lime needs to be applied to adjust the soil pH. If needed, limestone should be worked into the soil. For good bud development, work bonemeal into the soil at planting.
Before selecting the location to plant bulbs in the landscape, consider the light requirements of the plant. Does the plant require full sunshine, partial shade or full shade? Since early spring bulbs bloom before most trees or shrubs leaf out, they can successfully be planted under trees and shrubs. Many summer blooming bulbs require full sun or partial shade.
Spring bulbs planted on a south slope will bloom earlier than the same bulbs planted on a north slope. Spring bulbs planted on a hillside will bloom earlier than bulbs planted in a valley. Cold air is heavier than warm air and behaves like water. It flows down the slope, settling in the low areas.
The general rule of thumb for planting spring bulbs is to plant two to three times as deep as the bulb is tall. This means most large bulbs like tulips or daffodils will be planted about 8 inches deep while smaller bulbs will be planted 3-4 inches deep. Planting depth is measured from the bottom of the bulb. This rule of thumb on planting depth does not apply to summer bulbs which have varied planting requirements. For planting depth of summer bulbs, consult the information supplied with the bulbs.
Tulips, daffodils and hyacinths should be planted with the nose of the bulb upward and the root plate downward. The best method of planting is to dig and loosen the entire bed to the proper depth. Press the bulbs into the soil in the planting area and cover with soil. Because the soil in a spaded bed is better drained and prepared, the planting will last longer. This method of planting is preferred over trying to plant bulbs one by one with a bulb planter. In many soils bulb planters do not work well, if at all.
Water the bulbs following planting. This will help settle the soil in the planting bed plus provide needed moisture for the bulbs to start rooting. Fall planted bulbs must root before cold weather. Avoid over-watering at planting time since this can result in bulb rot.
For both spring and summer bulbs, start watering when the flower buds first appear on the plant if the soil is dry. Shallow watering will not do the job. Remember that the bulbs may have been planted 6 to 8 inches deep and the water needs to soak to that depth. Through the bud, bloom and early foliage stage, add about one inch of water per week if this amount has not been supplied from rainfall. Water with a soaker hose to keep water off the bloom. Bulbs like alliums, such as Molly, or the shallow planted bulbs, will rot quickly if over- watered in the heat of summer.
One of the visual problems with spring bulbs is the foliage that remains after bloom. The foliage can become unsightly if the bulbs are planted in a public area of the landscape. Foliage should not be mowed off until it turns yellow and dies back naturally.
The foliage on the smaller bulbs such as snow-drops and squill will die back rapidly and cause little problem. The foliage on the larger bulbs like tulips and daffodils will take several weeks to die back. Keep in mind that after flowering, the plant needs the green leaves to manufacture food (photosynthesis) which is stored in the bulb for next year's growth. If the homeowner mows off the foliage early, the plant can no longer manufacture nutrient reserves for next year. This results in a small, weak bulb which will gradually decline and die out.
There are several ways to divert attention from the yellowing bulb foliage. Interplant the bulbs in the spring using one or two colors of annuals. Place bulbs behind the plants on the front edge of a border planting. Plant taller flowering bulbs behind lower growing foreground shrubs. Plant bulbs with groundcovers and perennials like hosta or daylilies.
Spring bulbs can be laid down to allow developingfoliage of perennials like hosta or daylilies.
The bulb bed should be covered with two or three inches of mulch. Mulch will help minimize temperature fluctuation and maintain an optimal moisture level in the planting bed. The small, early blooming bulbs should not be mulched.
Once the foliage dies back or matures in the late spring or early summer, the bulb is dormant. Summer is the dormant period for spring bulbs. As the foliage dies back, the roots that nourish the bulb also die back. With fall rains, the bulb comes out of summer dormancy and roots begin to grow again to provide the bulb nutrients and moisture.
Once the spring bulbs enter dormancy, the time is right to dig the bulbs if needed. Some bulbs benefit from digging to divide the bulbs and spread them out over the bed.
If the choice is to dig bulbs, they should be stored in a well ventilated place and replanted in the fall. Every five years daffodils and crocus should be dug and replanted to prevent overcrowding. The first sign of overcrowding will be a decrease in the flower size, uneven bloom and uneven plant height. When this occurs, dig, spread bulbs out, and replant immediately.
Leave the soil on achimenes, begonia, canna,caladium, dahlia, and ismene bulbs. Store these bulbs in clumps on a slightly moistened layer of peat moss or sawdust in a cool place. Wash and separate them just before planting.
Spread the washed bulbs in a shaded place to dry. When dry, store them away from sunlight in a cool, dry basement, cellar, garage, or shed at 60 to 65 F. Avoid temperatures below 50 or above 70 F. unless different instructions are given for a particular bulb.
Inspect your bulbs for signs of disease. Keep only large, healthy bulbs that are firm and free of spots. Discard undersized bulbs.
If you have only a few bulbs, you can keep them in paper bags hung by strings from the ceiling or wall. Store large numbers of bulbs on trays with screen bottoms. Separate your bulbs by species or variety before storing them.
Be sure that air can circulate around your stored bulbs. Never store bulbs more than two or three layers deep. Deep piles of bulbs generate heat and decay.
Most flowering bulbs are best stored over a long period at temperatures between 60F. and 68F. Try to keep the humidity in the storage area as low as possible. Never store bulbs in an area where ethylene gas produced by fruit is present. Bulbs can be stored in a container with peat moss, sand, perlite or vermiculite. Another common storage method is to place the bulbs in a very loose knit sack and hang in a sheltered, cool area. Do not divide or separate bulbs before storing them.