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AUTHOR

David Trinklein
University of Missouri
Division of Plant Sciences
(573) 882-9631
trinkleind@missouri.edu

Post-flowering Care of Spring Bulbs

David Trinklein
University of Missouri
(573) 882-9631
trinkleind@missouri.edu

Published: May 2, 2014

“The flowers of late winter and early spring occupy places in our hearts well out of proportion to their size”.

This quote from the late horticulturist Gertrude Smith Wister expresses the yearning most people have for spring, and the beauty of nature that accompanies it. Interestingly, the word “spring” to describe a season of the year first appeared in the 16th century. Before that date, the season was called “springing time,” referring to the time of the year when plants started to appear, or spring, from the ground. Undoubted, many of the plants that suddenly appeared were the spring-flowering, or Dutch, bulbs. Centuries later, we still wait anxiously each year for their colorful arrival.

Pink tulips

The beauty of spring-flowering bulbs is ephemeral; perhaps this is one reason we cherish them so. The question of what to do with the plants after they have flowered is an important one to consider, especially if we want to enjoy them again next spring. Spring-flowering bulb plants are fairly self-sufficient as long as we give them proper care during and immediately after their flowering season.

Most of the recommendations for the post-flowering care of spring-flowering bulbs are aimed at encouraging bulb enlargement. During bloom and (particularly) after bloom time, it is important to keep the foliage of spring-flowering bulbs healthy and growing. Vigorous leaves are necessary if the plant is to produce the food needed for bulb development. In order for flower buds to form in them, bulbs must hold adequate food reserves. The premature removal of leaves, or allowing them to be shaded out and weakened, can lead to few if any flowers the ensuing spring. Therefore, it is best to allow foliage to remain on the bulbs until it begins to yellow and die as the season progresses. The earliest leaves should be removed is at the yellowing stage, when leaves are no longer manufacturing food because of the lack of chlorophyll. If possible, it is best to allow them to die back naturally.

When spring-flowering bulbs are located in flower beds or borders, gardeners often tie the foliage together to make room for other herbaceous ornamentals. This practice is not recommended since, when tied together, the leaves of the plant cannot intercept the maximum amount of sunlight. This, in turn, reduces photosynthesis and the amount of food available for enlarging the bulb.

Adequate nutrition also is important for proper bulb development. As the plants flower (or immediately thereafter) fertilizer relatively high in phosphorous but low in nitrogen should be applied. Applying high amounts of nitrogen during the spring of the year can lead to root rots. A fertilizer such as 5-10-5 applied at the rate of about two pounds per 100 square feet is a good choice.

Bonemeal also is a good source of phosphorous and preferred by many for bulbs because of its slow breakdown and release of nutrients. It should be noted, however, that if digging animals are a problem in the garden, bonemeal tends to attract them. Whatever the fertilizer chosen, take care to keep it off the leaves and do not spread it too close to the base of the plants. Manure is not a good choice for feeding bulbs unless it has been very well aged.

Since the goal of post-flowering care is to direct as much of the plant’s energy as possible into enlarging the bulb, removal of flowers after they have withered is recommended. This true especially for large-flowering bulbs such as tulip, hyacinth and narcissus. In addition to improving garden appearance, flower removal will cause the plant to focus its energy on bulb enlargement instead of seed formation.

Saving seeds is hardly worth the effort as a means of propagation spring-flowering bulbs, since it normally takes three or more years to produce flowering-sized plants from seeds. Additionally, because of cross-pollination, seedlings are quite variable and often are less attractive than the parents that gave rise to them.

Transplanting spring-flowering bulbs should wait until the fall, if at all possible. If bulbs must be moved during the spring, lift the clumps with as large a volume of soil surrounding the roots as possible. Carefully reset the plants with soil intact in the new location and water well. If some foliage should be lost, it does not necessarily mean that the bulbs will die. They will, however, have been weakened and might not flower the following season. Delicate species such as tulip might not survive if their foliage is lost during the transplanting process.

Good soil drainage is one of the most if not the most important considerations when locating bulbs. Tight soils with poor drainage frequently cause stunted growth. Additionally, the excess moisture held during wet periods stresses the roots of the bulbs leaving them more susceptible to rot. Many bulbs can be grown under deciduous trees, especially if the leaf canopy of the latter is not too dense. Such is often the case with younger trees. As trees mature and the shade they cast intensifies, the lack of light as well as root competition between bulbs and the tree will result in reduced growth and poor (if any) flowering. At that time bulbs should be transplanted to a better location.

After the foliage of spring-flowering bulbs has yellowed or died-back it should be removed and discarded. Even though leaf diseases are not a major problem with bulbs, dead leaves can help spread the inoculum of diseases that might have developed.

Tulips, hyacinths, narcissus and other bulb species forced in pots for spring bloom can be planted in the garden after their foliage has died. Planting can be done in the spring, or the pot of dormant bulbs can be placed in a cool, dry location until planted outdoors in the fall.

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REVISED: September 29, 2015