Daniel Gill, Merrill, Thomas A. | 4/30/2005 1:45:19 AM
Get It Growing For 5/13/05
By Dan Gill
LSU AgCenter Horticulturist
Summer-flowering bulbs are a great way to brighten up your garden, and since most of them are native to tropical or subtropical climates, they will reliably bloom here for many years.
These bulbs are an excellent way to introduce colorful flowers, interesting foliage and even fragrance into the summer landscape. The plants fill a wide variety of uses in the landscape – providing valuable additions to flower beds, perennial borders, ground covers and containers.
Basically, you can think of summer-flowering bulbs as long-lived herbaceous perennials that will grow where they are planted for many years.
In general, the term “bulb” is used for any fleshy below-ground structure produced by a plant. So that means it includes bulbs, tubers, corms, rhizomes and tuberous roots. Summer bulbs are those that bloom roughly from May through September. (Yes, Louisiana’s summer does extend through September.)
Providing general instructions on care for summer-flowering bulbs is difficult, because they are such a large and diverse group of plants. Indeed, no matter what growing conditions you have, there are almost always a few kinds of bulbs that will thrive for you.
Most summer bulbs prefer good drainage, although calla, canna, crinum, spider lily (Hymenocallis), Louisiana iris, yellow flag and some gingers are a few exceptions. Full to part sun (6 hours or more of direct sun) is important to most of these plants for healthy growth and flowering, but many, such as achimenes, caladium, gingers and bletilla, do fine in shadier spots.
Most summer bulbs also have a dormancy period when the foliage dies off and the bulb rests. This period generally occurs in the winter. Even bulbs that are normally evergreen, such as agapanthus, will go dormant if the winter is cold enough and several hard freezes occur.
As bulbs enter dormancy, growth stops, and the foliage will become yellow and then brown. At that time, the foliage may be trimmed back. But be sure to place markers where the dormant bulbs are located. Sometimes it’s hard to remember exactly where they are when nothing shows above ground, and you can accidentally dig into them with a shovel if you’re not careful.
Avoid removing healthy, green foliage. The leaves manufacture the food which is stored in the bulb. If you frequently remove healthy foliage, you will reduce the plant’s ability to create food, weaken the bulb, lower the vigor of the plant and reduce flowering.
When planting summer bulbs, you generally should dig generous amounts of organic matter, such as compost, aged manure or peat moss, into the area before you plant. A light sprinkling of a general-purpose granular fertilizer every 6 to 8 weeks during active growth – beginning in March or April and ending in August – is quite sufficient for most summer bulbs.
Seed pods sometimes will form on these plants after the flowers fade. Unless you are breeding the plants or want to grow some from seeds, remove the old flower spikes or developing seed pods as soon as you notice them. Allowing the seed pods to develop is a waste of energy for the plant, looks unattractive and may cause the plant to lean over with the weight.
Most summer bulbs are best propagated by dividing the clumps when they are dormant in early spring. Some bulbs, like crocosmia, do best divided every year or two, while others, like agapanthus, prefer to be left alone.
One of the best known and popular summer bulbs is the caladium, which is grown for its colorful foliage rather than flowers. You can buy caladium bulbs now and plant them directly into the garden. You also may plant pre-sprouted bulbs that are available at many local nurseries. Unless you need growth immediately, the unsprouted bulbs generally are a better buy.
Caladium bulbs left in the ground last year should sprout any time now, so keep an eye out for them if they’re not up already. Caladium foliage is present from April through October and combines beautifully with impatiens, achimenes begonias, torenias, ferns, hostas and gingers.
There are a number of outstanding summer bulbs for Louisiana. Summer bulbs for full sun to part sun include agapanthus, alpinia, belamcanda, canna, crinum, crocosmia, curcuma, dahlia, dietes, eucomis, garlic chives (Allium tuberosum), gladiolus, gloriosa lily, habranthus, hymenocallis, iris (bearded, Siberian), lilies (especially the Philippine lily), oxalis, tigridia, society garlic (Tulbaghia violacea) and zephyranthes. Summer bulbs for part shade to shade include Arum italicum, achimenes, alpinia, bletilla, caladium, crinum, costus, curcuma, globba, hedychium, hymenocallis, kaempferia, oxalis and walking iris (Neomarica).
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.