Brighten your garden with summer bulbs

Richard Bogren, Gill, Daniel J.


For Release On Or After 05/18/12

By Dan Gill
LSU AgCenter Horticulturist

Summer-flowering bulbs provide an excellent way to introduce colorful flowers, interesting foliage and even fragrance into the summer landscape. Most summer-flowering bulbs are native to tropical or subtropical climates and will reliably bloom here for many years.

These plants serve a wide variety of uses in the landscape by providing valuable additions to flower beds, perennial borders, ground covers and containers. Think of them as long-lived herbaceous perennials that will grow where they are planted for many years.

In common usage, the term “bulb” is used for any fleshy, below-ground structure produced by a plant. This includes actual bulbs as well as tubers, corms, rhizomes and tuberous roots. Summer bulbs are those that bloom roughly from May through September. (Yes, our 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, almost always a few kinds of bulbs 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 exceptions. Full to part sun (six hours or more of direct sun each day) 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 have a dormancy period when the foliage dies off and the bulb rests. This period generally occurs in winter. Even bulbs that are normally evergreen, such as agapanthus, will go dormant if the winter is cold enough with several hard freezes.

As bulbs enter dormancy, growth stops, and the foliage will become yellow, then brown. At that time, the foliage may be trimmed back. 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 that’s 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 and reduce flowering.

When planting summer bulbs, you should generally dig in generous amounts of organic matter, such as compost, aged manure or peat moss, before you plant. A light sprinkling of a general-purpose granular fertilizer every six to eight weeks is quite sufficient for most summer bulbs during active growth beginning in March or April and ending in August.

Seed pods will sometimes 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 may also plant pre-sprouted bulbs that are available at many local nurseries. Unless you want colorful growth immediately, the unsprouted bulbs are generally a better buy. Bulbs left in the ground last year should sprout any time now, so keep an eye out for them. Caladium foliage is present from April through October and combines beautifully with impatiens, achimenes, begonias, torenias, ferns, hostas and gingers.

A number of summer bulbs are outstanding for Louisiana.

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), zephyranthes.

Bulbs for part shade to shade include Arum italicum, achimenes, alpinia, bletilla, caladium, crinum, costus, curcuma, globba, hedychium, hymenocallis, kaempferia, oxalis, walking iris (Neomarica).

Rick Bogren

5/1/2012 9:16:50 PM
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