Summer Flowering Bulbs for Louisiana Landscapes

Daniel Gill  |  5/2/2015 1:53:14 AM

It seems that when flowering bulbs are mentioned, the first thing that comes to mind are the lovely spring flowering bulbs that brighten our gardens from mid-winter through the spring – things like daffodils, tulips, snowflakes and Dutch irises.

But, we also have summer flowering bulbs. Overall they are more adapted to our climate and are more likely to establish as perennials. They also tend to bloom over a longer period. They provide an excellent way to introduce color and interest into the summer landscape. Summer bulbs are those that grow and bloom roughly from April/May through September/October.

Summer bulbs are generally grown for their attractive flowers, but a number of them are grown for their attractive foliage, including caladium, peacock ginger, purple oxalis and variegated shell ginger.

Most summer flowering bulbs are native to tropical or subtropical climates, which is why they will reliably bloom here for many years. Indeed, for some of these plants the trick is not getting them to grow, but keeping them under control. These plants fill a wide variety of uses in the landscape providing valuable additions to flowerbeds, perennial borders, ground covers and containers.

In common usage, the term “bulb” is used by gardeners for any fleshy below ground structure produced by a plant, including bulbs, tubers, corms, rhizomes and tuberous roots. Although generally not critical, it is sometimes important to know that these structures do differ significantly from one another and can influence how the plant is cultivated and propagated.

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 situation 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), elephant ears and some gingers are a few exceptions. Full to part sun (6 hours or more of direct sun a day) is important to most of these plants for healthy growth and flowering, but many, such as achimenes, caladium, gingers and walking iris, 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 the winter. Even bulbs that are normally evergreen, such as agapanthus and crinum, will go dormant if the winter is cold enough and severe freezes occur.

As bulbs enter dormancy growth stops and the foliage will become yellow, then brown. At that time, the foliage may be trimmed back to the ground. 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. This may also be done when winter cold freezes back the foliage of summer bulbs.

Avoid removing healthy, green foliage. It is the leaves which 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.

Most summer bulbs are not that fussy about care. You should generally dig generous amounts of organic matter, such as compost, aged manure or peat moss, into the area before you plant your bulbs. A light sprinkling of 15-5-10 or something similar every 6 to 8 weeks during active growth, beginning in April and ending in August, is quite sufficient for most summer bulbs.

Do be sure to keep your summer bulb plantings well mulched. Mulches are a great way to reduce weed problems. In addition, mulches conserve moisture and keep the soil cooler.

Seed pods will sometimes form after a summer bulb has bloomed. Unless you are breeding the plants or want to grow some from seeds, allowing the seed pods to develop is a waste of energy for the plant. I recommend that you remove the old flower spikes or developing seed pods as soon as you notice them.

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 of the summer bulbs is the caladium, which is grown for its colorful foliage rather than flowers. You can buy caladium tubers now and plant them directly into the garden. You may also plant pre-sprouted bulbs that are available at many local nurseries. Unless you need growth immediately, the unsprouted bulbs are a better buy. Caladium foliage is present from April through October and combines beautifully with impatiens, achimenes, begonia, torenia, ferns, hosta, and gingers.

Gingers are wonderful for area gardens and grow well in partially shaded conditions. Because they are native to the tropics, ornamental gingers thrive in our hot, humid summers. Despite their tropical origins, however, a large number of gingers are completely root hardy here and make excellent permanent additions to your landscape.

The plants we call gingers actually include many genera, with many different sizes, growth habits and shapes of flowers. Low growing gingers, such as Kaempferia and Globba, make great ground covers while larger gingers reaching 6 to 12 feet, such as Costus, Alpinia and Hedychium, can be used for accent, screens or background plantings.

This is just a taste of the many outstanding summer flowering bulbs for our area. They are generally reliable, long-lived and easy to grow. I recommend you dive in and have fun. The following lists will help you get started.

Summer bulbs for full sun to part sun: agapanthus, blackberry lily (Belamcanda), calla lily (Zantedeschia aethiopica), caladium (sun tolerant types), canna, crinum (many species and hybrids), crocosmia, dahlia (they often languish when it gets really hot), dietes, garlic chives (Allium tuberosum), gloriosa lily, rain lily (Zephyranthes and Habranthus), shell ginger (Alpinia zerumbet), spider lily (Hymenocallis ‘Tropical Giant’ ), Philippine lily (Lilium formosanum), oxalis, stargrass (Hypoxis angustifolia), Tigridia, society garlic (Tulbaghia).

Summer bulbs for part shade to shade: achimenes (especially Purple King), voodoo lilies (Amorphophallus), arisaema, caladium, calla, gingers (Costus, Curcuma, Globba, Kaempferia, Hedychium, Alpinia), walking iris (Neomarica), oxalis.

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