By Judy Ferring PC EMG
Warning: there’s temptation lurking at your local garden supply store. It’s in the form of bulbs you can plant this spring – lilies (asiatic, oriental, cana and calla); crocosmia; dahlias; gladiolas; caladiums; elephant ears; and several types of iris.
There are a lot of good reasons not to resist. These bulbs, most to be planted in May, will put on a colorful show after the first blush of spring and early summer has faded. There are at least two reasons why they are good replacements for some of your budget for annual flower seeds.
First, they’re larger than seeds, easier to handle and easier to spot once they’ve sprouted.
Second, because they can be used year after year, with some simple husbandry, they’re a good long-term investment. Traditionally, summer bulbs have been dug up and stored indoors for the winter. But if you’re judicious in matching your selection of bulb and planting site, some can stay in the ground over the winter.
“There are SO many choices, as long as the bulbs are able to sleep in a dry bed during the winter,” says Becky Heath, president and CEO of Brent and Becky’s Bulbs, based in Gloucester, Va. “In my raised beds (most of which are built above ground, which normally makes it feel colder because the bulbs are not surrounded by the earth), dahlias over-winter better than when they are planted in the ground because the drainage is better. Winter hardiness is important but there are other factors, too.”
Warmth is an important factor, provided by a sunny location and a thick layer of soil and mulch. Good drainage preserves that warmth from ice damage. Those that bloom late into the fall have the added advantage of having stored large amounts of nutrients in their geophyte systems.
Which brings up another warning, if you buy bulbs online or in a catalog. When you open the package, it may not look like a bulb at all. Stay calm. All bulbs are geophytes – that is, an herbaceous plant that relies on an underground storage organ rather than a fibrous root system for nutrients. Besides bulbs, geophytes come in the form of corms, tubers, tuberous roots and rhizomes.
The real secret for in-ground wintering these geophytes, according to a bulletin for commercial flower growers from the Virginia Extension Service, is to plant them deep in the spring (May or June) and mulch them heavily in the fall. Bulbs that are hardy in zones 7-10 can be hardy to zone 6 or even 5 “if they go through winter under a 12-inch layer of leaves or a 6-inch layer of shredded bark,” writes Andy Hankins, extension specialist at Virginia State University.
Springtime roadsides throughout Patrick County prove the winter hardiness of various iris. Deep planting won’t do for these but a thick layer of mulch that’s removed in the spring could be helpful. Likewise for Kniphofia: zoned 5b-9, they fill many Patrick County roadsides in the spring.
Many gardeners in Patrick County have found dahlia-friendly micro-climates for successful over-wintering. The odds are in your favor since this huge family of diverse flowers are usually rated for zone 7 as their northern-most hardiness zone. “Top sized tuberous root clusters (of dahlias) have overwintered in our whz7 (winter hardy zone 7) gardens with extra winter mulch and excellent drainage among our daffodils and tulips,” reports Heath.
Similar to dahlias, gladiolas prefer full sun and well-drained soil, and many are being marketed as winter hardy. “The accepted hardiness zone for the classic Grandiflora gladioli is zone 8, but it’s well known that by covering them with a good mulch, you can keep them alive in zones 6 and 7,” writes gardening blogger Larry Hodgson.
For this, he stipulates “the best possible growing conditions”: full sun, well-drained soil, extra deep planting (6 inches rather than the usually recommended 2-4 inches; 6-8 inches of well-aerated fall mulch plus a good layer of snow. “Under those conditions, I find that I can grow glads outdoors with reasonable success in my USDA zone 3 … and that’s really cold!”
Some varieties are hardier than others. “To start with, dwarf gladiolas (often sold under the name nanus, although in fact there is no such species) ) are well known to be hardier than the usual Grandiflora hybrids and can be safely grown in zone 6 without protection. With a good mulch, they’re pretty much certain to thrive in zones 4 and 5,” says Hodgson.
Species varieties are the best candidates for over-wintering, agrees Heath. As illustrated in her company’s catalog, “dwarf” doesn’t seem particularly short: nanus ‘Halley’ can grow to 18 inches tall, tubergenii ‘Charm’ to 36 inches. Best-priced test might be her species mixture of 50 bulbs for $27.
There’s little doubt that lily of the valley (formal name Convallaria) will over-winter. Rated for growing zones 3-8, some gardeners consider it invasive. Like most of the over-winter candidates, it wants well-drained soil but unlike others that demand full sun, lily of the valley prefers shade. Most are white; at least one species is pink. All are heavily fragrant. For all its hardiness, they can be a slow starter and will often take a season to establish itself.
There’s even a begonia that’s a candidate for over-wintering. On the whole, these heat tolerant shade lovers are treated as annuals but a few can be left outside under the right conditions. Case in point: Begoniaceae boliviensis “Bertini,” which sports reddish orange blossoms and dark green serrated leaves. Rated whz 7, it has wintered over in a protected well drained spot, according to Heath.
On Feb. 23, summer-blooming bulbs will be discussed by Ursula Allen and John Morehead, on the Patrick County Master Gardeners (PCMG) monthly program on WHEO radio (92.7 FM and 1270 AM).