My current frozen specimen seems to be crying for help, except that with a winter-bashed lavender, the best course is to do nothing.
This is a type of intervention because the impulse is to chop back the forlorn lavender in late winter in advance of spring growth. Lavender doesn’t behave like other perennials; it thinks it’s a woody shrub, and a hard pruning will finish it off.
The key is to wait until late April or early May to see what grows back. Whatever tidying you do then, don’t cut below the new growth.
There are other quick ways to kill lavender. One is to stick the plant in wet clay soil. The other is to give it a thick wood mulch.
If my lavender dies, I have an ingenious backup plan: I’ll plant another. Every garden should have one.
Find a sunny spot with free-draining soil. You can create the latter condition with a raised bed. I incorporate pea gravel and some lime into my lavender beds and then mulch with another layer of gravel. Chicken grit would work, too, if you can find it. This soil work minimizes wet roots in summer and a wet crown in winter, both of which are lethal.
I am thinking about lavender not just because of my bedraggled plant but because the Chicago Botanic Garden recently released the results of an evaluation of lavender varieties. Quite separately, another botanical garden, Mount Cuba Center, in Hockessin, Del., published the results of its own multiyear trials of phlox.
Phlox is native and lavender is not, but they share much in common: They are old-fashioned summer perennials that deserve a revival. Fragrant and colorful, they are also magnets for bees, butterflies and other pollinators.
First the lavender.
The Chicago gardeners tested 40 varieties over seven growing seasons. Some barely got out of the starting gate before dying, while others grew to maturity. The principal test for a lavender in Illinois is its winter hardiness. Twenty-four of the 40 made it through four winters, which is impressive; in 2014, the mercury dropped to 16 degrees below zero. Hardiness isn’t as much a concern in the Mid-Atlantic, but as this winter has shown (or will show come spring), it’s still an issue for the lavender grower to deal with.
Richard Hawke, the plant evaluation manager, said the trial debunked the idea that Chicago was too cold for lavender. There are two key lessons from the trial. Picking the correct variety is critical to success. For example, although Hidcote and Munstead are considered ornamental twins, as silver-leafed compact English lavenders, “Munstead was much better than Hidcote” in winter survival, Hawke said.
The other takeaway: Soil preparation is vital. Hawke’s team planted the varieties in raised beds, but in clay-based soil. “If we had a free-draining soil that was more sandy loam, we would have seen more survive,” he said.
But the trial lavenders were also rated for their ornamental characteristics, including flower production, pleasing shape and general health. The evaluators found that there were 13 superior varieties that offer gardeners a range of size, habit, and leaf and flower color.
A dozen were forms of the low, broad English lavender, and only one was the larger, hybrid lavandin seen in the perfume fields of Provence.
The top three, in order, were Imperial Gem, with dark lavender blooms rising to 22 inches; Royal Velvet, a little taller and narrower, also with dark lavender blooms; and Munstead, with lavender-blue blooms. The best pink flowering variety was Jean Davis, and the most compact was SuperBlue, just 10 inches tall after four years. The superior lavandin was Phenomenal, which is more compact than others such as Provence and Grosso, both of which I’ve lost over the years.
Mount Cuba’s phlox trial focused on the tall phlox of summer, the garden phlox (Phlox paniculata), and the gardeners tested 66 varieties over three years. I love the low-growing phlox of the spring shade garden, but I stopped growing garden phlox years ago because of its susceptibility to powdery mildew. This test must force a rethinking of that, because the top performers shrugged off the fungus, though you’d still want to plant them in a sunny and open location and keep them watered.
The highest performer was a variety named Jeana, a pink bloomer whose panicles are smaller than others, which isn’t a bad thing, though it is tall, reaching five feet. Butterflies love phlox, but Jeana drew them like no others. Other top performers were Glamour Girl, a coral-pink variety that reaches three feet; Delta Snow, a four-footer with white blooms with a purple eye; and Dick Weaver, magenta pink with an abundance of smaller domed panicles.
Some of the best-rated varieties did develop a little mildew in the second and third years, said George Coombs, the trial manager, but that was a product of them not being pampered and all being grown together. They would be cleaner under optimal garden cultivation.
What is particularly valuable about garden phlox is that it blooms in the dog days of July and August, when a lot of perennials have gone on vacation. Some of the top performers are also quite fragrant, especially Dick Weaver and the varieties Robert Poore (magenta) and David (white).
Coombs said they don’t need staking, but they are among the perennials you can cut back in May, which will make them more compact and delay flowering, both desirable in my book.
The trial extended to other, lesser-known and earlier-blooming phlox species that may be hard to find but are worth the effort.
Kim is a selection of the Carolina phlox with handsome, mildew-free lime-green leaves. “However, the most impressive feature of Kim is its showstopping light pink flowers which blanket the plant from late May through early June,” Coombs wrote in the research report.
Another top performer was a variety of the smooth phlox (P. glaberrima) named N3 Springfall. It grows to 28 inches with “copious numbers of vivid, lavender-pink flowers in June.” Other varieties worth seeking out are Bill Baker, Forever Pink and Morris Berd. After blooming, you can remove the faded flower stems to leave a basal cluster of leaves that persists ornamentally through the winter.
With all these superior varieties, it’s time to get reacquainted with these reinvented classics. But heed Coombs’s admonition about seeking out named varieties. “You have to be picky what you choose.”
Tip of the Week
Test the viability of old seed by placing 10 to 20 seeds within the folds of a wet paper towel. Put the towel in a sealed plastic bag and keep it in a warm place, such as the top of a refrigerator. Light is not necessary. Check them after a week. If the germination rate is less than 50 percent, discard the seed packet.
— Adrian Higgins
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