Longing for a lavender plant?

Chicago Botanic Garden has tested a few for cold-weather hardiness

The deep freeze of early winter has left my lavender plant truly bedraggled. The slender gray leaves are drooping, and some of the lower ones are black.

It’s a reminder that lavenders have a difficult life, but with some luck and a modicum of care, they will last a few years and do the trick. The trick? Transporting you to Grandma’s garden or the French Riviera, or wherever the sight of those purple flower spikes and their memory-charged fragrance will take you.

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.

Find a sunny spot with freedraining 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.

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. Twentyfour of the 40 made it through four winters, which is impressive; in 2014, the mercury dropped to 16 degrees below zero.

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, said Richard Hawke, the plant evaluation manager,.

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.