Herbaceous Ornamental of the Month: Jack Frost brunnera (brunnera macrophaylla)
Posted: May 15, 2012
A member of the borage family, it is commonly known as Siberian bugloss or perennial forget-me-not. In late spring, clusters of dainty, soft blue flowers dance above the heart-shaped foliage. The coarse five to six-inch leaves are lovely juxtaposed against the finely dissected foliage of ferns, bleeding hearts, and other herbaceous perennials. Heartleaf brunnera develops one to two foot mounds and is a good groundcover that will naturalize under proper growing conditions. If reseeding is undesired, deadhead the flowers after bloom. In mid-summer, declining older leaves may be cut to the ground to stimulate new growth. Anecdotally, many dogs are attracted to brunnera and happily munch on the foliage.
Is ‘Jack Frost’ brunnera a perfect plant for the shade? Well, almost—one problem that frequently plagues ‘Jack Frost’ is foliar nematode. Symptoms generally appear in mid-summer. Triangular brownish-black blotches appear between the veins of the foliage, leaving the leaves looking scorched and desiccated. The presence of foliar nematodes can be confirmed by harvesting several leaves, shredding them and soaking them in a jar of lukewarm water for 12 to 24 hours. The nematodes move into the water and are visible with a compound or dissecting microscope. Look for very small, translucent roundworms swimming in the water. It may take a few minutes to recognize the nematodes because they are clear, but once you do, it is a relatively simple diagnosis. You can also call your local county extension office for information.
Unfortunately, there is no product available to completely control the nematode. Foliar nematodes feed within the plant tissue, and in moist conditions will spread to other nearby herbaceous plants. The best solution is to purge any infested plants from the garden. View photos of foliar damage.
In neighborhoods heavily browsed by deer, Siberian bugloss is an excellent substitute for the beloved hosta, and with its many outstanding features, ‘Jack Frost’ brunnera is a superstar of the woodland garden.