Margaret Lauterbach

Among shade tolerant plants, the trillium shines

Margaret Lauterbach has the answer: What gardening zone are we in?

Idaho Statesman gardening columnist Margaret Lauterbach gives the definitive answer to the pesky and perennial question: Which zone are we in? Plus she has a few key pieces of advice specific to Boise gardeners.
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Idaho Statesman gardening columnist Margaret Lauterbach gives the definitive answer to the pesky and perennial question: Which zone are we in? Plus she has a few key pieces of advice specific to Boise gardeners.

My shade bed in the backyard is finally coming together thanks to self-seeding of Brunnera and the spread of Solomon’s Seal, as well as the intrusion of the thuggish lemon balm. I especially enjoy the sky blue blossoms of Brunnera (Siberian bugloss) in early spring, following white snowdrops and the yellow winter buttercups, winter aconite.

Those Brunnera blossoms are small, less than half an inch across, but the vivid color catches your attention. I have three varieties of Brunnera in that bed, including Jack Frost and Variegata. Blossoms don’t differ among varieties, but the variegation on leaves does differ. Jack Frost has nearly white leaves, with green veins, and Variegata has broad white leaf margins.

The star of that bed, though, is trillium. I bought one trillium several years ago from Walmart, Better Homes & Gardens brand, said to be “not wild-collected.” Digging trilliums or harvesting their seeds from national forests is illegal, so I’ve tried to buy more, never timing the effort correctly. I thought I had just the one plant, but this spring I spotted three trilliums in bud. They have variegated leaves and dark purple blossoms, unlike the wild trilliums in our mountains. Those wild ones I’ve seen bloom white, at the same time morel mushrooms emerge.

Did I overlook those other trilliums in that bed in the past? I don’t think so. Trilliums take four to seven years to get to blossom stage from seed. These wonderful plants are also called “trinity plants,” since their blossoms have three petals, set above three large arrow-shaped bracts resembling leaves. Those at least with reddish or purple flowers are sometimes called “wakerobins.” Their long development time daunts most nurseries, but Plant Delights nursery in Raleigh, NC, specializes in trilliums. Some trilliums may not survive our winters, so southern nursery owners must just guess at hardiness of their plants since they’re in a warm climate. Plant Delights’ trilliums are not inexpensive, their specimens ranging from $22 to $75 per plant. This is, of course, paying them for their delayed sale, waiting for the plants to come to maturity.

Trilliums, rarely damaged by destructive creatures other than deer, form two main groups: the sessile — flowers on top of the leaf — bract, and the pedicellate — flower is attached to a short stem.

Tony Avent, owner of Plants Delight nursery (and producer of a very witty catalog), says trillium seed is enclosed in a structure called an elaiosome (a fleshy nutritious structure encasing the seed) that ants and other insects take to their nests to share with others. Thus they free the seeds and then discard those seeds in their insects’ “trash dump,” that is actually a rich plant haven in which seeds can germinate.

Trilliums may also be propagated by division. They grow from a rhizome that looks like a coarse carrot. If you wait for late summer or fall to dig them as most references advise, you may find that they’re very hard or even impossible to find. Their ephemeral habit makes them disappear in early summer. If you ignore that usual division advice, and instead dig them while they’re blooming, you won’t lose them but will be able to see the rhizomes and eyes or growing points. To grow, ensure that each new plant has an eye, or growing point. When you dig them while they are blooming, you can tease the rhizomes apart for wider distribution, and after transplanting make sure they have adequate water and care.

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After a number of years, even without being walked upon, the soil in raised beds does compact to some extent. I don’t know why it does, but perhaps it’s atmospheric pressure or the pounding of hard rain or even the soil’s settling into small crevices during snow melt. Fifty years ago, one would be advised to get oxygen to plant roots by using a cultivator. That does stir the soil to a depth of nearly 2 inches. That advice is now rarely given, and cultivators are not in the tool forefront as much as they used to be.

But if your soil in your raised bed is difficult to dig, even to dig a transplant hole, and you know you have abundant organic matter in your soil, you should consider applying either aerated compost tea or Zamzow’s HumaGreen or, last resort, tilling the bed. Of course tilling will disrupt the mycorrhizae and fungi that are working to feed your plants and defend them from destruction, but they’ll quickly recover and re-form their networks. Tilling should last several years in a raised bed before natural compaction returns.

Send garden questions to or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.