Growing Concerns 604: Kalmia latifolia, live christmas tree


Growing acid-loving plants is a challenge in southeast Michigan

Dear Janet,

I want to grow mountain laurel (Kalmia latifolia) and wonder if anyone in around here has any experience with them.

In particular I wonder how much sun they need. Different nursery catalogs and web sites have conflicting recommendations for them to be placed in full sun, partial shade or shade. And I have run across comments ranging from "does not thrive in full sun" to "tends to exhibit sparse and irregular branches and blooms infrequently when placed in shade."

I am looking at putting them on the northwest side of my house in an area that only gets a little sunlight very late in the afternoon.


 Dear J.A.,

Kalmia latifolia is a broadleaf evergreen with showy spring flowers. It's native in acidic soil areas of the northeastern U.S., in and along the edges of older forests of mixed pine and oak. It grows below high-limbed trees where openings admit light, not in the dense shade of closely spaced, low-branched young trees.

Growing Kalmia in alkaline soil is do-able. But it's a challenge as is growing others in the acid-loving heath family, such as rhododendron, blueberry, heather and Pieris japonica.

More energy means better bloom. So plant Kalmia in as much sun as possible, at least 6 hours of light per day during the growing season. Count November and March sun, since these plants can photosynthesize any time it is not so cold or dry that their leaves roll up. Choose a spot that's like a woodland -- protected from drying winds, with an overhanging canopy that tempers daily temperature fluctuations and soil that is always cool and moist without ever being soggy.

Amend the soil with organic matter and soil sulfur to make it loose, well drained, moisture retentive and acidic. Mulch with acidic materials such as pine needles, cocoa hulls or coffee grounds. Fertilize at intervals during spring and early summer with acid-loving plant fertilizer. Water faithfully, preferably with a slow drip from April through October.

Even at its best, Kalmia latifolia becomes open in the center with age. To counteract this, prune established shrubs to cut out two or three stems close to their bases every spring. This will keep new growth coming in the center.

Contradictory recommendations are understandable, since these plants are grown across a wide area. In the heat of the South, too much sun will kill them. Under low branched maples on a lawn where it's shadier than in an old woods, these plants may not get enough light to be full or bloom well.

Short report

Sorry, you can't root and grow a cut Christmas tree

In a January 15 short report I wrote, "You can transplant that live Christmas tree."

N.G. writes that she and family have had, "quite a discussion about this. We do not understand your definition of a Christmas tree. Do you mean one that has been cut and decorated for Christmas? ...when you talk about a root ball that mixed me up."

 I meant a tree used as a Christmas decoration yet intact, with roots still potted or in burlap wrap.

To gardeners who think it must be rare for people to imagine a cut tree being replanted: Dispel that notion. Remember that what you do can seem magical to others. One time I learned only by accident that a man who overheard me talking about planting a Christmas tree also had a cut tree in mind. He had decided that my green thumb extended into the supernatural range.


I enjoy answering questions you mail to me or post on my school's website. However, some problems have no solution. Don't expect much help from me if you pose a "stumper" such as: Why is it that people who like intricately curving bed edges usually find themselves sharing yardwork with someone who is only willing or able to mow along straight lines and simple bends?


Green thumbs up

to the Building Industry Association representatives who encouraged development of and then attended the class "Avoiding Construction Damage to the Landscape" at The Michigan School of Gardening. They showed their willingness to learn about the specific impact their work has on a landscape, what constitutes effective plant protection and how they might assist clients who plan to preserve their landscapes. Ask if your builder or remodeler has done this. Or, take the class yourself. It's for both builders and property owners.


Green thumbs down

to construction workers who insist on parking within arm's reach of their work sites because, "I need things in my truck and it's costly for me to walk back and forth all day." When you drive on lawns and gardens you damage soil, roots and plants immediately and in ways that can take decades to remedy. Rethink your position in light of that greater cost. Or consider the fact that my carpenter grandfathers as well as today's plumbers, professional gardeners, arborists and even me, in my first career installing phones and wires, could plan well enough to work efficiently from trucks parked on the street.

 Originally published 2/5/05