Black cohosh seems to prefer cool, moist home

Q: I’ve tried to grow Cimicifuga for years with little success. Any tips? – Y.M., e-mail

A: Cimicifuga, also commonly called black cohosh, black snakeroot or bugbane, is a striking plant that grows to more than 6 feet in height in a suitable environment. Beautifully toothed leaves and upright wands of fine, white flowers make the plant a handsome addition to the background of a perennial border.

While its beauty is alluring, as Y.M. points out, Cimicifuga can be a fussy resident of the perennial bed. References often indicate that the plant may be grown in full sun or partial shade. However, black cohosh seems to prefer moisture over direct sunlight and tends to grow best under partially shady conditions, where the soil maintains moisture throughout the heat of summer.

If the plant is grown in full sun, the gardener should be sure to amend the soil environment with a heavy application of rich organic matter. A mixture of well-composted manure, leaf litter and garden compost should be mixed into the soil profile around the planting.

Black cohosh is really a cool-loving plant. During terribly hot, dry summers, the plant seems to suffer prematurely even in the naturalized woodland settings to which it is indigenous. However, the gardener should note that once a suitable place in the landscape has been found for this magnificent plant, it is relatively long-lived and maintenance-free.

Q: What’s the best way to overwinter an expensive rhododendron? – N.H., Mars Hill

A: In some areas, rhododendrons require no assistance in enduring Maine winters. In other areas, however, the combination of bright daylight, high wind and intense cold makes for difficult conditions for broadleaf evergreens.

In general, the plant tissue of a rhododendron is fairly hardy to ambient winter temperatures in most of Maine. The difficulty associated with overwintering these lovely spring- and summer-blooming plants is that their leaves may require some protection from the winter elements.

First, note that unlike deciduous shrubs and trees such as the lilac and maple, plants that retain their leaves throughout winter – evergreen plants – continue to undergo photosynthesis and other metabolic processes year-round. This means that evergreen needles and broad leaves lose moisture through tiny holes in their undersides year round. In winter, this process poses some difficulty, as the plant cannot easily replace the moisture lost through the leaves as it would during active growth in the summer.

“Leaf burn,” a deep reddening of evergreen leaves, is a sure sign that a plant has been exposed to sun and wind and has been unable to keep up with replacing the moisture lost through that exposure. In spring, the collective destruction of these leaves can have a serious impact on the form of the plant.

By erecting a wooden “tent” over a rhododendron or by wrapping the plant in burlap and securing the fabric in place with twine, the gardener limits the sunlight – and hence the moisture loss – from the leaves of the plant. Keep in mind that air flow must be maintained through the canopy of the plant, so never wrap one in plastic. Burlap provides benefits of limiting sunlight and offering air penetration. It is inexpensive and easy to apply.

Q: What is a wattle fence? – A.M., Belfast

A: Wattle fences are traditionally made by weaving small saplings together to form a barrier around a garden or – if low in stature – around a raised bed. During the construction of a wattle fence some saplings are stripped of their lesser branches and leaves and are driven into the ground as stakes. Others are stripped and used to alternately weave through the stakes. These inexpensive fences made with materials from the local environment date at least to Colonial times in America.

Diana George Chapin is the NEWS garden columnist. Send horticulture questions to Gardening Questions, 512 North Ridge Road, Montville 04941 or e-mail dianagc@midcoast.com. Selected questions will be answered in future columns. Include name, address and telephone number.