IN THE GARDEN

By Doreen Trudel

Unseasonable snow is falling as I write this column so the typical list of May chores and planting advice must be discussed with a word of caution. Before planting annuals or tender perennials, hardening-off seedlings or retrieving container plants from their winter protection check the weather report. Generally in our climate it is safe to plant all temperature-sensitive plants after Mother’s Day but this year I would make sure that daytime and night time temperatures remain above 50 degrees Fahrenheit or 10 degrees Celsius before adding tender plants to the garden.

In my walks or drives around the area I see that many gardeners are realizing the benefits of incorporating some of the older, larger fir, cedar and hemlock evergreen trees into their landscapes. They look beautiful and elegant with just mulch beneath their dramatic canopies but in a smaller garden a stand of evergreens is frequently located near the front driveway or off a back deck where the addition of colorful or textural interest would be appreciated.

I am sure we have all heard tales that nothing will grow beneath a cedar tree because it produces a toxin which is fatal to other species. Horticulturalists and arborists with more knowledge and experience than I are beginning to say that the stories about the allelopathic properties of Thuja (western red cedar) or Cedrus (true cedar) have been exaggerated.

It is true that these trees produce hormones and oils which are designed to repel insects and provide protection from disease but if you walk through the woods you quickly realize that there are many plant species coexisting beneath the evergreen canopy.

Anecdotal evidence that I have read and heard supports the idea that lack of sunlight, water and competition for root space are the true reasons for the death of companion plants under a cedar tree.

These factors can be addressed so we no longer have to choose between evergreen trees or flowers in our gardens. With some thoughtful planning and a little extra care we can have both our lovely cedar trees and a colorful, varied and rewarding garden bed.

To lessen the competition for root space, plant smaller-sized starter plants. This is pretty basic advice but I too am impatient when planting. I dream about mature gardens and that’s what I want to see in my landscape but choosing small sized pots allows the plants to mature into the root space and it also means you do not disturb the roots of the existing trees. Decorative pots of larger plants can be added in the bed to provide instant height and interest. My knowledgeable sources say that large amounts of soil should not be added beneath an old tree. Adding soil only encourages shallow unstable roots to grow up into that newer, richer soil. This would only be a temporary solution as the roots would soon be competing once again in the new soil layer.

Lack of water is probably the greatest threat to shrubs and perennials planted around cedar trees. The roots of the large evergreens take up much of the water in the soil surrounding the tree. The dense canopy keeps the rain and snow from reaching the soil within the drip line of the trees so for all plantings you will have to provide some water depending upon the plants needs.

There are many plants that thrive in dry shade conditions but even for these species you will have to water them at least until they are established and possibly during our driest months of July and August and until the fall rains begin. An above ground drip system would work well and it would be hidden by a layer of mulch.

Dealing with the lack of sunlight under the evergreens is the easiest problem to solve. Choose only acid loving plants that tolerate dry shade. Do not try to turn a stunning Pacific Northwest evergreen forest into a sunny bright flower-filled English cottage garden. Both are beautiful. Both have their own charms but they make strange bedfellows.

If the garden bed extends beyond the drip line of the trees there are even more design possibilities and greater plant options. Mother Nature has designed a wonderful garden without our assistance but it is good to know that with thought and care our horticultural desires can coexist with the native landscape.

The Point Roberts Garden Club has changed meeting days. The next meeting will be on Tuesday, May 13 at 7 p.m. at the community center on Gulf Road.

As a resident of beautiful Point Roberts I want to thank everyone who contributed in any way to saving Lily Point … you deserve a group hug.

Plants to Grow Under a Cedar Tree

Here are a few suggestions of shrubs and perennials that have grown successfully beneath an evergreen canopy.

Shrubs: Mahonia nervosa (low growing Oregon grape), Epimedium, Vancouveria (inside-out flower) Vaccinium parvifolium (red huckleberry), Vaccinium ovatum (evergreen huckleberry), Gaultheria shallon (salal will spread very easily), Sarcococca confuse, Skimmia japonica, Cotoneaster, Leucothoe, Rosa nutkana (Nootka rose native to this area). Most of these shrubs are evergreen.

Perennials: Tellima grandiflora, Tolmiea menziesii, Chelidonium majus, Euphorbia sikkimensis, Geranium macrorrhizum, Luzula sylvatica ‘Aurea’, Pachyphragma macrophyllum, Ranunculus aconitifolius ‘Flore Pleno’, Saxifraga ‘Tricolor’, Tradescantia Andersoniana group, Polystichum munitum (western sword fern), Adiantum aleuticum.