From the Desk of Ed Hume: How to Grow Plants Under Tall Trees

April 21, 2010 at 12:00 AM Leave a comment

If you have large trees on your property, you probably know how difficult it can be sometimes to grow plants under them. A rather common garden question is “What plants will grow under a tall tree?” The answer is really quite simple. It isn’t a matter really of which types or varieties to grow, but instead is the importance of providing the proper care for the plants so they can compete successfully with the robust root growth of the tall trees.

When you visit places like the University of Washington Arboretum, Butchart Gardens, or established residential plantings you often see a wide variety of plants grown under tall trees. For example, in the camellia section at the University of Washington Arboretum you will find the plants growing under tall trees. Needless to say, this is only one remote example. There are countless similar plantings throughout the Pacific Northwest. In each case the success of the plants is the result of proper watering, adequate drainage, fertilizing, light exposure and seasonal pruning attention.

One of the most important factors to keep in mind when selecting plants to grow under tall trees is ;t, the overspreading branches will provide a certain amount of shade, therefore it is important that you select plants that will crow and flower best in this type of an environment. That is why you will so oft3n see rhododendrons, camellias, azaleas, viburnum dafidi, metal, and other similar plants growing under tall trees.

Some of the finest plants to grow under tall trees are our natives, including such plants as salal, kinnikinnick, and mahonia. A few other topnotch plants include hosta, ferns, skimmia, sarcococca and many other broad-leafed evergreens. Some of the best ground covers to grow under tall trees are vinca minor, ivy, salal and kinnikinnick. Needless to say, these are only some of the most popular plants to grow under tall trees. In planting locations where the sun shines for several hours, reaching the plants under the trees, the list of the types of plants that could be grown is almost unlimited.

The major problem experienced in growing plants under tall trees is the encroachment of the tree roots into the planting areas where the shrubs are being grown. Since the tree roots are so dominate they tend to rob valuable nutrients and moisture from the smaller growing garden plants. Here are a few pointers on ways to keep your plants healthy and in top-notch shape in such planting locations.

Special attention should be given to watering plants under a tall tree. Large trees use copious amounts of water and as a result, the soil under the trees tends to dry out quite rapidly so the plants will require more watering attention than those grown in the open garden. In fact, it may be necessary to provide special watering consideration even during the winter months. The addition of peat moss, compost, or processed manure added to the planting area at planting time will greatly aid in holding moisture around those shrubs that are planted under tall trees.

Since the tall trees rob valuable nutrients from the lower growing base plantings, it may be necessary to feed the plants a little bit more frequently. The best time for fertilization of these plants is in late February and again in early June. If necessary, a third application could be made in early July. Since the tree roots tend to encroach the planting area of the base shrubs it is often a good idea to apply a liquid fertilizer in a foliar application rather than applying the dry fertilizer on the soil. Fish fertilizer or other types of liquid fertilizer, which can safely be applied to plant leaves, can be used for foliar feeding. Read and follow application directions on the label of the product you use.

Another prime consideration in growing plants under tall trees is that of proper light exposure. Often it is a good practice to remove some of the lower-growing branches on the trees so that the plants underneath will receive as much indirect light as possible. The pruning of these lower limbs can be done at most any time of the year, but is best done during the winter dormant season from November to March.

The shrubs grown at the base of these tall trees often will require more pruning attention than those grown in the open garden. This is often due to the fact that the plants receive less light, inadequate water, or insufficient fertilization. Because of these factors the plants sometimes tend to grow straggly or uneven and a simple light pruning will often bring them back into shape and help create a bushier, neater appearing plant. Most broad-leafed evergreens are best pruned during the spring months of March, April and May, while the deciduous type plants can be pruned during the winter dormant season.

When planting any shrubs under tall trees, be certain that they do have adequate drainage. Clay or hardpan type soils often retain too much moisture for many types of broad-leafed evergreen shrubs. If the drainage problem is severe, it may be necessary to tile away the excess moisture.

You can grow many plants successfully under tall trees if you give the plants the care they need.



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From the Desk of Ed Hume: Spring Flowering Shrubs Clip of the Week: Grooming Houseplants

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