Digging In: Advice on Plum Tree Alternatives, Topping Trees

By Scott Aker
Special to The Washington Post
Thursday, July 23, 2009

Q Can you recommend a plum tree that would grow to 30 feet, shade a sunny corner of my house, bloom fragrantly and produce fruit? The site is hilly and has sandy soil. I recall seeing a Myrobalan plum growing well in such a hot, difficult spot. Would you recommend that, or others?

A Plum trees grown for fruit are smaller than you describe because they have been bred to be small enough for easy harvest. Sour cherries approach the size of tree that you describe and might be able to fulfill your need for shade and fruit.

Myrobalan plum, also known as cherry plum, is often used as the rootstock for plums and apricots because its roots are more adaptable to heavy soils. Purple-leafed selections of this rootstock are often grown as ornamentals -- Thundercloud being the most commonly encountered cultivar -- but they do not normally bear fruit. Thundercloud doesn't grow much taller than 20 or 25 feet and doesn't provide much shade. The chokecherry, Prunus virginiana, may reach up to 30 feet in favorable conditions. Schubert is a selection with purple foliage. The astringent fruits may be used to make jam.

Most plums do not have strongly fragrant blossoms. The related Japanese apricot has the most fragrant flowers in the genus Prunus. I would highly recommend it, since it tends to be a more adaptable tree that is less prone to disease and insect problems than many similar small, flowering trees. Although the fruits are wonderfully fragrant when ripe, they are rather insipid.

If you want the best of both worlds, plant a Japanese apricot or one of the larger crape myrtles, perhaps Natchez, for some shade, along with a pluot or plum of your choice for fruit. You will have to protect the young fruit from the plum curculio, a beetle, if you expect a harvest. Spray the tree thoroughly with a residual pesticide labeled for curculio when the flower buds first show color and again when the petals are falling. It may also be necessary to apply an orchard fungicide to prevent brown rot, particularly in wet weather.

Over the years, the bottom branches of my Leyland cypress and hemlock have become thin and straggly. Can I top them to promote regrowth of lower foliage?

Leyland cypress and hemlock, like the vast majority of conifers, cannot sprout new branches from old growth. All of their growth takes place at the branch tips.

If you cut the tops off, you will allow more light to penetrate to lower branches, and if there is living tip growth on them, they will grow. The effect is generally less than attractive and may make you want to start over completely. If you do, choose a dwarf variety of hemlock such as Sargentii, or plant Hiba arborvitae or American holly, both of which retain their lower branches quite well, even if grown in shade. You can even prune the holly back if it gets too large since it is able to sprout new growth from old branches.

Scott Aker is a horticulturist at the U.S. National Arboretum.

© 2009 The Washington Post Company