Few trees are more versatile and useful in a home garden than the Washington hawthorn (Crataegus phaenopyrum), a medium-sized tree that has bright white flowers in spring, colorful leaves in fall and berries that often last on the tree into winter. It works well as part of a screen planting, a mixed border or a specimen. The tree blooms dependably after a few years if you start with a grafted specimen.
Color, Color, Color
The Washington hawthorn is a deciduous tree that's usually about 25 feet tall when mature, although some specimens can be taller. It's a low-branching, broadly spreading tree that grows in U.S. Department of Agriculture plant hardiness zones 4 through 8. This species is later-blooming than other hawthorns, putting out attractive clusters of white flowers in late spring, usually toward the end May or in early June. It's young leaves emerge reddish-purple, turn green and then become orange, scarlet or purple in fall. Small red berries follow flowers, attracting birds and other wildlife.
Look For The Graft
The Washington hawthorn is moderately fast-growing, adding about 1 or 2 feet to its height each year. To ensure that a new tree blooms as soon as possible, plant a grafted specimen rather than a seedling tree. Most nursery specimens are grafted, with the upper part of the tree taken from an older hawthorn and grafted to a vigorous rootstock. A grafted tree matures relatively quickly, producing flowers and fruit by about four or five years after planting. You might also see a young nursery tree that's been grown from a seed, which matures more slowly and may take 20 years or more to flower. When choosing a tree, look for the grafting scar near the base of the trunk or ask for detailed information about a tree.
Keep It Sunny
You can help promote flowering by planting a Washington hawthorn in a spot that gets full sun, where it puts out the best leaf color and produces an abundance of blossoms. It also tolerates a few hours of shade each day, but this could lessen flowering. The tree is exceptionally tolerant of all types of garden soil, even compacted, dry soils with low fertility. It grows best when given good drainage, so if your soil contains clay, add some coarse sand at planting to improve its drainage. The tree adapts well to drought once established, but giving a newly planted tree moderate, even moisture during its first few years helps give it a good start.
Keep It Problem-Free
The Washington hawthorn's foliage attracts several pests, including aphids, lace bugs and leaf miners, which can damage its foliage and flowers. You can control these by spraying when needed with insecticidal soap, diluted at a rate of 5 tablespoons per 1 gallon of water. Tent caterpillars sometimes build their tents in a hawthorn. These are best pruned off when small, or caterpillars can be destroyed with insecticidal soap spray when still tiny, with the spray mixed as for other insects. Several fungal diseases, such as leaf blight or hawthorn rust, can damage leaves or cause them to fall. These are best prevented by planting in a spot with good air circulation, clearing debris from under the tree regularly, watering only at the root zone and keeping the foliage dry.