A Blush of Color Ushers In Spring
As any gardener knows, Colorado’s spring weather is uneven. Snow showers may follow a summery day in April and temperatures fluctuate wildly. For a brief period of time crabapple trees bloom with their showy white or pink blossoms and we are lulled into believing that warm weather is here to stay.
As hardy transplants rather than natives, crabapples can take our cold, shift in temperatures, semi-arid climate and brisk winds. With sweeping branches, symmetrical shapes and modest proportions, crabapple trees fill a niche along the Front Range. Even if blossoms are swept away by the wind within a week’s time, we love and savor their ephemeral beauty. By the end of summer, varieties that set small fruit will provide food for wildlife.
James Klett, professor at Colorado State University in Fort Collins, has studied about 65 to 70 cultivars of crabapples for the last 15 years. “Crabapples are an adaptable tree, good for residential planting—not so large as a shade tree. They are so beautiful and some have wonderful fruit,” he says.
All apples belong to the Malus family, which offers a thousand or more cultivars. The crabapple is a genuine apple tree that bears a small fruit—an apple of less than two inches in diameter. But unlike most larger apple varieties, it’s particularly hardy in Colorado, with one exception. Fire blight–a stubborn plague in our region—can attack apple trees. The other scourges of crabapple trees rarely show up here. As long as you can prevent or discourage fire blight, you will have a hardy and beautiful tree.
“When we began our evaluation for fire blight resistance, back in the 1980s,” James says, “there was a national program to look at 65 or 70 cultivars. They needed a lot of light and not a lot of humidity. Consequently, CSU became one of the areas for this region. Back then only about five or ten were widely planted and grown.” Rather than try to fight the disease, he recommends that gardeners choose from the number of cultivars that he discovered were more resistant.
‘Adams,’ ‘Centurion’, ‘Henning’, ‘Indian Summer’, ‘Ralph Shay’, ‘Zelkirk’, and Malus baccata var, jackii—all have proved to be good choices for Colorado landscapes. “Fire blight is worse in some years than in others,” James says, “but there are a lot that are resistant, just plant those. In other parts of the country you’ll find apple scab or cedar apple rust—those diseases are more of a problem elsewhere. Crabapples are usually from Asia, North America or Europe and the Asiatic are more resistant to diseases.”
Aside from the typical upright tree, the crab apple tree comes in weeping, shrub, and columnar, spreading or round shapes. When in bloom, a spreading or weeping-shaped tree can be spectacular—a form of living sculpture. Even if blooms are short-lived, the shapes and sizes of crab apple trees can be stunning when not in bloom.
“A lot of crabapple trees are grafted, many on Siberian rootstock. I think that what you are seeing today is more that have multi-stems, grown as large shrubs for small yards and also trees that have no fruit at all. ‘Coralburst’ comes to mind. You also see some that are grafted to be a patio tree. Some get a bad name because they drop their fruit. But if you don’t like the fruit, you can plant those that hold their fruit. The small apples do provide wonderful food for wildlife, and my own choice would be a cultivar that holds its fruit,” he says.
Mid-March to mid-April is the best time to plant a young tree. You can get away with planting a tree in the fall, before mid-October, but the early spring is preferred. To plant a tree, dig a hole with about a foot larger around the root ball and then mix some compost with the existing soil. Some experts allow only about one-fifth of the soil to be compost, others will add as much as one-third. Plant the tree away from any lawn because excessive watering—often the amount required for a lawn—is the most common reason why a young transplanted tree dies.
A new tree will require infrequent but deep watering. Dig into the soil around the root ball and feel if the soil is damp. Often, soil that appears very dry on the surface will be damp just a few inches below. If the soil is dry down to six or ten inches, it’s time to water. In time, crabapple trees will become drought-tolerant.
Crab apples tend to send up suckers from the roots. It’s best to remove these during the times when apple trees are pruned—in the middle of winter, perhaps January or February. To discourage the spread of fire blight, a bacterial disease, tree trimmers cleanse their shears with rubbing alcohol or bleach. Still, bees, aphids and leafhoppers, can spread the disease, too. It’s obvious to the naked eye because the limbs turn dark and look burned or withered. Eventually the blight spreads and the entire tree will die. Fire blight begins at the new growth tips of the tree and usually is clipped back to prevent its spread.
- Thundercloud, Radiant, Profusion, Adams, Indian Summer
- Sentinel, Centurion
- David, Lancelot, Guinevere, Camelot, Thunderchild (purple flowers and purple leaves)
- Red Jade, Coral Cascade, White Cascade, Louisa
- Coralburst, Brandywine, White Madonna
Resources: Planttalk, a service of Colorado State University Cooperative Extension www.ext.colostate.edu/ptlk, provides telephone information about planting trees at 888-666-3063.
Helpful websites: www.malus.net, The International Ornamental Crabapple Society.