Finding tree species that do well in compacted clay soil can be a challenge. If you have alkaline soils, it further complicates the process.
Species selection is critical to long-term success of city trees. Here are three common trees that are more tolerant of compacted or alkaline soils:
- Hawthorn trees (Crataegus sp.) - Trees range in size from shrubs to trees that can reach about 40 feet. Some varieties have thorns. As members of the Rosaceae family, they bloom in late spring and develop a pomme-type fruit similar to a crabapple or rose hip in late summer. The fruit is attractive to wildlife and edible by humans. The tree has a dense, twisted branch habit that makes its shape interesting year-round. Hawthorns will tolerate clay soil and a wide range of soil pH. They are very cold hardy and drought tolerant once established. Good varieties include Russian Hawthorn (Crataegus ambigua), Cockspur Hawthorn (Crataegus crus-galli) and Toba Hawthorn (Crataegus x mordenensis 'Toba'). This tree can be a good alternative to flowering crabapple trees.
- Ohio buckeye (Aesculus glabra) - Also known as horse chestnut trees, these trees reach heights of 50 feet to 80 feet. They are a good choice for street shade trees. Since they can be as wide as they are tall, give them plenty of room. The leaves are opposite, palmate and compound-shaped with five leaflets. Yellow flowers on panicles appear in the spring, followed by a nut-like fruit. The nuts are not edible for humans or livestock because of their high tannic acid content. While these trees prefer moist, well-drained soil, they tolerate alkaline soils. They are susceptible to leaf scorch during hot, dry periods so regular watering is important. This tree can be a good alternative to a maple tree if you have alkaline soils.
- Weeping white spruce (Picea glauca pendula) - While the standard form of Colorado blue spruce might grow too large for a small lot, there are some cultivars that do not grow as tall or wide as the standard spruce. Pendula is a cultivar that grows to about 25 feet and is tolerant of many soil types, including alkaline. Because it has a weeping growth habit, the branches are held close to the trunk, limiting the width of the tree and promoting a spire-like appearance. It requires moderate water and is a good specimen tree that will add evergreen color to your landscape without becoming so large that it dwarfs your residence.
When you have questions, Colorado State University Extension has research-based answers.
Get answers to your horticulture questions by calling a Master Gardener volunteer at 520-7684 or emailing CSUmg2@elpasoco.com.