Honey locust trees (Gleditsia triacanthos) have been admired for centuries, but the native species has thorns and seed pods that cause major cleanup issues, which limits its appeal for homeowners. Plant science has, however, given us a number of podless, thornless honey locust cultivars that are much more suitable for landscape use.
One such well-behaved cultivar is usually known by its registered trademark name, Sunburst®. The official cultivar name is Gleditsia triacanthos var. inermis 'Suncole'; it was created through selective manipulation of a thornless variation of the native species. 'Suncole' is somewhat shorter than the native species, growing to about 40 feet vs. the 80 feet of the native tree. The podless/seedless characteristic derives from the fact that commercially offered trees are typically male cultivars.
Honey locust is a member of the pea family, along with well-known landscape plants like lupine and wisteria. The compound leaves are fern-like, with a fine texture, and the branching pattern is relatively open and airy. The new foliage starts out yellow, then morphs to a still attractive greenish-yellow, before assuming a plainer light green shade in summer. When it is time for the fall display, the leaves return to the yellow color that marked them in spring. These are tough, fast-growing trees that are tolerant of challenging urban conditions, such as drought, pollution, salt, compacted soil, heat, and alkaline soils.
|Botanical Names||Gleditsia triacanthos var. inermis 'Suncole'|
|Common Name||Sunburst honey locust|
|Plant Type||Deciduous tree|
|Mature Size||30 to 40 feet tall, 25-foot spread|
|Sun Exposure||Full sun|
|Soil Type||Tolerates most soil types|
|Soil pH||Tolerates all pH levels|
|Bloom Time||Spring, summer|
|Hardiness Zones||4 to 9 (USDA)|
|Native Area||North America|
How to Grow Sunburst® Honey Locust
This tree has few restrictions on how to grow it; the only place it struggles is in dense shade. It is an ideal tree to plant in locations where you want filtered shade rather than the deep shade created by many other landscape trees. It's a good lawn tree since it allows plenty of filtered light to reach down to the grass. Keep the tree well-watered, and make sure to protect the trunks against damage from lawnmowers and other lawn equipment, as the bark is tender and prone to injury. Applying a ring of mulch such as shredded wood or bark chips around the base of the tree is a good idea, as it will keep mowers away from the trunk.
Honey locusts are somewhat susceptible to a variety of insect pests, including spider mites, gall midges, and webworms. Pests can be treated with organic sprays, and are less likely to be serious problems if you keep the trees in good condition by adequate watering and regular removal of dead and damaged branches. They are also attacked by diseases such as leaf spot and canker.
Full sun is preferred by these thornless honey locust trees, although young trees will grow well in partial shade.
The honey locust tree is a very hardy tree and can grow well in different types of soil. Loam is ideal, but the trees are also quite tolerant of sand or clay. This tree is also tolerant of salty soils.
Honey locusts have a moderate tolerance for flooding, drought, and other adverse conditions. They thrive in both moist or dry soil. Trees should be watered as soon as they are planted and weekly for the first year. A one-hour trickle that slowly saturates the roots provides proper water for a new tree. Adjust watering based on the local rainfall.
Temperature and Humidity
The honey locust is able to grow in a variety of climate conditions, but it will perish if exposed to temperatures below minus 33 degrees Fahrenheit.
Older trees rarely need additional irrigation or fertilizing, especially if they are in an irrigated, fertilized lawn. For newly planted trees, you can try an evenly balanced 10-10-10 or 20-20-20 granular, stake, or liquid fertilizer. An organic fertilizer such as manure is another good option.
Propagating Sunburst Honey Locust Trees
Sunburst is not a tree that lends itself easily to DIY propagation, though you may have success by taking cuttings, coating them with rooting hormone, and planting them in a growing medium until roots form. In the commercial industry, thornless or podless varieties are generally grafted onto the rootstock of a native honey locust.
Mature honey locust trees need little pruning except to remove dead or diseased branches, but until they are mature, you should prune them every five years or so to shape them as desired. This typically means keeping the canopy relatively open and airy. Branches that cross and rub can be susceptible to developing canker, which can spread and kill a tree. The best time to prune is in late spring to fall when sap flow has lessened somewhat.
Comparison With Other Cultivars
Thornless honey locusts are all members of the inermis variation, and the podless/seedless varieties are typically male cultivars. Some other varieties you can consider include:
- Imperial™ (Gleditsia triacanthos var. inermis 'Impcole'): This is a more compact cultivar (35 feet) that produces a few seed pods.
- Moraine (Gleditisia triacanthos var. inermis ‘Moraine’): This is a seedless male cultivar with small dark green leaves that turns golden yellow in fall.
- Northern Acclaim (Gleditsia triacanthos var. inermis 'Harve'): This seedless male cultivar is cold hardy to zone 3; it grows 45 feet tall.
- Perfection (Gleditsia triacanthos var. inermis 'Wandell'): This is a seedless male cultivar that grows 50 feet tall.
- Skyline (Gleditisia triacanthos var. inermis ‘Skycole’): This male (fruitless) cultivar has a pyramidal shape.
- Street Keeper™ (Gleditsia triacanthos var. inermis 'Draves'): This is a narrower tree (20-foot spread) that produces some seed pods.