Chapter 96 Gleditsia triacanthos
96.1 Honey locust
Canopy of a honey locust in open ground, in full fall colors. Link to original image.
96.2 Soil: General Deciduous / Rich Conifer Mix
Ratio: 3 parts bark, 1 part grit
Add-ins: dolomitic limestone (~5 lbs/yd), Tree-Tone (15 lbs/yd)
pH: ~6.5 (slightly below neutral)
Moisture: Average
96.3 Light
Routine: full sun.
Summer: no experience yet.
96.4 Cultivation Notes
96.4.1 Potting & Root Pruning
Schedule: repot every two to three years in spring as buds extend.
96.4.1.1 Top & Branch Management
Close-up of emerging foliage on a honey locust. Link to original image.
Heavy pruning: to develop structure, prune branches hard in late winter.
Fine pruning: shorten new trunk shoots in summer. Trim new growth as necessary.
Leaf pruning: do not leaf prune.
96.4.2 Feeding
Feed every two weeks throughout the growing season.
96.4.3 Pests & Problems
Honey locust is susceptible to a large number of potential disease problems, including leaf spot, canker, witches’ broom, powdery mildew and rust. Borers and webworms are common insect problems in some areas. Gall midges on foliage may be a problem.
96.4.4 Winter Storage
Protect from frost below 25°F to avoid twig dieback.
96.5 Propagation Notes
Sow scarified seed outside in fall. Thornless cultivars may need to be purchased as liners.
96.6 Artistic & Styling Notes
Informal upright forms with single or multiple trunks in small to medium sizes. I have seen some examples of bonsai, but not enough to say with any confidence that it will adapt well to training.
96.7 Additional Information
96.7.1 Natural History
Honey locust is a spreading, deciduous tree with a spiny trunk and shoots. Native to North America from Pennsylvania to Iowa south to Georgia and Texas. It grows to 100 feet or more. Glossy, pinnate dark green leaves to 10 inches long, turn yellow in fall and are composed of 14-24 leaflets. There are a number of thornless cultivars.
Inconspicuous, greenish yellow to greenish white flowers appear in racemes in late spring. Flowers are followed by long, twisted and flattened, dark purplish-brown seedpods (to 18” long) which mature in late summer and persist well into winter. Seedpods contain numerous flattened, round seeds surrounded by a sweet, sticky pulp.
96.7.2 In Cultivation
Honey locust is susceptible to a large number of potential disease problems, including leaf spot, canker, witches’ broom, powdery mildew and rust. Borers and webworms are common insect problems in some areas. Leaflets are too small to rake, which is good, but seed pods are unattractive on the tree and messy when they fall. Thorns on species plants can be just plain nasty.