Thornless honeylocust

Sun

Full sun; tolerates light shade but develops a better crown in an open position.

Water

Water regularly while establishing; established trees tolerate drought, though prolonged dryness can cause early leaf drop.

Soil

Adaptable to clay, loam and sandy soils, including alkaline and moderately compacted ground. Best in well-drained soil; avoid persistently waterlogged sites.

Height

40-70 ft (12-21 m)

Spread

30-50 ft (9-15 m)

Flowers

Late spring to early summer; small, inconspicuous greenish-yellow flowers.

Foliage

Fine-textured leaves made up of many small leaflets, usually green in summer and yellow in autumn. Some cultivars have golden young growth.

Growth

Fast when young, especially with adequate moisture.

Care needed

Medium

• Buy a nursery-propagated thornless selection; ask separately whether it produces pods.
• Water deeply through dry spells during the first two or three growing seasons, moistening the root zone rather than just the surface.
• Apply 2-3 in (5-8 cm) of organic mulch over the root area, keeping it clear of the trunk.
• Do not routinely fertilize established trees; feed only where poor growth or a soil test indicates a need.
• Stake only if the root ball is unstable, allow some trunk movement and remove ties once the tree is anchored.
• Remove rootstock suckers promptly, especially any bearing thorns.

Pruning. Prune in late winter while dormant to establish a strong main leader and well-spaced branches; remove competing leaders and weak, narrow forks while they are small. Remove dead or damaged wood as needed, and use a qualified arborist for large branches rather than topping the tree.

Late winter

Inspect the branch structure and prune young trees to remove competing leaders and weak forks.

Spring

Plant when the soil is workable and not waterlogged; refresh mulch without covering the root flare.

Late spring

Check expanding leaves for distortion, webbing or chewing before deciding whether treatment is needed.

Summer

Water young trees deeply during dry weather and check that stakes and ties are not rubbing.

Autumn

Collect fallen pods where present and remove unwanted seedlings.

Late autumn

After leaf fall, inspect for dead branches, bark damage and thorny shoots from below the graft.

• Use as a lawn shade tree where filtered light will allow grass to grow better than beneath a dense canopy.
• Place beside a large terrace to provide summer shade without creating a dark outdoor room; choose a low-fruiting selection to reduce pod litter.
• Combine with ornamental grasses and late-flowering perennials for a loose, meadow-like planting beneath an airy canopy.
• Use in spacious urban gardens where tolerance of heat, alkaline soil and some compaction is useful, leaving adequate rooting space away from paving and buildings.

Garden styles it suits: Modern, Urban city garden, New perennial (prairie), Grand estate, Autumn colour and Family-friendly.

Plant it with: Switchgrass, Little bluestem, Purple coneflower, Black-eyed Susan, Catmint and Hardy geranium.

Wildlife: Flowers provide nectar and pollen for insects. Where pods form, their sweet pulp attracts mammals and livestock, which can spread the hard seeds. The canopy provides bird perches and nesting cover; its value to local insects varies outside its native central and eastern North American range.

• Honeylocust plant bugs and leafhoppers can distort or stipple new leaves in spring. Established trees usually tolerate the damage; conserve predatory insects and seek locally approved treatment only for repeated, severe injury.
• Mimosa webworm can bind leaflets together and brown the canopy in parts of North America. Remove small accessible webs early; extensive or recurring infestations may need an arborist's advice.
• Cankers and branch dieback are more likely on stressed or wounded trees. Avoid trunk injuries, water during prolonged drought and prune dead branches back to healthy wood.
• Weak forks and competing leaders can lead to branch breakage. Correct the structure while the tree is young and have mature trees with cracks or large weak unions assessed professionally.

Honeylocust is not known to be toxic to cats, dogs, horses or people, and its pod pulp has a history of food and livestock use. Hard seeds and whole pods can pose choking or digestive risks if swallowed, so do not encourage pets or children to eat them. Do not confuse it with black locust, which is poisonous. Thorny rootstock shoots are a separate puncture hazard.

Where it spreads. Seed-producing honeylocust spreads aggressively in parts of Australia, notably Queensland and New South Wales, and the species is listed as invasive in South Africa. Seeds are spread by livestock and other animals. Thornless trees can still produce viable seed, and seedlings may have thorns; check local restrictions before planting.

• Black locust (Robinia pseudoacacia)

  Usually has larger, rounder leaflets, hanging clusters of white pea-shaped flowers and short, flat pods. Young shoots often have paired spines at the leaf bases; it is poisonous, unlike honeylocust.

• Kentucky coffeetree (Gymnocladus dioicus)

  Has much larger, twice-divided leaves with larger individual leaflets, stout twigs and thick, broad pods rather than honeylocust's long, strap-like pods.

• Silk tree (Albizia julibrissin)

  Has consistently twice-divided, finely feathery leaves and conspicuous pink, powder-puff flowers; honeylocust flowers are small and greenish.

Gleditsia honours botanist Johann Gottlieb Gleditsch, triacanthos means three-spined in reference to the species' branched thorns, and honeylocust refers to the sweet pulp inside its pods.

Propagation. Named thornless cultivars are usually propagated by grafting or budding to preserve their characteristics. Seed requires scarification and does not reliably produce thornless, low-fruiting trees; seedlings may be unsuitable where the species is invasive.

Accepted botanical name

Gleditsia triacanthos

In the US and Canada

Native in Canada and the lower 48 states.

Native range

Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky and Louisiana.

Measured

Soil pH 4.8 to 8. Average height 1675 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.