Propagating Black Locust (Robinia pseudoacacia) from Stem Cuttings

Overview

Black locust (Robinia pseudoacacia) spreads aggressively through root suckers, forming interconnected groves. While this makes it nearly weed-like in some regions, gardeners seeking genetically identical clones of a parent tree must use vegetative propagation since seed-grown trees exhibit significant genetic variation. Stem cuttings can be challenging to root but offer the only reliable method for clonal reproduction.

Step-by-Step Stem Cutting Propagation

Step 1: Select and Prepare Cuttings

In early summer, cut 8+ inch sections of new growth with a leaf node near the base. Longer cuttings are acceptable.

Step 2: Apply Rooting Hormone

Dip the basal end in rooting hormone powder, ensuring good coverage. This significantly improves rooting success for this difficult-to-root species.

Step 3: Plant in Rooting Medium

Insert cuttings into a 50/50 sand-vermiculite mixture. Water thoroughly and maintain temperatures of 70-75°F (21-24°C).

Step 4: Maintain High Humidity

Mist cuttings frequently with a spray bottle and keep the medium consistently damp but not waterlogged.

Step 5: Exercise Patience

Rooting can take three months or longer. Resist the urge to tug cuttings to check for roots; wait for visible new growth as confirmation.