Propagating Evergreen Ash From Cuttings, Air Layers and Seed

Pick the method that fits what you want

All three routes work. Cuttings give you several small plants from one pruning session and are the obvious thing to do with the material you have just cut off. Air layering gives you one substantial plant with a usable trunk in a single season, which is what you want if the aim is another indoor tree rather than a windowsill of seedlings. Seed is the easiest of all and the least useful, since it takes years to become anything.

Semi-ripe cuttings

Take cuttings from shoots that have firmed up but are not yet fully woody - the wood should bend and spring back rather than snap. Do this in the middle of the growing season, ideally from the material you remove during a shaping prune, and get them into compost within minutes of cutting.

1. Cut 5 to 6 inch (12 to 15 cm) pieces Cut just below a leaf node, with two or three leaf pairs above it. Remove the lower leaves entirely and halve the remaining leaflets to cut water loss.
2. Dip and insert Dip the base in rooting hormone, then push it a third of its length into a 50:50 mix of perlite and multi-purpose compost. Firm around the base so there is no air gap.
3. Keep humid and warm at the base Cover with a clear bag or propagator lid and stand on a heat mat at 70 to 75F (21 to 24C). Bright indirect light, never direct sun through the plastic.
4. Vent, then check for roots Open the cover for a few minutes daily to stop mold. From six weeks, tug gently: resistance means roots. Pot up individually once resistance is firm.

Expect to lose some. Take twice as many cuttings as you want plants, and throw out any that blacken at the base rather than trying to save them.

Air layering a thick stem

Air layering is the dependable option, and the right one if you want to shorten a tall, leggy tree and keep the top as a new plant instead of composting it. Choose a point on the stem where you would like the new plant's base to be, allowing for the fact that you will cut the stem off just below the roots when they form.

Ring the bark: make two cuts around the stem about an inch (2.5 cm) apart and peel off the bark between them, scraping the surface clean so it cannot bridge back over. Dust with rooting hormone, wrap the wound in a fist-sized ball of damp sphagnum moss, and seal it with clear plastic film taped tightly at both ends. Clear film matters - you need to see roots without unwrapping. When white roots fill the moss, cut the stem off just below the ball and pot it, moss and all, keeping it humid and shaded for a fortnight.

Seed, and the reason to be careful with it

Mature trees carry hanging clusters of winged seed that germinate readily in warm, damp conditions. Sown a quarter inch (5 mm) deep in moist compost at around 70F (21C), a fresh batch will come up in three to eight weeks with no special treatment. Prick the seedlings out at two true leaf pairs and grow them on in bright light.

That easy germination is precisely why the species has become a weedy escape in parts of the subtropics. If you have a fruiting tree outdoors in a mild climate, sweep up the fallen seed and bin it rather than composting it, and pull volunteer seedlings while they are small - a second-year seedling already has a taproot that fights back.

What to record

Log the date you took each batch, the method, the number started and the number that rooted. Two seasons of that tells you whether cuttings are worth your bench space or whether you should be air layering instead, and it pins down the point in your own growing season when strike rates are best.

For air layers, note the date you wrapped the moss and the date roots became visible through the film. That interval varies a lot with room temperature, and knowing yours stops you unwrapping too early and breaking the roots you were waiting for.