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Two methods do nearly all the work. Semi-ripe cuttings taken in the weeks after flowering give you many plants at once and are the standard approach for the evergreen kinds. Layering gives you one or two plants at a time with almost no skill and almost no failures, and it works on any plant with a branch low enough to reach the soil.
Timing for cuttings hangs on the state of the wood. You want this season's shoots that have gone from soft and floppy to slightly firm, bending under pressure and springing back rather than snapping. That stage usually arrives a few weeks after the flowers finish. Wood that is still soft rots before it roots; wood that is fully hard and woody roots very slowly if at all.
Seed is a third option but a poor one for a garden. Azalea seedlings vary widely from the parent plant and take several years to reach flowering size, so unless you are deliberately raising something new, take cuttings or layer instead.
| Method | When to start | Time to a plant | Reliability |
|---|---|---|---|
| Semi-ripe cuttings | A few weeks after flowering | Rooted in 6 to 12 weeks, potted up the next spring | Good with humidity and bottom heat |
| Simple layering | Any time in the growing season | Rooted by the following year | Very high, little can go wrong |
| Division | Not applicable | Not applicable | Azaleas form a single crown, not clumps |
| Seed | Autumn, sown on the surface | Several years to flowering | Seedlings differ from the parent |
Taking semi-ripe cuttings
Work in the morning while the shoots are full of water, and keep everything you cut in a sealed bag out of the sun until you get to the potting bench. An azalea cutting that wilts before it is inserted rarely recovers, because it has no roots to replenish what it loses.
Use a free-draining, acid, low-nutrient mix. Equal parts acidic potting mix and perlite, or a similar sharp mix, is right. Rich compost encourages rot around the cut end, and the cutting has all the food it needs inside itself until roots form. Rainwater rather than hard tap water for the initial watering keeps the mix acid from the start.
Humidity is the whole game. A cutting with no roots loses water through its leaves and must be kept in air close to saturation until roots take over. A clear bag over the pot, a propagator lid, or a covered tray all work. Bottom heat around 68F (20C) speeds rooting substantially, and shade is essential, since direct sun inside a covered container cooks cuttings within an hour.
- Cut healthy non-flowering shoots Take shoots three to four inches (8 to 10 cm) long from this season's growth, firm at the base but still flexible. Avoid shoots that carried flowers, which root less readily.
- Trim to a node and strip the lower leaves Cut cleanly just below a leaf joint and remove the leaves from the bottom half of the cutting. Leave three or four leaves at the top, halving any very large ones to cut water loss.
- Wound the base and dip in rooting hormone Scrape a shallow sliver of bark from one side of the base, about half an inch (1 cm) long, then dip in rooting hormone. The wound exposes the tissue that produces roots and noticeably lifts the strike rate.
- Insert into a gritty acid mix Equal parts acidic potting mix and perlite, in pots or a tray. Push each cutting in far enough to stand upright, space them so no leaves touch, and water in with rainwater.
- Cover and keep warm, bright and out of sun Enclose in a clear bag or propagator at around 68F (20C) in bright shade. Vent briefly every few days to change the air, and pick off any leaf that drops or goes moldy at once.
- Check for roots after six weeks Tug very gently. Resistance means roots. Start opening the cover a little more each day over two weeks to harden them, then pot up individually into acidic potting mix.
Overwinter first-year rooted cuttings under cover in a cold frame or an unheated greenhouse. The root system is tiny relative to the top growth and a hard frost or a drying winter wind will kill plants that rooted perfectly well.
Layering, the method that rarely fails
Layering roots a branch while it is still attached to and fed by the parent plant, which removes every reason cuttings fail. Choose a flexible low branch that can be bent down to touch the soil about eight to twelve inches (20 to 30 cm) back from its tip. Loosen the soil where it will lie and work in some acidic potting mix or leaf mold.
Wound the underside of the branch where it will meet the ground, either a shallow slanting cut part way through or a sliver of bark scraped off, and dust it with rooting hormone. Pin the wounded section down with a stout wire staple or a stone, bury it two to three inches (5 to 8 cm) deep, and tie the leafy tip to a short cane so it is held upright.
Then leave it. Keep the spot damp through the growing season and check the following year by scraping the soil back gently. When there is a decent mat of roots, cut the branch from the parent on the parent side of the rooted section, leave it in place for a few more weeks to adjust, then lift and plant it out.
Keeping track of what you propagated
Label every batch at the moment you insert it, with the date taken and which plant it came from. Rooted azalea cuttings look identical to one another for their first two or three years, and unlabelled trays become an anonymous collection of small green shrubs whose flower color is a surprise.
Note the date you took the cuttings against the date flowering finished on the parent, because that gap is the number that matters and it shifts a little each year with the weather. After two seasons of records you will know your own timing far more precisely than any general advice, and your strike rate will show it.