Osteospermum Cuttings: Rooting Shoots in Late Summer for Next Year

Why cuttings beat keeping the parent plant

Gardeners who want their African daisies again next year usually try to overwinter the whole plant, and it is the harder route by a long way. A mature osteospermum is a woody, spreading thing that needs a large pot and a bright frost-free space, it holds a lot of damp foliage that invites rot and whitefly under cover, and even when it survives it emerges in spring as a leggy second-year plant that needs cutting back hard before it will flower properly. A tray of rooted cuttings takes a fraction of the space, comes through the winter far more reliably, and gives you young plants that flower like first-year ones, because that is what they are.

Take them in late summer, while the weather is still warm and the plant is producing plenty of firm new shoots after its mid-season cut. Cuttings taken then root fast, in about two to three weeks, and have time to make a proper root system and a few new leaves before the cold arrives. Wait until autumn is well under way and you get slow rooting, soft growth going into winter, and heavy losses.

Take far more than you think you need. Cuttings are free and losses over winter are normal. Eight to twelve rooted plants from a parent you were going to discard anyway is a good return, and any surplus makes obvious gifts.

Some named ornamental plants are protected by plant breeders' rights, which restricts propagating them for sale. Rooting cuttings for your own garden is fine; check the label before you propagate anything to sell or trade in quantity.

Choosing and taking the material

The right cutting is a non-flowering shoot tip, three to four inches (8 to 10 cm) long, that is firm rather than either soft and floppy or hard and woody. Bend one: it should have some spring to it and snap cleanly rather than bending limply or resisting like a twig. Shoots pushed out after a mid-season shear are close to ideal, which is one more reason to do that cut.

Avoid anything in flower or in bud. A cutting carrying a bud spends its energy on the flower instead of making roots, and it is the first one to rot in the propagator. If the only material available has buds, pinch them out before you insert the cutting. Avoid anything with aphid damage, mildew blotches or distorted growth, because you will carry the problem straight into your new plants.

Work in the morning when the parent is fully turgid, use a clean sharp blade rather than scissors which crush the stem, and keep the cuttings in a closed bag out of the sun until you get them into compost. Ten minutes lying on a warm bench is enough to lose a batch. Prepare the pots and mix before you cut anything.

Rooting them, step by step

The whole operation takes about twenty minutes and needs no equipment beyond a pot, a gritty mix and a clear bag. Success rates well above half are normal, and often much higher if the material is right.

1. Mix a gritty rooting medium Use roughly half all-purpose potting mix and half perlite, coarse sand or vermiculite by volume. It must be open enough that water runs straight through. Ordinary potting mix on its own stays too wet and rots the stem bases.
2. Cut just below a leaf joint Trim each shoot to three to four inches (8 to 10 cm), cutting cleanly immediately below a node. Roots form most readily at the node, so a cutting with a long bare stem below the lowest node will root slowly if at all.
3. Strip the lower leaves Remove all leaves from the bottom half to two-thirds of the cutting, leaving two to four leaves at the top. Any leaf buried in the compost will rot. If the remaining leaves are large, cut them in half across to reduce water loss.
4. Dip in rooting hormone if you have it Dip the cut end in hormone rooting powder or gel and tap off the excess. It is not essential for osteospermum, which roots readily, but it speeds things up and gives a more even batch.
5. Insert around the edge of the pot Make holes with a pencil or dibber rather than pushing the stems in, which strips the hormone off. Set them about an inch (2.5 cm) deep, around the rim of a pot where drainage is best, spaced so no leaves touch. Five or six to a five-inch (13 cm) pot.
6. Water once, then cover loosely Water thoroughly to settle the mix and let it drain fully. Cover with a clear bag held off the leaves with canes, or use a propagator lid with the vent open. The cover must not touch the foliage and must not be sealed airtight.
7. Keep warm, bright and out of direct sun Aim for 65 to 70F (18 to 21C) in bright indirect light. Direct sun under a bag cooks the cuttings within an hour. Air the cover for a few minutes daily to let condensation off and mist only if the mix is drying.
8. Check for roots after two weeks Tug very gently. Resistance means roots. New growth at the tip is the other reliable sign. Once rooted, remove the cover over a few days, then pot each one individually into a three or four inch (8 to 10 cm) pot of ordinary free-draining compost.

Getting the young plants through winter

Rooted cuttings need a bright, frost-free, airy place: a cool windowsill, an unheated but protected porch, a frost-free greenhouse or a cold frame in a mild area. Around 40 to 50F (5 to 10C) is ideal. Warm rooms are the wrong answer, because warmth plus low winter light produces long pale weak growth that collapses at the first setback and is a magnet for whitefly.

Water very sparingly through the darkest months. The mix should be barely moist and the surface should dry between waterings. More overwintered osteospermum cuttings are killed by watering than by cold. Do not feed at all until growth restarts in late winter, and then only weakly.

Check them over every week or two. Pick off yellowing leaves, look under the top leaves for whitefly, and give the plants space so air moves between them. If a cutting goes soft and black at the base, remove it and its compost immediately, because rot spreads through a crowded tray fast. As light returns in late winter, growth restarts. Pinch the tips out to force branching, pot up into slightly larger pots if roots are showing at the drainage holes, and start hardening off once the frosts are finished. These plants will flower earlier and harder than anything you buy.

Seed, and what to record

You can raise osteospermum from seed and it germinates readily at around 65 to 70F (18 to 21C), sown under cover about eight to ten weeks before you intend to plant out, barely covered because it needs some light. What you cannot do is expect seedlings to match the parent. Seed saved from a garden plant produces a mixed batch of variable height, habit and flower color, and a proportion of them will be plain and disappointing. Cuttings give you exactly the plant you already have; seed is an experiment.

Record the date you took cuttings, how many you took, and how many were rooted and potted three weeks later. Then record how many were still alive at the end of winter. Those three numbers, kept for two seasons, tell you your own strike rate and how many cuttings you actually need to take to get the number of plants you want, which is usually more than people assume.

Note the conditions too: where the cuttings sat, roughly what temperature, and how often you watered them over winter. When a batch fails, the difference between that batch and a successful one is almost always in those notes, and almost always about water.