Plant propagation is one of those gardening terms that can be intimidating for some people but really it just means producing more plants from one parent plant. So taking cuttings, dividing and collecting seed to increase your stock of one particular plant. It’s enjoyable and it saves you money.
(a) Softwood Cuttings When: May-August
(Examples : Lavender, Forsythia, Fuchsia, Pelargoniums etc. perennials, houseplants)
-Usually taken in spring or summer. (Can be used to propagate tender plants such as bedding plants).
-Take cuttings of about 10cm (4in) in length, cutting below a leaf joint. (Shorter side shoots are taken with a ‘heel’, where the side shoot is pulled down and away from the parent shoot e.g Rosemary and Buddleia).
-Remove the bottom leaves from the lower third of the stem and insert into compost.
-Then place in a propagator (widely and quite cheaply available from online sources or garden centres when they re-open) to get them growing away. You can also try placing the pot into a clear plastic bag to act as a simple propagator.
(b) Semi-Ripe Cuttings When: July & August
(Examples: Argyranthemum, Camellia, Senecio maritima).
-These are taken in July and August when the plant’s growth is starting to slow down.
-Take cuttings from main stems or use strong, leafy non-flowering side shoots from the main stems. Cutting length should be about10-15cm (4-6in).
-Remove the lower leaves and dip the base in a hormone rooting powder. (Not essential but does help, again available online)
-Then insert about 2.5cm (1in) deep into small pots with compost. Either cover with a clear polythene bag or place in a covered propagator to get them rooting.
(c) Hardwood Cuttings When: Early Autumn
(Examples : Easiest way to make new plants from shrubs and trees)
-In early autumn, choose strong, straight shoots on this year’s growth.
-Cut just above a bud or pair of buds at the junction between the current season’s growth and the previous year’s growth.
-Remove any large leaves and side shoots from the stem and trim the cuttings to about 20cm (8in).
-Make an angled cut just above the top bud and a horizontal cut just below the bottom one.
-Insert the cuttings into a pot filled with compost and water it in well. Keep out of direct sunlight and with any luck the cuttings should be well rooted and ready for transplanting by the next autumn.
(d) Root Cuttings When: September-March
(Examples: Chaenomoles, Acanthus, Crambe, Dicentra, Eryngium)
-Take cuttings anytime between September and March.
-Use a sharp knife to cut off portions of root from the parent plant.
-Slice the roots into sections from 1cm to 7.5cm (0.5in to 3in) in length.
-Place root cuttings on a tray of moist compost and then cover with 1cm (0.5in) of compost.
-Once the shoots have emerged, lift the young plants from the compost and repot to grow them on.
(e) Leaf Cuttings
(Examples: Part Leaf Cuttings; Begonias, Streptocarpus, Sanseveiria)
Streptocarpus – cut the leaf in half along the midrib and then insert one half of the leaf, cut side down into damp compost and firm in.
Sansevieria – cut leaves horizontally into 5cm (2in) pieces and insert lower edge down into damp compost.
Begonia – cut across the main veins on the underside. Pin the leaf, cut side down onto the compost. Alternatively, cut the leaf into squares 2.5cm (1in) across each with a main vein. Water and then place in a propagator or a clear plastic bag in a light place out of direct sunlight . ‘Plantlets’ should form which can then be potted on.
2. Division When:Early Spring or Autumn
(Examples: Many perennials such as Delphinium, Heuchera, Stocks, Asters, Iris, Geraniums)
-In early spring or autumn, lift the plants, taking care not to damage the root ball.
-Divide each plant into several portions by gently pulling them away from the main plant by using 2 garden forks back to back (Hemerocallis) or splitting with a spade (Hellebores and Asters)
-Dig over the area that you want to put them back into and check over the divided plant for weed seedlings such as ground elder before you replant it.
-Firm in and then water it in well.
3. Layering When:Early Spring or Autumn
(Examples: Cornus, Magnolia Acer, Camellia, Chaenomeles, Cotinus, Daphne, Forsythia, Hamamelis, Jasminum, Magnolia, Rhododendron (including azalea), Syringa and Viburnum)
Layering is a way of encouraging part of the plant to grow new roots, rooting it on and then removing the new section from the parent. Its a clone of the old plant.
-Choose flexible young shoots on the outside of the plant that can be bent over to ground level.
-In either autumn or spring make a 2.5-5cm (1-2in) cut through a leaf node approximately 30cm (12in) from the shoot tip. This will encourage roots to form. Apply hormone rooting powder to the cut.
-Dig a shallow hole, 10-15cm (4-6in) deep and ‘peg’ the section to the ground, using metal pins or wire. Alternatively, sink a small pot containing Seed Compost and peg into that.
-Back fill with soil and firm around it. Water it in.
-After a year or so the layered area should have developed a root system and then can be cut off from the parent plant and transplanted to where its needed.
4. Collecting Seeds and Growing them on When: Once Seeds are Ripe
(Examples; Most Perennials, shrubs, trees)
-Often the easiest way to make new plants is to collect their seed after they have flowered and set seed.
-Seeds are usually collected only once they are ripe. (Signs of ripeness include splitting and opening of the seedpods or husks, and a darkening in colour of the seeds themselves).
-Choose a dry day for seed collection, so that the seeds do not become damp and
either rot off or start to germinate.
-Many hybridised plants will not come true to type from seed. Unlike with cuttings, where you get an exact clone of the parent plant, seedlings will be genetically different from their parents, and may have totally different flower colours or different levels of vigour.
-Cut off ripe looking seedpods, seed cases, fruits or cones from the parent plant.
-Remove any shrivelled or damaged looking seeds before storing.
-Many seeds are best stored dry, at fridge temperatures in paper bags so that they don’t sweat.
Sowing your collected seeds:
-Use specific seed compost for sowing in and water the compost before you sow into it. Sow thinly and not too deeply, roughly 1-2 times the size of the seed.
-Cover the seed lightly with compost and then cover the seed tray with a piece of glass and a sheet of newpaper until the seeds have germinated.
-Label the seedlings and make a note of the sowing date.
-When the seedlings have developed their first set of true leaves, carefully prick them out and transplant into a bigger pot.
-After potting on, it is important not to let the compost dry out. A hand held water sprayer can be useful for this.