Propagation by cuttings

A simple way to propagate most shrubs and many perennials, including house plants, is to take stem, tip, leaf or root cuttings.

Propagating by cuttings involves removing a section of living stem, root, leaf or bud and planting it in conditions that encourage roots to form. For a cutting to strike (take root) it needs adequate light, warmth and moisture. Very small cuttings are liable to exhaust food reserves before forming roots; overlarge cuttings draw up too much water and soon flag. The potting com-post needs to be free-draining, and yet capable of retaining sufficient moisture, and it must allow the free passage of air. It also has to be free of pests and diseases.

Softwood tip cuttings

Perennials such as Centaurea gym-nocarpa, penstemon and dimor-photheca, and sub-shrubs such as Helicbrysum petiolate and rue (Rata) are best grown from tip cuttings. Take these cuttings from non-flowering lateral shoots in late summer and early autumn, and protect in a cold frame over winter. Take tip cuttings of pelargoniums, marguerites and fuchsias in early spring, late summer or autumn.

Take 7.5-10cm (3-4in) cuttings from healthy, leafy stems, ensuring that each has at least three leaf joints. Fill a pot to just below the rim with peat-based seed and cutting compost. A 10cm (4in) pot takes about six cuttings.

Trim each cutting to just below the lowest leaf node, using a sharp knife or razor blade. Remove the lowest pair of leaves. Make shallow planting holes with a pencil, or dibber. Insert the cuttings so that the base of each stem touches the bottom of the hole, without burying the leaves, then firm in with your fingers.

Water lightly, label and cover the pot with a plastic bag, secured with a rubber band. To prevent the plastic touching the cuttings, construct a framework of sticks or looped galvanized wires before putting the plastic in place. (Pelargoniums root best left un-covered.) Set in a shady cold frame to root or in a propagating frame heated to 16°C (61°F).

After three to six weeks the cuttings should have rooted. Check by tugging them gently. Remove the plastic covering or take the pots out of the propagator. Leave cuttings in a frame for a few days, then remove from the pot by turning it upside down and dislodging the potting compost in one piece.

Separate the rooted cuttings carefully, then pot up singly into 7.5cm (3in) pots of peat-based or John Innes No l potting compost. Firm in then water thoroughly, allow to drain, then place in a shaded cold frame. Pinch out the growing tip of each plant after about a week to encourage side shoots and a strong root system.

Overwinter in a closed cold frame. Plant out in their growing positions in spring, when the risk of frost is over.

Semi-hardwood cuttings

Many shrubs and trees, including actinidia vines, spotted laurel (Aucuba), lavender (Lavandula) and Mexican orange (Choisya) can be propagated from semi- hardwood cuttings, taken from mid to late summer from the cur-rent year’s growth.

Choose moderately firm and woody shoots but with soft tips. These cuttings need attention from the time they are set out until they are rooted. They will need to be kept in a propagating frame, watered when necessary, and shaded from the sun. It will take a year or two before they are ready for their permanent quarters.

With a knife or secateurs, cut off a 15-20cm (6-8in) side shoot close to the main stem. Remove the lower leaves and sever just below the lowest leaf node. Trim the soft tip above a leaf so the cutting is 5-10cm (2-4in). Cuttings often root more reliably if removed with a sliver of the parent stem.

SOFTWOOD TIP CUTTINGS

Place potting compost in the bottom of a 9cm (31.5in) pot. Stand the young plant on this and then fill the pot with compost to just below the lowest pair of leaves. Firm the compost so that the surface is about 1 cm (0.5 in) below the rim, then water generously.

Keep the pot in a greenhouse or frame and never allow the compost to dry out. In three weeks, the roots should have reached the outside of the compost. Pot on into a larger pot and place in an open cold frame.

Keep those that are not fully hardy in a frost-free frame or greenhouse for the winter. Plant out in spring.

Plants such as pyracantha and Californian lilac (Ceanotbus) are unlikely to root without this heellike sliver, which contains growth hormones that assist rooting.

First, cut off the branch carrying several side shoots, preferably without flowers. With a sharp knife, make a slanting cut into the branch beneath the junction with the side shoot, then cut in the opposite direction to remove a 5-7.5cm (2-3in) long shoot. If longer, trim from the tip; take a few extra cuttings to allow for losses. Fill a pot to just below the rim with a proprietary cutting compost. A 7.5cm (3in) pot will take up to five cuttings, a 13cm (5in) pot up to ten.

Make a hole in the compost, about onethird the length of the cutting. Insert each cutting and firm it, then water generously with a sprayer or a watering can with a fine rose.

The cuttings need a humid at-mosphere so they do not dry out. One way is to make a cover from galvanized wire and a polythene bag, as before, or place in a pro-prietary plastic propagating case. Use a box for a large number of cuttings, covered with a polythene and wire frame.

Improve rooting conditions by providing heat from underneath so the bases of the cuttings stay slightly warmer than their tops. You can do this by placing the container over heating pipes in a greenhouse, or use electric soil-warming cables. Some propagating frames are heated. Most hardy plants need the compost kept at 16-18°C (61-64°F). Cuttings generally root without bottom heat, but may take longer to do so.

After rooting, acclimatize the cuttings to drier or colder conditions by ra18 ing the polythene, or piercing a few holes in it, to let in air. Protect them from strong light. One week later, raise the polythene still higher or make more holes in it. A week after this, remove the polythene altogether. By the following week the cuttings are ready for potting singly.

Gently remove cuttings from the pot or box and tease them apart.

Hardwood cuttings

The simplest way to propagatemost hardy shrubs and trees is to take hardwood cuttings from mid autumn to late winter. Except for watering in dry spells, and weeding, no further attention is needed for 12 months. The young shrubs or trees are then ready for planti-ng in their permanent quarters.

Hardwood cuttings are vigorous stems which have just completed their final season’s growth and have become hard and woody. They bear buds all along their length which will grow into new shoots the following spring.

Take the cuttings in mid au-tumn, when they have just stopped growing and are beginning the winter period of dormancy, though some shrubs will grow from hardwood cuttings taken any time in late autumn or winter.

Use secateurs to cut the stem near its base and then trim to 25-30cm (l()-12in). If the shoot is a long one, two or more cuttings may be made from it. Avoid using the soft thin tips, as this will produce a weaker plant or may not root at all.

Sever each cutting cleanly just below a bud or joint at the base, and just above a bud at the top end. Cut evergreens below and above a leaf and remove all the leaves on the lower half.

With large-leaved plants, such as cherry laurel (Prunus lauro-cerasus), you should reduce each leaf by half its surface area, using a razor blade or sharp scissors. This reduces water loss until the cutting has rooted.

Shrubs that are difficult to root often respond to the technique of wounding – removing a thin sliver of bark near the base of the cutting – then dipping the base in rooting powder, making sure to cover the wounded area.

Choose a site sheltered from north and east winds and dig it thoroughly. Work coarse sand into heavy soil to help drainage and aeration. Make a narrow slitlike trench by pushing in a spade to full blade depth and pulling it forward for several centimetres (inches). Place a 2.5-5cm (l-2in) layer of coarse sand in the bottom, and stand the cuttings on it so that the lower half or twothirds is below ground. Plant 7.5-10cm (3-4in) apart with 60cm (2ft) between rows. Push soil into the trench and firm with your foot.

If cuttings come loose after severe frosts, re-firm them so the base is again in contact with the soil. In early spring, firm again. Hoe regularly in summer, and water during long, dry spells. After a year, most of the cuttings will be ready for lifting and setting in their permanent quarters. Leave slow-rooting or -growing species in situ for another year.

Suckers

Some trees and shrubs produce rooted shoots or suckers below ground. These are ideal for instant propagation and are, in effect, ready-rooted cuttings. Between mid autumn and early spring remove soil from the base of the sucker to check that roots have formed.

Cut the sucker close to its point of origin – a stem or root – and lift. (Plants to be propagated by suckers must be growing on their own roots – suckers from grafted plants, such as roses, witch hazels, rhododendrons and viburnums, are not suitable as they will only reproduce the rootstock.)

Plant well-rooted specimens directly in their permanent sites, and poorly rooted ones in a nursery row or spare corner of the garden to grow on. Increase plants such as strawberries from runners – surface stems which grow from the crown. Separate the plantlets which develop at their tips.

Leaf-bud cuttings

If you need several new shrubs from a limited amount of propagating material, take leaf-bud cuttings. Provided they are taken at the right time individual buds can root more quickly than those on a traditional cutting. Camellias are propagated by this method.

In late summer or early autumn, take cuttings from semi-hard lateral shoots (those which began growing in the spring) with several leaves and a growth bud in each leaf axil. With secateurs, cut off the shoot near its base. Then with a sharp knife, cut through the shoot at an angle, about 2cm (/tin) below the lowest leaf.

Sever the shoot just above the bud in the leaf axil, cutting straight across. Three or four leaf-bud cuttings can be made in this way. Scrape some bark off the cutting with a knife, then dip the end and the wounded part of the cutting in rooting powder.

Fill a pot to just below the rim with a proprietary cutting compost. Take about 12 cuttings for each 15-18cm (6-7in) pot.

With camellias, the leaf-bud cur-ting should contain only a small bud with a leaf and a sliver of wood attached – the sliver being scooped out of the parent stem with a sharp knife. Insert in the compost so that only the leaf shows on the surface.

Water lightly after insertion. Use a small hand sprayer, or shake water on with your fingers. Cover the pot with a wire and polythene hood to provide a humid atmosphere, then place in the greenhouse or cold frame.

Six months later, knock out the rooted cuttings from the pot and gently separate them. Place potting compost in 9cm (3’/in) pots – one for each pot.

Plant the rooted cutting centrally and top up with compost so that it is covered to just below the original leaf. Firm the compost so that the surface is about 1.5cm (Vi’in) below the rim, to allow for watering. Water in generously and keep in a greenhouse or frame. Never let the compost dry out.

In three to six weeks, the roots should reach the bottom of the compost. Hardy species can now be planted out in the open. Less hardy ones should go into a larger pot in the greenhouse, or a frame, for the following summer and winter before being planted out.

Basal cuttings

Most clump-forming perennials, such as bugloss (Anchusa), thrift (Armeria), scabious (Scabiosa) and delphiniums can be propagated by lifting and dividing an existing rootstock, usually when dormant, into several smaller pieces, each with a growth bud. However, cuttings can also be taken from the young shoots of the above plants, and from lupins, which appear from the base in spring.

Cut off basal shoots when they are 7.5-10cm (3-4in) long, at crown level or just below. Insert the cuttings directly into loamy soil in a cold frame, or in 7.5cm (3in) pots containing equal parts of peat and sand or a proprietary cutting compost.

Keep cuttings well watered by regularly spraying them from above, and keep the frame closed. As new growth starts to show, gradually open the frame to increase the ventilation. After about six weeks, pot the cuttings singly in 9cm (3’/2in) pots of John Inncs No 1 potting compost. Plant out in their final positions in autumn.

Root cuttings

Some herbaceous and woody plants naturally produce shoots direct from their roots, particularly where damaged. Consequently, pieces of severed root can be used as cuttings. Suitable shrubs include sumach (Rhus), smoke bush (Cotimts) and aralia.

Any time from autumn to spring, unearth part of the root system then, with secateurs, cut off thicker roots close to the main stem. Using a knife, cut into pieces about 4cm (lViin) long. Cut each piece straight across the top (nearest to the main stem), and at an angle at the base, to show you which way up to plant them. With thick or fleshy-stemmed perennials, such as bleeding heart (Dicentra) and California tree poppy (Romneya), make 5-7.5cm (2-3in) cuttings.

Fill a pot to just below the rim with a cuttings compost. Make holes to the same depth as the cuttings using a pencil. Insert the cuttings, flat-top uppermost, so the top is flush with the surface. Put six cuttings into each 12cm (5in) pot. Cover with 6mm of coarse sand, then water lightly.

Cuttings taken from thin-rooted perennials, such as phlox and verbascum, must be 5-7.5cm (2-3in) long and planted horizontally about 1cm (0.5 in) deep. Keep in a greenhouse or frame. Six months later, knock out the rooted cuttings from their pot and gently separate them. Pot up and care as for semi-hardwood cuttings.

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