Plant Propagation by Taking Cuttings
Plant Propagation – Taking Cuttings
A cutting is a portion of stem, root or even a leaf of a plant, without roots, that, given the right conditions, will send out roots and form a new plant. An ‘Irishman’s cutting’ denotes a shoot that has a little piece of root already attached. In Ireland, cuttings are often called ‘slips’.
Many plants — shrubs and tenderin particular — root easily in late summer and early autumn. At this time of year there is sufficient warmth in the sun to encourage the cuttings to form roots, but it is not so hot that they wilt too often, eventually give up and die. While these plants will still root in mid-autumn and even later, their root formation becomes slower as winter advances.
Peat has been widely used in horticulture for several decades. While its use is no longer universally acceptable, there is no doubt that, mixed with horticultural sand, makes a suitable compost for rooting cuttings. In areas where peat is still harvested at a sustainable level, that is, in a quantity equal to the rate of natural renewal, you can mix up your own cuttings compost using two parts of moist peat to one part of horticultural sand. Research into different peat substitutes is still under way and various multi-purpose composts on the market are recommended as suitable for rooting cuttings. In this section, the term ‘cuttings compost’ means either a proprietory compost specially formulated for cuttings or your home-made peat and sand mix.
Rooting the cuttings
What you do with your cuttings depends on your generalarrangements. You can use either a heated , a shaded cold frame with the lights closed, or an old-fashioned bell-jar in the corner of a : all prevent the cuttings losing moisture long enough for them to form roots. The cuttings should be kept in a warm place, out of direct sun. Keep a hand-sprayer full of water nearby and mist over their foliage on hot days. You can also make a sort of mini-greenhouse by placing a small stick in the middle of the pot, putting the whole thing in a polythene bag and tying the mouth of the bag tightly to the stick.
As soon as you think the cuttings are rooted (you will see signs of new growth or roots coming through the holes in the bottom of the pot), you can gradually give them more air. You can then pot them individually into small pots and keep them in a frost-free greenhouse for the winter.
Some of the plants in the list will only survive outdoors in mild climates. By taking cuttings and keeping them under glass for the winter you will have fine plants the following spring. Silver-leaved plants, Mediterranean plants in general and Pelargonium are some of the plants whose cuttings do not like the enclosed, humid conditions of a propagator or polythene bag and prefer the shady part of a greenhouse or kitchen window sill, out of full sun.
In late summer or early autumn choose a healthy-looking shoot as described below. With many of the plants listed (right), it should be possible to find a suitable cutting with a heel, but if you cannot find a suitable ‘heeled’ cutting, trim your chosen piece of stem immediately below a pair of leaves. Try and find a leafy shoot with no flowers — or, if there are any flower buds, cut them off, as they will only attract mould and use up the strength of the cutting.
As soon as a cutting is removed from a plant, its first inclination is to wilt, so put it straight into a polythene bag until you are ready to deal with it. Remove one or two pairs of leaves from the bottom of the stalk. If, from where you pulled off the cutting from the parent plant, the heel of older wood has a straggly piece of tissue attached, trim it off cleanly with a sharp knife. Fill a 9cm (3-1/2in) pot with cuttings compost — you are not being kind by using a larger pot, only encouraging the second inclination of the cutting, which is to rot at the base. Insert the cuttings (about six per pot) firmly around the edge. Water, using a fine rose on the watering can so as not to flood the pot.
This method may be used for many, including , Eryngium, Echinops, Romneya, Verbascum, Phlox, Papaver orientale, Limonium, Primula denticulata and Crambe. The cuttings are usually taken in late winter. Dig away the soil to get at the roots. You can then cut thick roots into sections, with a straight cut at the top and a sloping cut at the bottom (this is to remind you to insert it the correct way up). Insert the cuttings vertically in a pot of cuttings compost and place them in a cold, frame or greenhouse. Smaller roots, of plants such as Phlox, are placed horizontally on the surface of the compost and covered with sand.
This method is not much used in the flower garden except for increasing Ramonda and Haberlea. Take a healthy leaf (not one of the damaged outer ones) with its leaf stalk still attached, from near the centre of the plant, around mid-summer. At the base of the leaf stalk you should see the faintest sign of a bud — it is this that will form the new plant. Insert the cuttings firmly in a pot of cuttings compost, then water and place in a shaded cold frame. Do not disturb until the following spring, when you should see nice little plants forming at the base of each leaf.
Short, basal or tip cuttings of the young growing shoots of many herbaceous plants (such as, cultivars of Gentiana asclepiadea, Lythrum, Nepeta and Sedum) can be taken in spring. Dendranthema (once called Chrysanthemum) are usually propagated this way, but the hardy pompons such as ‘Mei-kyo’ can also be propagated by division. The soft shoots are inserted round the edge of an 8cm (3in) pot of cuttings compost. Water and place the pot in a cold frame or cool greenhouse. New shoots of Fuchsia root well in spring in warmth.
In the flower garden this is a useful method of propagating roses. In mid-autumn, take 23-30cm (9-12in) long cuttings of firm healthy wood, with a heel; remove the leaves. In a sheltered part ofinsert the cuttings in a small trench with some horticultural sand in the bottom. Make them very firm and do not disturb them for a year. Rose cuttings can also be rooted in warmth in summer, using young shoots about 10cm (4in) long. Often the only way to obtain some beautiful but nameless rose is by rooting it from a cutting, and roses grown this way, on their own roots, will never trouble you with suckers. Most make good plants propagated by this method, but large-flowered and cluster-flowered roses are best bought as budded plants.
Taking cuttings outside
Some plants root easily in the open garden. Violas such ascornuta can be divided but some of the cultivars, for example Viola ‘Irish Molly’ and Viola ‘Jackanapes’ need to be propagated from cuttings. Choose a light position, but out of the sun. Make a little trench about 15cm (6in) deep with a trowel, fill it up with cuttings compost and firm it well before making any holes.
Choose 5cm (2in) chubby young non-flowering shoots from the centre of the plant (the straggly, long flowering shoots will not root). Pull them off with a little tug, rather than cutting them. If the cuttings are too long, trim them to below a pair of leaves. Take off one or two pairs of the lower leaves of the cutting, being careful not to tear the stem. Make a hole in the cuttings mixture and, being careful that the base of each cutting is fully in contact with the bottom of the hole, insert the cuttings in a row. The cuttings will be in intensive care for the next week or two: this means that you should give them a sprinkle of water from the can several times on warm days. Violas are hardy and can stay where they are until the following spring.
Cuttings of pinks () dislike too-warm conditions for rooting, and also prefer being outside. In summer, select non-flowering side-shoots, known as ‘piping’s, about 8cm (3in) long and treat them in exactly the same way.