Layering: Plant Propagation

Provided that time is of no particular concern -the process can take anything from six weeks to two years – then layering is perhaps the best and surest means of plant propagation. The great advantage of the system over cuttings is that throughout the period when the new plant is developing roots, it is still part of the parent plant and is receiving nourishment from it. Not until the root system is fully grown is the offspring severed from the parent plant, consequently, the failure rate is very low indeed.

There are five layering methods, used for differ­ent types of plants and in different circumstances. Four of the methods involve taking stems to the ground and rooting them there. In the fifth method, air layering, the soil, in effect, is taken to the stem.

SIMPLE LAYERING

Used to propagate many shrubs, especially those with low-growing stems, and some perennials, such as carnations. Some shrubs – rhododendrons and magnolias, for example – reproduce naturally by layering their branches in this way.
– At some time between April and August, choose a low-growing, flexible stem, no older than last year’s growth and preferably this year’s.
– About 12in back from the tip. make a Thin long cut in the bottom side of the stem and insert a matchstick to hold the wound open. Dust the cut with a hormone rooting powder.
– Make a hole about 6in deep and peg the cut part of the stem into the bottom of the hole. Use a bent piece of wire or a couple of twigs for the pegs. Pill the hole with a mixture of one-third each by volume of peat, soil and coarse sand.
– Stake the tip of the layered stem to give it stability.
– About 12 months later (six weeks for carnations), gently scrape the soil away to see if new roots have developed. If they have, sever the stem from the parent plant, replant it in its new and permanent site and water it thoroughly. If. on the other hand, no roots are yet showing, replace the soil, leave the whole thing for a few more months and try again.

TIP LAYERING

This follows much the same principles as simple layering, except that the tip of the stem is cut. pegged and buried rather than the middle, so that the new plant grows from the bud at the end of the stem. Carried out in July or August, tip layering is the best way to propagate cane fruits such as blackberries and loganberries.

SERPENTINE LAYERING

Like simple layering, serpentine layering should be done between April and August. It is most often used to propagate such climbers as clematis, honeysuckle, jasmine or wisteria.
– Select a long, trailing, many-jointed shoot of this or last year’s growth.
– Make cuts not more than halfway through the stem at the leaf joints, cutting as many joints as the number of plants you wish to propagate.
– Dust the cut joints with rooting powder and peg and plant each of them in the same way as for simple layering – leaving a series of low hoops visible above ground, rather like the traditional image of the Loch Ness Monster.
– Stake the tip of the stem to prevent disturb ance of the rooting leaf joints.
– About a year later, scrape away the soil to see if the joints have rooted. If they have, sever them from the parent stem, and from each other, and replant them in their permanent site. If they haven’t rooted, put the soil back and leave them for a few more months.

RUNNER LAYERING

The classic method of propagating strawberry plants, which also applies to spider plants (Chhrophytum conwsum) and mother-of-thousands (Saxifraga stolonifera). All these plants send out runners which develop small plants along their lengths and at the tips.
– In June, peg the young plants, still attached to the parent, into pots of potting compost.
– In August, or at the latest in September, sever the plants from the parent and transplant them into their permanent site.

AIR LAYERING

This very different method is used to propagate trees or shrubs whose stems arc too stiff or too high to be easily bent to the ground.
– In March or April, select a one or two-year- old stem and strip the mid-part of its leaves.
– About 12in from the tip. make a shallow, slanting cut, dust it with hormone rooting powder, and pack it with sphagnum moss,
– Pull an 8- lOin sleeve of transparent polythene over the stem and firmly tie the bottom end in about 3in below the cut.
– Pack the sleeve with a mixture of 2 parts sphagnum moss, and 1 part each of peat and coarse sand by volume. Thoroughly wet the mix ture and tie in the top end of the sleeve to the stem. The joints must be airtight to prevent the mixture from drying out.
– Support the stem against the extra weight by tying it to a cane or to an adjacent branch.
– When roots are visible through the polythene, which can take a year or more, cut the stem off just below the plastic, take off the plastic and pot up the new plant in its growing mixture. Harden the new plant off before transferring it to its permanent position.