Root cuttings

of the plant, at right angles to the root. Return the parent plant to the garden.

Discard the thin root end by slicing with a sloping cut. Slice off any fibrous lateral roots on the cutting to ease handling and planting later on.

The removal of roots from the parent plant for propagation will have had the additional effect of root pruning and so will cause the development of further roots for propagation in the ensuing propagating season.

Size of a root cutting

The size of a root cutting may not be critical if only one cutting is made from each root, but, with roots that regenerate readily and from which it is possible to make more than one cutting, the optimum size of a root cutting becomes very important. It is therefore necessary to determine the minimum size for a root cutting so that maximum use can be made of the available root.

The size of the root cutting depends on two factors. Firstly, the cutting requires sufficient food to initiate and develop a stem bud to the stage at which it produces green

Obtaining cutting material leaves and can begin to support itself. Secondly, the cutting requires suffic ient food reserves to support itself while this regenerative process is going on.

The size of the cutting, therefore, is made up of the regenerative portion and the survival portion. The size of the survival portion depends on how long the cutting will take to regenerate, and this is reliant on the temperature in which the cutting is propagated: the warmer the environment the quicker the stem will develop. A root cutting taken and planted in the open ground during the winter may not produce a shoot until May, but if it had been placed in a propagator in a temperature of 18°-240C/65°-750F, it might well have regenerated in about four weeks. The amount of food reserve required for survival between these two temperature environments is dramatically different.

The size of the regenerative portion needed, however, will remain constant whatever the temperature of the propagating environment, so a rule of thumb measurement for the size of a root cutting is based on the variable factor—temperature.

Root Cuttings Guide

7 Lift the plant in the middle of the dormant season. Cut any top growth.

8 Wash its roots. Then cut off the young roots close to the crown and set aside.

9 Return the plant to its usual position in the garden.

As a plant's roots will have been pruned a year before the cuttings are taken, all roots will show one year's growth and therefore be approximately the same thickness. Thus the cutting length is unaffected.

An open-ground cutting should be at least 4 in long as it will need to survive for some 16 weeks. A cold frame/cold greenhouse provides a warmer environment, and regeneration will occur in about eight weeks and so a smaller survival portion is required and the cuttings need only be just over 2 in long. In a warm (180-24°C/650-75°F) greenhouse or propagator, regeneration time is reduced to four weeks, halving the survival time and the required food reserve once again so that in this environment root cuttings need only be about 1 in long.

Recognizing the top of a root cutting

When propagating plants from root cuttings it is very important to notice the "polarity" of the cutting—that it has a top and a bottom and therefore a "right way up". Most people suggest that root cuttings should be planted horizontally because the cuttings have been

Taking a root cutting made in such a way that the top and bottom cannot be recognized, and there is no other way in which polarity can be recognized because roots have no leaves and axillary buds. However, stem cuttings are not planted on their side, so it is unreasonable to expect root cuttings to be, no matter in what direction their roots subsequently grow. Cuttings planted vertically and the correct way up will usually develop to a maximum level provided that the cuttings were taken from a healthy plant and they were given suitable conditions (see page 40). Cuttings planted on their side rarely achieve more than a 40 per cent success rate.

In order to recognize the top of a root (that is, the end nearest the crown of the plant) so it can be planted the right way up, make a flat cut at right angles to the root where it was severed from its parent; at the bottom end cut away the thin portion using a sloping cut. Always cut roots in this way so, whatever subsequently happens to the root cutting, it will be possible to recognize its correct polarity and so ensure that it is planted the right way up.

Polarity Cuttings

. 10 Cut off any fibrous lateral roots on undamaged young roots.

11 Make a right-angled cut on a root where it was severed from its parent.

12 Cut away the thin root end at the appropriate length, using a sloping cut.

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