Grafting red hawthorn

It’s about eleven years since I was on the search for red flowering hawthorn

(Crataegus oxyacantha). Most of the trees I found, though, were unsuitable as bonsai because they had a poor root base, and only high branches on the trunk, which also had no movement in it — not a favourable scenario. So I decided to grow them myself, just the way I wanted

Because of my education in horticulture, I had some knowledge of the art of grafting. First of all I graft-

ed with red flowering hawthorn but, later on, I grafted on other deciduous and coniferous species, too. By experimenting and learning from experts, I managed to improve my technique. I will show you how I graft with hawthorns.

Grafting is to place a freshly cut part of a plant in bud (the scion) directly on to a freshly cut trunk with a root ball (rootstock). The aim is to encourage both to grow together as a single plant. There are different methods of grafting for deciduous trees, but the main goal is that you have a rootstock and a matching scion. The method demonstrated here is the one I use for grafting hawthorn, but it can be implemented for almost any deciduous tree.

Why graft?

Grafting is used when plants grown from seed take too long to mature, don’t blossom in a reasonable time, nor grow true to type. Pine, beech, or red hawthorn is difficult to propagate from cuttings. Some plant varieties simply don’t have strong roots, so they are grafted on to stock that posseses this quality.

Natural response to a cut or wound

With grafting, we make use of the healing ability of plants. The so-called Cambium layer helps to heal over cuts or other wounds. The Cambium is a one-cell layer that generates new tissue to transport liquids, for growth in girth and is situated between the sapwood, phloem and bark layers. Transportation of water and nutritious salts are to be found in the sapwood layer. In the phloem layer the nutritives produced by the leaves circulate downwards. When you graft, both the scion and the rootstock will develop cells that have a corky texture, called Callus. Under the influence of the Cambium layer the callus cells will grow over the bare face of the wound.

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The healing is a gradual process, the rate being directly related to the health and growth of the tree. You can

Obtaining fresh scions

Scions are obtained from matured 1-year-old shoots. With Prunus or hawthorn these shoots are easily recognised because they are long and grow straight up. I always ask at nurseries if I can remove such shoots and make sure that I only select those that are free of virus and pests and that they have no other damage. The cut shoots should have a between 3 to 5 buds. Directly after taking the shoots they should be wrapped in a plastic bag and stored in the fridge, cooling them to between 0.5 and 3 degrees Celsius. The shoots for the scion will remain fresh for about 14 days, after which they can no longer be used for

The graft is held tightly to the rootstock while elasticised tape is wrapped around the point where both ends meet. The end should cross over your finger; then you slip the end under your finger-tip and pull your finger away. After which the tape will fit tightly around the graft.

grafting.

When to graft?

For successful grafting, it is necessary that the plant’s cells are active round the spot where you are going to graft. To promote cell activity you need a temperature of at least 13 degC, but it shouldn’t be too hot either — the maximum temperature to encourage cell activity is 32 degC. The best growing temperature is 20 degC. I start to graft hawthorn in early spring — say around the end of February or the beginning of March. The advantage of this timing is that the plant is still dormant.

Aftercare

After grafting you can place the plants in a cold frame or polytunnel in a growing bed of Torf (sifted pine bark). With plastic, protect them from severe frosts or the occasional sunny day, but remove it when it is not needed to let the plants air and prevent them from budding. Check regularly for fungi or pest attacks. In April when temperatures rise, you can plant the stock in open ground 20 centimetres apart, so that all buds receive enough sun to promote equal budding on each trunk.

After one growing season all side branches should be pruned back to 5 cm to promote a dense branch structure. The grafts can be lifted during the second year and the root ball pruned to promote a fine root structure. Even the branches are reduced at this time. To obtain a trunk with a better taper, the top is reduced to a side branch from which the trunk will grow on. If you prefer, you can choose to grow the graft in a training pot, but from my experience I can tell you that nothing beats the results you get from the open field. The trunk will thicken less in a pot.

Pests and diseases

All hawthorn are vulnerable to mildew, gall, midge and scale insects. Start to spray with pesticides before the buds sprout, to prevent growth slowing down. 

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