Step-by-step guide to Swiss pruning. Reshaping fruit trees into pyramids can boost their productivity
In the decade preceding World War II, a professor at the Oeschberg-Koppigen Horticultural School in Bern, the Swiss capital, took a hard look at conventional fruit-tree pruning methods and decided that there was a better way to go. Specifically, Hans Spreng believed that he could reduce a tree's overall size and boost its productivity at one and the same time by reshaping the tree.
Conventional pruning methods, still widely practiced around the world today, produce a tree that is relatively small at the base, broadening out into a wide dome shape at the top. Professor Spreng, on the other hand, felt the trees should be pyramid- or cone-shaped, wide at the base and growing to a point at the top. This would allow for good penetration of light throughout the tree, resulting in optimum photosynthesis. Moreover, it would put the bulk of the tree's fruit in the broad area near the b ottom where it could be most easily reached.
Trials proved the theory correct, and soon the radical new approach became standard practice in the canton of Bern. From there it spread to the rest of Switzerland and after war clouds cleared from the skies of Europe, it crossed into neighboring countries.
One of Mr. Spreng's students in those early years was French-speaking Jean Richard, who emigrated to Canada, settling first in Quebec in 1961. On various fruit farms Mr. Richard quickly found that what the Swiss call the Oeschberg method of pruning, which Canadians term the Swiss method, worked every bit as well on this side of the Atlantic as it did in Europe.
Because it is a radical departure from long-established pruning practices, the new method was at first greeted with skepticism in Canada, just as it was in Switzerland. But Richard made the point simply by practicing the method and letting the results speak for themselves. They spoke loudly, so much so that soon he was approached to teach courses in the Swiss method. Recently he lectured on the topic at the National Organic Farmers Association convention in Rutland, Vt. His method is also detailed in the book ``Ecological Fruit Production in the North,'' which he co-wrote and published with Bart Hall-Beyer of Scotstown, Quebec.
Originally practiced on apple and pear trees, the method has been found to be equally effective with all the stone fruits -- peaches, plums, nectarines, and the like.
The Swiss method of pruning promises to rejuvenate old apple trees, adding, in Richard's experience, ``10 to 20 years'' of additional heavy fruit production. It does this by reshaping the tree, removing vigorous vertical branches, and channeling the tree's energy into lower, downward-pointing branches. While these lower branches may appear rather spindly at first, they have tremendous potential for fruit-spur development, which is the key to the success of the Swiss system. This is how to rejuvenate an
old apple tree by Mr. Richard's method:
First year. Study the tree and try to visualize which of the vertical branches should be removed to achieve the desired conical shape. This evaluation is important, Richard points out, since as much as a third of the tree may be removed the first year. Identify the weaker downward-growing branches that will remain to become the heavy fruiting members of the tree. Remove all branches, even vigorous fruiting ones, that do not contribute to the desired conical shape.
Of the remaining branches, prune off the upward-pointing small stems to encourage the downward-pointing stems (see illustrations). Remember, Richard cautions, rejuvenation is a once-in-a-lifetime thing for the tree; thereafter only maintenance pruning is required to retain the fruit-intensive shape.
Second and third years. Remove all upward-pointing branches. After the first heavy pruning there is often a vigorous response from the tree, which sends many new branches reaching for the sky. ``Be ruthless'' with these, Richard cautions, and remove all of them; otherwise, they will quickly sap energy from the lower branches you wish to encourage. Occasionally an upward-pointing branch can be bent or weighted down into the desired growth pattern, but this need only be done if you see an empty low space
that needs filling in.
Subsequent years. After the second year the tree's response to pruning appears to change slightly. The lion's share of new growth no longer goes to the upward-growing branches, but tends to be shared more equally among all branches. In this year there is often a marked increase in growth of the lower branches. From now on maintenance pruning is all that's necessary.
Richard points out that the principal reason for the success of this method of pruning is that fruiting buds, though often dormant, are much more closely spaced on the lower branches, compared with the vigorous branches high up in the tree. So by diverting energy into lower parts of the tree you rouse many of these buds from dormancy and effectively boost fruit production while reducing overall tree growth.
Mr. Richard's experience has shown that the heavy pruning involved should be practiced in the spring (February through April) in the colder parts of North America to avert injury to the tree. In warmer regions, rigid adherence to the spring schedule is not so important.
``Ecological Fruit Production in the North'' ($11 US, $13.50 Canadian) is available from Progressive Agri-Systems Inc., 201 Center Street, Stockertown, Pa. 18083, or from Bart Hall-Beyer, Sursum Corda, RR3, Scotstown, Quebec J0B 3B0.