Stone Fruit Notes – Bench Grafting
Does Summer Pruning Benefit Apple and Peach Trees?
Stone Fruit Notes – Bench Grafting
by Bob Purvis
From the Grapevine Winter (December) 2009
I’ve been bench-grafting stone fruit now for over 15 years and still do not consider that I know everything there is to know about it. Regarding cherries, the consensus among the nurserymen I know is that spring grafting of cherries works best when the trees are dormant and it is cold. For cherry bench grafts, it seems that temperatures of 40-45°F for storage are best, so that the buds do not begin to move before a union is formed.
For plums, Cummins Nursery in NY told me that they keep plum bench grafts at 40-45°F, but I have had good success with holding plum bench grafts at temperatures of 55-65°F, so as with so many other things, plums seem to be adaptable.
For apricots, Garfield next door has field-grafted them when the rootstock buds are just beginning to swell and had a good take rate. (But, we are in a Zone 7 climate here, and it warms up quickly in April.) For bench grafts, temperatures around 65-70°F are adequate to promote callusing for Canadian and other cold-hardy apricots (Jerseycot and Alfred), but any apricot that requires a fair amount of sustained heat before it breaks dormancy–Brookcot, Montrose, Afghanistan, Suphany, and Zard–really needs to be kept at warmer temperatures (70-80°F). I was using a hot-callusing tube at those temperatures, laying the graft unions on the slots thereon and covering the rootstocks’ roots with sawdust. Unfortunately, when you find a graft has taken and you remove it from the sawdust, a lot of new hair roots get broken; and when you plant the graft out in the field, the rootstock has to form roots all over again. This can result in transplant shock for the scion. In spite of this, I had a 75% “take” rate on my apricot grafts in 2008. But, I lost 64 of 65 after planting them in the field late (early June), with complications of high levels of sodium and boron and imperfect irrigation. Poor care of rootstocks this spring resulted in a success rate of only about 25% on my apricot and plum bench grafts.
Justin Martin, a Nebraska horticulturist and member of the Apricot Interest Group, shared with me what I consider a better method than mine. He chip-buds the rootstocks, bundles them so the chips are not broken off, and then puts the roots in plastic bags with no mulch around them, wetting them down and keeping the new chip-buds inside the bag. He lets the tops of the rootstocks sit in the open air and keeps the bags at 70-75°F (on top of his refrigerator). Every other day, he opens the bags and sprays the roots with water so they stay moist. Justin said that after 10-14 days, 132 of 139 chip buds had turned green. At that point (early April), he planted the budded rootstocks in the field and cut them off just above the bud. Inside the bag, the rootstocks formed root initials, but since the roots were in air, they did not develop roots.
Once the rootstocks were put in soil, roots began to develop rapidly, judging from development of the tops. One minor drawback is that after 10-14 days in a moist warm environment, mold begins to develop on the roots. However, with the tops of the rootstocks beginning to break bud, there is a flow of sap past the chip and good cambial activity to promote a bud union. Furthermore, there is not the perplexing problem of what to do with suckers that often arise below a graft union, nor the breakage of root hairs after removal from sawdust or sand. So, I intend to try this technique next spring with at least some of my apricot grafts and perhaps compare it with my current method.
Concerning spring propagation of peaches, I believe Justin’s technique would work well as long as the chip buds are kept very warm (ideally, 75-85°F). I have never had success bench-grafting peaches in the spring, but Bob Kurle and other people have been able to. The worst thing I find about dormant peach scions is that they have a punky interior, and it is very difficult to make whip and tongue cuts on them, and therefore difficult to make a good graft.
Wishing you all a Merry Christmas and a Happy New Year,
Sincerely, Bob Purvis
Does Summer Pruning Benefit Apple and Peach Trees?
By Mosbah Kushad (kushad@illinois.edu)
Reprinted with permission from the Illinois Fruit and Vegetable News, University of Illinois, Urbana‐Champaign, Vol. 19, No. 6, June 6, 2013
Reprinted from the Grapevine, Summer (June) 2013
For more than a century, pomologists have been evaluating summer pruning, but there is no consistent agreement about its benefits. Some experiments have reported that summer pruning reduced tree vigor, increased flower bud initiation, and improved fruit color, while others showed it had minimal or opposite effects. Some of the discrepancies in results relate to when and how summer pruning was done. Several reviews were published on the subject in the mid 1980s, but very little have been published since then. Here are a few suggestions about summer pruning.
There is a general agreement that removal of shading branches by winter and summer pruning increases light penetration into the canopy. It is also known that an adequate amount of light reaching fruiting wood is critical for new flower bud formation. By increasing the amount of light in the canopy, early summer pruning of peaches and apples has been suggested to increase flower bud initiation in the following year and maintain fruiting wood, but the results are not consistent. Because of this, my suggestion to those that wish to summer prune their trees, especially peaches, is to remove only vigorous upright shoots (water‐sprouts) in the middle of the canopy and some of the non‐fruiting shoots that are causing shading. It is better to pull them out by hand or thin them out, because there will be very little re‐growth in the same area. Also, do not prune the trees very severely because it can reduce the reserve carbohydrates in the tree which can impact fruit size and sugars. It can also increase the trees’
susceptibility to early winter injury and formation of nonproductive lateral branches.
Timing of summer pruning is also important. Very early summer pruning will affect the vegetative growth while very late summer pruning will add little benefit to the trees or the fruits and in worst situations it may reduce winter hardiness. The preferred time for summer pruning is about 40 to 50 days after bloom for peaches and 50 to 60 days after bloom for apples. The idea is to get rid of a few vigorous upright shoots in order to increase light penetration into the canopy, but this is not a replacement for dormant pruning.
In general, a well pruned and trained apple or peach tree with good light distribution in the canopy will not gain much benefit from summer pruning, so spending too much time on it is not economical.
http://ipm.illinois.edu/ifvn/contents.php
https://ipm.illinois.edu/ifvn/pdf/frveg1906.pdf