- Author: Edith Warkentine
If you have not already done so, it is time to prune your young fruit trees!
On February 25, 2019, Dustin Blakey demonstrated how to prune young fruit trees to a group of about 25 Master Gardeners and other home gardeners at the home orchard of Kristin Ostly. This discussion covers some of the high points of his demonstration.
The primary purpose of pruning young trees is to develop structure so that the trees will be productive in the long haul. There are two primary shapes that can be chosen: the “vase,” or the “Christmas tree.” The vase shaped, or open structure, is the most commonly used in the home orchard. This method keeps the center of the tree free of large branches to allow sunlight to reach the lower fruiting wood. The Christmas tree shape, also known as the central leader system, is frequently used in commercial orchards, to allow trees to be closer together. This method keeps trees with lateral branches arranged in separate layers and branches in lower tiers wider than those in upper ones.
As Dustin proceeded to demonstrate young fruit tree pruning he moved from tree to tree and consistently: (1) removed branches that grew to the inside of his desired vase shape; (2) where branches were competing for space, chose the more vigorous branch to survive and cut back the competing branch; (3) removed dead wood and suckers; and (4) removed branches to keep the open center, removing branches that would overly shade lower fruiting wood.
For further information see Training and Pruning Deciduous Trees, Publication 8057, UC ANR.
- Author: Ed Perry
We recently wrote the blog post “Wait! Don't Prune Apricot and Cherry Trees Just Yet,” to caution gardeners against pruning these trees in winter. Now we'd like to discuss when and how to prune avocado and citrus trees.
Avocados
Most avocado trees need little or no pruning. Whenever possible, allow them to develop naturally. Avocado leaves produce and store food for the tree. If this food supply is reduced by pruning, fruit production will also be reduced. Usually, removing dead or weak branches is the only pruning you need to do. Avoid pruning in late summer and early fall, as this stimulates new shoot growth that is susceptible to frost injury. In general, remove as few green branches and leaves as possible.
If you need to remove lower branches, prune them out completely, or cut them back to an upright growing shoot. Prune only after your tree has developed enough upper foliage to prevent sunburn damage on the lower limbs or trunk.
Sometimes a young tree grows tall without branching, grows sideways, or grows a top that is unbalanced. Correct these conditions by cutting the unruly limb or trunk back to a strong lower branch, or by staking the tree. Keep in mind that avocado trees grow naturally in an irregular way and will develop a better structure if they are not pruned at all. If you want to control the height, it's best to do so while the tree is young.
To prevent tall, upright growth, pinch back the terminal bud of the upright shoots on the young tree. Repeat this after each growth flush during the first few years. Your tree will spread out to the sides and develop a more compact form. If you reduce the size of an older tree by heading back large branches in the top of the tree, be sure to thin out the new growth which follows. Otherwise, the tree will soon grow back to its original height.
Citrus
If necessary, light pruning can be done in citrus trees any time of year. However, the best time to prune citrus is in early spring, after danger of frost has passed and before the start of spring growth.
Nearly the same rules for avocado trees apply to pruning citrus trees. The foliage of a citrus tree is an important food (carbohydrate) storage area. Pruning removes foliage and stored foods and causes the tree to produce a flush of vegetative growth instead of fruit. For the most part, prune out only dead or broken limbs.
Citrus trees normally produce vigorous shoots from the base of the tree called suckers, which you should remove as they grow. Vigorous shoots that grow from branches are called watersprouts. Remove watersprouts if they are not well placed but leave them whenever possible. Young trees need no pruning for the first two or three years after planting, except to remove suckers. As the tree grows older, prune lightly only to remove branches which are too closely spaced or entangled. Do not remove low-hanging branches, as they bear fruit within easy reach and shade the trunk and soil. The ideal citrus tree has a skirt of foliage that extends almost to the ground. Left alone, citrus trees normally develop an even, round-headed shape as they mature.
Lemons usually need a bit more pruning than other types of citrus. Cut back some of the more vigorous shoots on young trees. Lightly thin the branches of mature lemon trees each year to improve the size and quality of the fruit.
Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County.
- Author: Alison Collin
If you have fruit trees you are probably now getting a little tired of raking up fallen fruits which are the result of a natural occurrence known as the “June Drop”. This year the phenomenon is extending well into July, to the point that one wonders if there will be a crop left to harvest. So what is normal, and when do our trees need help?
Apples and pears produce several flowers on each cluster in spring, and depending on pollinator activity, and the local availability of another apple to cross pollinate, many, many flowers may set fruit. However, there will also be numerous little fruitlets that did not get pollinated properly, are damaged by insects, or require more carbohydrates than the tree can produce, and these fruits wither and fall off, frequently in large numbers.
As the remaining fruits begin to swell many more get attacked by codling moth, are affected by lack of sufficient water, or otherwise get damaged, and since the tree can only support a certain sized crop it goes through another round of shedding, usually beginning in June and continuing until early July, often resulting in carpets of larger fruit on the ground - frustratingly too immature to use for any practical purpose.
It is thought that warm nights may cause the fruit drop to be excessive since the respiration rate of the tree causes more carbohydrates to be consumed during the hours of darkness, leaving less available for fruit production.
Another factor could be lack of nitrogen, so a careful fertilization regime should be followed, being aware that too much nitrogen can also cause fruit drop and excessive growth. For information on fertilization see: http://homeorchard.ucanr.edu/The_Big_Picture/Fertilization/
In areas such as ours lack of water will also be a factor, so make sure that you check your irrigation system and remember to seasonally adjust the amount. A mature semi-dwarf tree can produce over 400 pounds of apples which, after all, are made up mainly of water!
On a large, heavy cropping tree, thinning young fruits early in the season reduces the natural shedding, and picking off any obviously damaged fruit as the season progresses will also help, but not eliminate the problem entirely. If a fruit is scarred or misshapen this will only grow with the fruit, so one might as well remove it and save the tree from wasting resources trying to get it to maturity. Infected fruits should be properly disposed of so that they do not create a source of infection. For information on thinning: http://homeorchard.ucanr.edu/The_Big_Picture/Fruit_Thinning/
Generally speaking, if the tree looks healthy and has a heavy crop of fruit falling in mid-summer should not be cause for concern.
by UC Master Gardener Cayce Hill
One of the best things about gardening in Santa Clara County is that, no matter how big your garden or how long you've been doing it, you get the sense that we're all in it together. A heat wave can wilt a single patio garden tomato as easily a 100-foot row of lettuce. Aphids don't care if you've been gardening for 30 years or just planted kale for the first time with your fingers crossed. They will find you! And so it goes with fruit trees when spring rolls around. Whether you have acres of orchards or a lone apricot in the backyard, it's time to start thinking about thinning your fruit.
If you aren't yet familiar with the concept of thinning fruit, here's a quick primer. Fruit thinning means removing excess fruit when they are between ½ inch and 1 inch in diameter. It is easiest to do this by hand, gently twisting the fruit or cutting it off with pruners. All stone fruit (peaches, apricots, nectarines, plums, etc.) requires thinning. Apples and Asian and European pears do as well. There is usually no need to thin citrus, cherries, figs, persimmons, pomegranates or nuts. Stone fruit should be thinned to 2 to 4 inches apart on each branch. Peaches and nectarines should be thinned to 3 to 5 inches. When it comes to apples and pears, which produce fruit in clusters, you should thin fruit to no more than one or two of the largest fruit per cluster. You'll be up close and personal with your fruit when you do this, so take the opportunity to remove any damaged or disfigured fruit as well.
You'll be inclined to approach this task with a light hand, perhaps even feeling bad for that little fruit. After all, baby peaches are pretty cute. But leaving too much fruit on the tree will only create problems later. All those tiny peaches grow up to be big peaches, which can add a lot of weight to your carefully-pruned (it is, isn't it?) tree. Fruit trees typically set much more fruit than they can support which can be a drain on the tree's stored energy and even cause it to bear fruit every other year (alternate bearing cycle.) By thinning the fruit, you help to prevent these problems and maximize the size of the fruit you leave on the tree!
If this sounds like a lot of work, don't worry. Mother Nature is here to help. During “June drop” (which often happens in May around here) fruit and nut trees naturally thin themselves a bit. So there's nothing wrong with your apple tree if it sheds crop of immature fruit. And all your efforts will be rewarded when you finally take a bite of that ripe, juicy peach!
For more information:
Home Orchard: Growing Your Own Deciduous Fruit and Nut Trees by C. Ingels, P.Geisel, M. Norton
This article first appeared in the April 2, 2016 issue of the Morgan Hill Times.
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- Author: Alison Collin
Optimum growing and pollinating conditions lead fruit trees such as apples, peaches and plums to set far more fruit than the tree can sustain to maturity. If all these fruits are left on the tree they will be small and of poor quality and the total weight of such a load on the branches will cause them to break off or split at the crotch, often causing severe damage to the tree. Crowded fruits also encourage pests such as codling moths and diseases such as brown rot and scab. Over-cropping prevents the tree from putting energy into producing flower buds for the following year which will be detrimental to that crop. Apple varieties with biennial patterns of production - those with cycles that produce a bumper crop one year and nothing the next - may be induced to fruit annually by drastically thinning early during the productive year, even to the point of removing all flowers from alternate spurs.
Many trees shed part of their crop naturally, a process known as “the June Drop” but which can begin during May in California. However, this is often not sufficient to produce quality fruit at harvest.
One of the most psychologically challenging tasks that a gardener faces is removing perfectly healthy fruit (sometimes by the bucketful) in order to leave more manageable numbers. The earlier in the season that the surplus fruits are removed, the larger the individual remaining fruits will become. It takes some seasons of experience to judge how many fruits to remove but a steely resolve will be amply rewarded. The largest fruit in any cluster is usually left, unless it is obviously damaged.
Apples: These should be thinned to one or two fruits per cluster depending on variety and the overall set of flowers. One fruit per spur 6-8 inches apart is the aim but, if the overall crop is light, clusters of two may be left. Realistically the fruit often grows in frustrating patterns with groups of 5 beautiful apples on one spur and then several spurs with no really good fruits forcing a decision as to whether or not to leave two fruits on the good spur! Fruitlets are removed using scissors or other fine cutters which can reach inside the cluster to the stem. These can be cut close to the fruit and the little stem may be left without any detrimental effect. It is vital not to just pull on the fruit since this will often drag the whole spur off the branch. Some gardeners grasp the stem of the fruit between their first two fingers and “roll” the fruit off with their thumb. There are usually a variety of sizes and shapes in each cluster so begin by removing the small, damaged and misshapen ones first. Then there is the agonizing decision of which of the remaining two perfect fruit to leave. I find that usually one has a slightly thicker stem than its partner so I would leave that. In order to get the best sized fruit at harvest the ideal leaf to fruit ratio for apples would be around 75:1 for early varieties down to 40:1 for the later ones, but who's counting!
Peaches: The same basic principles apply but a little more space is usually left between fruit – about 6- 9 inches. However they grow much tighter to the stem and are best removed by grasping the fruit firmly and twisting it round until it detaches. For those just out of reach, I have found that barbecue tongs (the sort with a looped end) make an efficient removal tool.
Plums: Thin to about 3-4 inches apart. Overloaded plums will naturally drop fruit at the stone hardening stage, so sometimes growers thin in two stages; lightly when the fruits are small, and then finally once the natural dropping has ceased.
Cherries and Nuts are not usually thinned.
Pears: Often thin themselves, but if extra thinning is needed in order to end up with one pear per spur, the time to do this is when the fruitlets begin to turn downwards.
Thinning is undoubtedly a rather tedious business, but when harvest time comes and the fruits are large, lush and healthy, you will be so pleased that you made the effort.