I have some thoughts on when is the right time of year to prune pomiferous (pomes like apples, etc.) and drupiferous (drupes as in stone fruits) fruit trees.
To me, there seem to be more negatives for pruning when the trees are dormant in the dead of Winter than there are positives for doing so. I am beginning to think that the primary reason Winter (dormant) pruning became the norm was for the convenience of the pruner. It is so much easier to see what you are doing and to gain access to a leafless tree than a leafed tree. Plus, in Winter, you donât have to worry about damaging flowers or developing fruit. However, unless you prune just as the tree is ready to start sprouting, the cuts do not begin to heal until the cambium layer becomes active as temperatures warm in Spring. Seems it would leave the cuts open to disease longer if not quickly healed by cambial activity. Secondly, wet Winter weather is more likely to wash disease (spores) into the unhealed wound during this time. This is why it is recommended that pruning be done at the beginning of a dry spell. Also, trees (especially stone fruits) are much more likely to develop âwaterâ sprouts if pruned in the dormant season (There is a botanical reason for this not covered here.)
These are all negatives that do not exist if pome and stone fruit trees are pruned in late Summer. To me, most pome and stone fruit tree pruning is best done in late Summer even though there is a loss of fruit and it is more difficult to see what you are doing. There is faster healing, the introduction of disease is reduced in dry weather, and the apical dominance of buds near the tip of cuts has time to reestablish before growth resumption the following year thereby reducing the occurrence of âwaterâ sprouts.
I agree completely Paul. I think many large operations prune when it is most economical for them from a labor perspective. For the home enthusiast, without those constraints, I think pruning while the tree is actively growing and the weather is dry is a better option for all of the reasons you point out.
You canât prune for scions in the summer though⌠If you are trying to prune and get wood to save, winter is the only option.
Additionally, there are fewer bugs awake to munch on exposed wood in the winter and you run less of a risk of getting fireblight based on my understanding (assuming you are in a cold area). Iâm just learning though, so please correct me if I am wrong.
Youâre quite right about harvesting scion wood, but that can be a separate operation from pruning. Light pruning can be done any time of year. Especially if you need to remove any 3D (diseased, damaged, or dead) wood.
I donât think bugs are a big issue compared to the entrance of bacteria and fungal spores though damage caused by bugs does leave an opening for infection. Fireblight is caused by a bacterium that is spread readily during rainy weather.
Bug damage or pruning damage opens a tree to possible infection by several bacterial or fungal diseases so minimize the infection risk by pruning during a dry spell. Also, disinfecting your tools between trees will reduce passing a disease.from tree to tree. If you cut off diseased material, burn it or bag it and put the diseased material in the trash, and be sure to remember to disinfect your tools.
You are in Z8, in colder climates the rules are different because time of pruning not only affects winter hardening off but also can lead to injuring and even killing trees when extreme cold follows.
The general consensus of the literature is that dormant pruning is less dwarfing than pruning after growth begins, which makes sense. However, in cold climates it is often recommended to prune in early spring and not in the winter at all. For peaches, quick healing of wounds can be important to ward off canker in some orchards so commercial guidelines tend to recommend pruning after growth begins. Sometimes such literature recommends pruning cherries during dry spells in the summer, also because of concerns about canker.
I donât believe these matters have been researched to the point of clarity and are much influenced by âlogical deductionâ. Often commercial growers develop their own schedules that defy the literature, which I learned decades ago when a commercial apple grower told me that he used the same crew to prune the apple trees as the one that just finished harvesting them, meaning he pruned the trees when still in leaf in the fall. Heâd been doing this for several decades and knew other growers who did the same, so this did a great deal in calming my fears about when to prune bearing age apple trees here in Z6.
The same grower pruned his peaches before they started growth but was careful to do so after the coldest days of winter- usually in early spring. I believe Iâve killed a couple of young peach trees by pruning an orchard immediately before an unpredicted drop in temps into single digits in mid Feb. Older peach trees in the orchard were fine but all of the young trees seemed to suffer varying degrees of cold injury as a result of the pruning wounds. Iâve read that late summer pruning of peaches can also damage their ability to harden off.
Another important point about peaches and nectarines is that if you wait until bloom to prune you have a much better idea how the flower buds survived winter and make sure you arenât removing a lot of the potential crop. Sometimes flower buds on weak wood are more hardy than those on strong.
At any rate, once trees reach the desired size, there is no harm in pruning them after they start growth and for beginners I recommend it just so they can see where the flowers are. Especially for apples and pears this can be instructive on what you want to remove. Often the best flowers are on more vigorous shoots if they have flowers at all. Many apple varieties produce their best crop on such shoots in their second year- a point rarely observed in the literature.
Very good point.
I like your common sense approach. I get lost in all of the âscience talkâ . . . forever the layman (or woman) - no matter what the topic, it seems.
Techniques have to be adjusted to the local conditions. But, pruning in the dead of Winter when the plant is fully dormant and cannot immediately start healing is probably not a plan. As Alan mentioned, pruning in late Winter or early Spring when the tree is getting ready to bud and the cabium layer has become active allows for healing to start right away. But, since pruning during the period of cambial activity usually stimulates growth, the plant may be made vulnerable to freeze damage or death.
As for late Summer to early Fall pruning, it depends on the type of plant. Roses pruned this time of year are usually stimulated to produce new growth which is readily killed by freezing temperatures. Plants that die from a cold snap do not do so simply because of pruning. The real problem for SOME TYPES of plants is that the pruning stimulates cambial activity. The active cambium layer has newly formed cells which are readily killed by freezing. If the cambial layer cells die, the tree dies. So, pruning some kinds of plants in late Summer or early Fall can be fatal or highly damaging to the plant. The very same reason for damage or death can occur if a plant starts to bud in the Spring and is then exposed to a hard frost or freeze. Iâve had some of my apple trees killed by late freezes after they had begun to bud. The cambium layer during full dormancy (temperate zones) is inactive and there are no newly formed cells that may be highly susceptible to freeze damage. The cambium is active roughly from Spring through Fall with the greatest amount of activity from Spring through early Summer. In late Summer, cambial activity slows,(but doesnât stop until full dormancy) as the plant prepares to enter dormancy. Several kinds of cells are formed by the cambium with a difference in their proportions during growth in Spring and Summer. This is what forms the Spring wood and Summer wood of the growth rings seen in temperate zone trees. As to be expected, different plant populations vary significantly in their tolerance to different environmental parameters such as temperature, humidity, moisture availability, pH, etc., so some are damaged by a light freeze while others tolerate a hard freeze. Late Summer/early Fall is when the cambium is closing down for Winter and in many plants, judicious pruning will not reactivate it. Neither will full dormancy Winter pruning reactivate the cambium.
As for cambium activity, the generally considered best time to prune most - definitely not all - ornamental flowering plants is right after they bloom just as their cambial layer is cranking up for a period of rapid growth - also and healing. Knowing the activity level of the cambium is important to pruning. People doing plant grafting pay close attention to cambial activity.
Bottom line is knowing the characteristics of the specific types of plants you are pruning is important.
Absolutely, I often use so-called âwaterâ sprouts to manage the shape of my apple trees. As pointed out by Alan, they usually become highly productive fruiting shoots is a couple years. Not all that easy to get them to grow where you want them though. Good scion wood, too.
We all start off as laymen, but common sense based on a degree of knowledge goes a long ways. Slowly, slowly, catch the knowledge. Couldnât resist that one.
When Iâm pruning, and especially with upright growing varieties of apple trees, I often spend a good deal of time and electric tape and string pulling down upright shoots, or, more often, 2-year wood into a more horizontal position- I also will simply pull them under existing branches. On scaffolds I am regularly cycling out old secondary branches whose diameter is too large to keep in check (from being excessively vegetative) and replacing with new branches. On central leaders, everything above the first tier tends to be cycled in and eventually replaced to keep the upper from dominating the lower tiers.
When Iâm training a new graft to replace an existing scaffold, I use that existing one to anchor the water sprout I graft the new wood onto, usually beginning on the second year to gradually pull the vigorous graft growth to a more horizontal position. The longer you can keep it upright the more vigorously it will grow so often end up having to use hinges to bend a grafted watersprout-become branch without breaking it.
No, Iâve been pruning every day since about Dec. 15th and I wonât have all the orchards I manage pruned until April. You can prune established apple trees any time in my zone, they wonât experience injury as long as temps donât quickly drop well below -20F, at least for most varieties.
I need to prune constantly for over 6 months of the year to keep up and my business is based on doing this. Iâve even begun pruning mature pears just as early because we donât seem to get to extreme cold anymore, itâs become rare to even get below 0F.
As mentioned in my original post, the problem with Winter pruning is not the cold. After all, a dormant cambium is not as readily damaged by cold as an active cambium is. I, too, do some dead of Winter pruning, BUT I wait until a dry spell is forecast.
The pronounced problem of Winter pruning is entrance of diseases in cuts washed there by rain. I live in an area of ample, heavy Winter rain. For example, fireblight is a problem transferred by rain.
Secondly, Winter pruning, especially heavy Winter pruning, stimulates the growth of an excessive number of âwaterâ sprouts. And yes, some of these sprouts are located well and can be turned into useful fruiting limbs, BUT, usually, a very large number of the âwaterâ sprouts have to be cut off thereby creating even more injured surface through which disease can enter. And, it also means more pruning to be done
All dormant pruning creates water sprouts- equally so- we are attempting to create a more open tree to get light well distributed throughout the tree while trees on vigorous enough rootstocks to be free standing try to close out the canopy in order to assure their dominance of it, whence, water sprouts. I have trees that I maintain only with mid-summer pruning and they too will have water sprouts again by mid-summer the next season. Summer pruned trees generally do grow with somewhat less vigor overall including their water sprouts
I prune apple trees in rain, or snow if it isnât too unpleasant to be outside and I donât associate pruning wounds with FB because that generally enters either through flowers or shoot tips in spring, or even summer in the case of shoot blight. Most of the fireblight I see is shoot blight during summer on apple trees.
If you have something in the literature that backs your theories or anecdotal experiences of the harm that has occured when you have pruned at a certain time please share it. For the last 3 decades your concerns have not been issues with the orchards I manage and I will stick with the adage that the right time to prune is when the pruners are sharp- at least for mature apple trees.
My point exactly. Not too much with Summer pruning. The literature actually does indicate that fireblight is transmitted by insect visitation - to flowers, to buds, to young stems, and to wounds, but it indicates that it is ALSO transmitted by the washing action of rain carrying the bacterium into wounds⌠This form of transmission is not limited to fireblight.
What Iâm saying is that the problems you are mentioning are not significant enough to alter pruning times for in my region. In 30 years managing hundreds of trees every season the only species Iâve ever had killed by fireblight has been a couple of pear trees. Diseases of the trunks are not prevalent at all.
There may be diseases pressure in some parts of the country where this isnât true, but I donât like the idea of just stating opinions about time of pruning that are only logical leaps and not also based on how commercial producers are managing trees there or research based information that is evaluating risk.
I do look for dry periods when summer pruning pears, but Iâm unaware of any research that suggests that dormant pruning them renders them more susceptible, and FB is well studied-it is only transmitted during a very narrow window of weather conditions. Maybe you have something?
No, I believe vigorous apple trees, when summer pruned send out an equal amount of water sprouts from summer pruned trees the following season- they may not get as large, but what difference does is make? One possible difference is that the water sprouts will block sun from the spur leaves the following spring more than they would if winter pruned because new growth will have started during the remaining summer and early fall instead of having to start growth anew in spring. On my favorite trees that are susceptible to biennial bearing I remove unneeded water sprouts and even unneeded less vigorous shoots while Iâm hand thinning so spur leaves receive as much sun as possible. It is the 3 weeks post petal fall that are most important in a trees âdecisionâ to invest in flower buds for then next year.
I donât know if summer pruning only is better or worse for apple production, but to me worst seems most likely, considering Iâve never heard of commercial orchards only pruning in the summer or read any university guidelines for commercial production even suggesting it as a possibility. When I do it a customer is already getting more apples than they can use and are trying to reduce maintenance costs. Sometimes it reduces vigor excessively and I have to return to dormant pruning.
Iâm also a beekeeper, and beekeepers know that if you ask 100 beekeepers the same question, youâll get 100 different answers. The ideas written are not originally mine, but are a amalgamation of the writings of a number of professional horticulturalists. I think it is fairly clear that Summer pruning is more directed at the backyard orchardist and not at large-scale, commercial operations. It would seem that Summer pruning would be highly impractical in commercial orchards for a number of reasons.
I donât think âwaterâ sprouts are bad, and I sometimes encourage them. But, a large number of open cuts does increase disease, and pruning during dry weather becomes more important. Where I see âwaterâ sprouts encouraged in my area is by home orchardists that do Swiss-style pruning. I see a lot because the Swiss were a major group of settlers here. Theyâll do a DRASTIC late Winter/early Spring pruning and after leaf drop that same rear, the trees look like pincushions. Two years later, they thin and head back. The cycle is repeated after several years to renew the fruiting wood. Believers say it is absolutely the best method, and you will not change their minds. It works, and certainly a lot of fruit is produced because of the branch angles, but I would guess it would not in any way be viable as a method for a large-scale, commercial orchard. However, there are always exceptions so there probably are Swiss-style pruned large-scale, commercial orchards somewhere out there.
My comments were meant to give home orchardists some thoughts to consider.
Laissez le bon temps rouler!
Did you mean to say a "not in any way ⌠"?
Thank you Mark nmt,
ânotâ should be there.
My comments were to assure members know how experienced growers manage their trees and how the literature suggests it be done as I understand it. Pruning is complicated and difficult enough when only dealing with research and experience based information.
There are a ample amounts of both research and experience behind advocating Summer pruning.
To reiterate and repost another post:
The effects of pruning and the level of cambium activity are directly correlated.
The science behind it is that the cambium layer is at its highest level of activity from early Spring to mid Summer (climate dependent). Buds become active and growth is vigorous during this period. Apical dominance directs most growth, but not all growth, to the shoot tip. Cut off the shoot tip during this period will induce buds further down the shoot to start growing - many of them and water sprouts will form readily. But, an active cambium means the cuts will heal quickly. Also, the âSpring woodâ of this yearâs growth ring forms by cambium activity during this period.
Cambial activity slows greatly in mid Summer to early Fall (climate dependent). In mid Summer, the level of cambium activity decreases, but the cambium does not become inactive. Growth of shoots slows and almost stops, and this yearâs buds start to harden for dormancy. The âSummer woodâ of this yearâs growth ring forms by cambium activity during this period. To me, this is the best time to prune: dry weather, rapid healing, less rampant growth such as water sprouts (cut off water sprouts also means more cuts that are exposed to disease), etc.
So, pruning in Winter is, in at least one way, like pruning in Spring with regard to the eager growth of water sprouts as the tree is just waiting a bit longer to start growth with the warmer weather of Spring and renewed vigorous cambium activity.
A WINTER PRUNING HAIKU
NO CAMBIUM ACTIVITY
NO HEALING
NO GOOD!
The contributions a of apical meristems and marginal meristems were ommitted to reduce the length of the post.