Winter Fertilizing Fruit Trees


#1

I have been reading a variety of articles and research papers regarding winter fertilizing trees. By winter, Im referring to the range from early to late winter. Most of the articles that I read from scientific literature refer to recent plantings, such as for nurseries or evergreen groves. The results do not appear clear cut. They also do not extrapolate well to a home orchard. In some cases, there was increased growth - height and trunk girth - the next season, or the leaves were greener.

I wonder if anyone fertilizes their fruit trees and plants during the winter? I have not done a controlled experiment. I could see it being helpful. Spring is a busy time, and it’s hard to get everything done. Especially for someone slow, like me, or someone busy. Fertilizing now would be one less thing for later. Some writers think that as long as the ground is not frozen, tree roots take up and store some nutrients, for better growth during the most active early growing season.

Since we use a woodstove, we have a lot of wood ash, rich in calcium (roughly half that of lime) much needed in my acidic, low calcium soil, potassium, and some other minerals. The winter and early Spring rains seem to wash the ashes into the soil. For nitrogen, a urea fertilizer might soak into the soil into the root zone, better during the wet season than later.

On the negative side, nobody wants to pollute the groundwater or waterways with nitrogen and phosphorus fertilizers that wind up leaching without being taken up into tree roots and grasses or other plants. Possibly with fertilizing, would Spring growth be more lush and more susceptible to late frosts?

I was wondering what others think, and especially the voice of experience on growingfruit.org. During most winters, at least my fig trees get a dusting of wood ashes, and I don’t see any harmful after effects. Also around some young shade trees. Most of the rest of the ashes go to kitchen garden beds, especially for tomatoes, greens, and sweetcorn. But I was wondering about fruit trees, brambles, and vines. As for nitrogen, I’ve done that with chestnut trees, bamboo, and cypress, but not most of the fruit trees.

Thoughts? Experiences?


#2

I have put wood ashes around apples and pears. They certainly did no harm.


#3

Trees won’t take up much if any fertilizer when they don’t have leaves. In other words if the plants aren’t taking up water they won’t take up fertilizer. In a rainy climate I just can’t see winter fertilization being a good practice. It is going to lead to excess leaching of nutrients into the ground water.

I can fertilize my trees in a matter of minutes. Is it really that big of a task that it needs to be done now?

Even with very dry winters I wait until spring.


#4

maybe organic fertilizers like bone and blood meal would work to put down as it takes time to break down before the plant can use it. for commercial , id wait till early spring.


#5

I focus on feeding the soil biology under my trees. As long as I keep them happy, they’ll feed my trees whatever they need. In late fall I spread horse manure compost, covered with hay mulch, underneath my trees. I would recommend this for anyone who’s ground is not frozen at this point.


#6

How do they start braking bud and blooming, like my apples and pears are now? Is it just from stored energy in the roots? Just asking, because I am curious.

TFN


#7

The buds break using energy stored in the buds and wood. But I may not understand what you are asking.

Trees don’t use much water when they don’t have leaves. There is very little water loss from the bare wood in winter. Most of the nutrients are carried into the tree along with the water. So water and nutrient uptake happens when there are leaves on the tree.


#8

Thanks, fruitnut, that was what I wanted to know. Some of my trees are about to bloom if it doesn’t cool back down some, and I was wondering if I should get ready to fertilize them.

TFN


#9

Yes right as always. I take late winter pruning’s and use them like flowers. Put them in a vase and enjoy the peach or plum blooms right in my house. Without stored energy, this could not happen.I would otherwise discard as i winter prune it for structure. Using BYOC (Backyard Orchard Culture) techniques require frequent pruning. I must say doing it 6 years now, it works very well. All my trees are 7 foot tall.I get about 80 fruits off of them, sometimes less depending on thinning. I’m doing some renewal pruning next time and will cut some scaffolds down to 4 feet. I have some new grafts lower on more lateral branches and want them to take over the scaffold, besides just renewing the wood. See how it works, if it works? I believe it will, but either way I learn something.


#10

Generally, studying research that might be useful to the home grower is interesting but can be misleading. Most of the time commercial growers adapt to research and follow the most recent, adequately tested research- they have to. Bringing whips into productivity even a year sooner would make a huge difference in already thin profit margins.

That said, I have heard of commercial fruit producers using varying timing protocol, but this is sometimes linked to the species they grow- obviously citrus could easily respond to fertilizer differently than trees with a different cycle of dormancy.

For nutrients that are held by the soil and need to work their way down, such as potassium, fall fertilization if often recommended, although sandy soils may require spring fertilization because they do a poor job of holding K.

The nitrogen in urea takes the longest to disappear of quick release N, and is the most common form used in fruit production. In NY it is almost universally applied in spring just BEFORE first growth. I believe FN may be mistaken that absorption is reliant on transpirational pull. Here is something I just pulled out of a research paper on fertilizing pecans.

“The primary times of N absorption were while the
tree was dormant (November to February or November to April,
i.e., leaf fall to budbreak) and April through May (budbreak
through rapid shoot and leaf expansion),”

I believe that N absorption is reliant primarily on the growth of fine roots, which can happen using stored energy without the existence of leaves that pull sap up a tree. I think that the leaves are needed to pull the N to the branches and leaves but that it is helpful for fruit trees to get an N boost as early as possible by having it in the roots for rapid transferal to the leaf and flower buds as soon as transpiration begins. Soil temps play a strong role in fine root growth, so the whole process is variable and complex.

For getting best growth for establishing trees, nitrogen, in most soils, is the holly grail- the only nutrient to make a measurable difference in growth and speed of establishment. Needs change after establishment as other nutrients are removed from the soil via the harvest.

I find that I get excellent results by applying 90-day encapsulated urea just before or at first growth in spring. For stonefruit, another app of straight urea 90 days later may be useful but I don’t apply any after July.

Here is some interesting information about potential advantages to continuous light fertilization for the establishment of orange trees.

For those interested in potential winter injury from fall fertilization, I recommend a search with these words, FALL FERTILIZATION AND COLD HARDINESS IN
LANDSCAPE TREES
By E. Thomas Smiley1 and A.M. Shirazi2

Here is what the Haifa group has to say about nitrogen for N. Carolina peach growing for BEARING trees. They seem to assume that absorption occurs before substantial leaf growth.

Nitrogen can be applied in early winter (mid December) on heavy soils or in the early spring before bud swell. On sandy soils in North Carolina, it is best to apply nitrogen in the spring just before or during bud break. Summer nitrogen applications are not recommended. For orchards on piedmont soils that have a high native fertility, the lower rates of nitrogen in Table 4 should be adequate for good tree growth and fruit production. On sandy soils, the higher rate should be used.

A split application of nitrogen fertilizer is highly recommended in North Carolina because of the high probability of a spring frost or freeze in many locations. Half of the fertilizer is applied in late February or early March; if a crop is set, the other half is applied in late April or early May. For trees on sandy soils, a third nitrogen application may be necessary. Nitrogen should not be applied after June 15 to avoid winter injury and decreased fruit quality.
If terminal shoot growth is too vigorous (more than 12 to 18 inches), reduce the amount of nitrogen applied. If terminal growth is weak (less than 6 to 8 inches), increase the amount of nitrogen.


#11

Alan do you have a brand you like better than others for the urea? Thanks


#12

Straight urea is all the same. I buy the 90 day stuff in bulk (they don’t even bag it for me) and I forget what it’s called, but mostly it’s used to grow corn. It is cheap but hi-tec enough to release fairly consistently regardless of weather. I’m sure most agricultural suppliers sell the same brand if you ask for 90-day encapsulated urea. Some will probably provide it by the 40 pound bag.

When I check fertilizer prices at the big box stores I’m amazed at the high mark-up and the poor selection of lawn fertilizers, although they do carry one Osmocote formula that works great for container plants- 6 month 15-9-12 with micros. You have to go to more specialized ag-stores to find straight urea and N is so much cheaper when you buy it that way than in Scott’s lawn fertilizer.


#13

How much do you apply


#14

I spread about a half cup under the branch spread of 1.5" to 2" caliber trees. Not more than a cup.


#15

Thanks Alan for the detailed and interesting information. I’ve been trying to be scientific about this, and also use experience as my guide. That is why I asked on this forum. My soil was probably once Douglas Fir forest, which historically underwent several burns and ultimate clearing. It was farmed and is now somewhat poorly drained, heavy soil. My orchard was mostly either rough grass or massive blackberry bramble, which I cleared. Even the grass and weeds were rough looking and not vigorous. Soil testing showed acidic soil, low calcium, high potassium, high phosphorus, and very high iron, among other traits. We have rain during the winter, but almost no rain in the summer.

One thing I wondered about is exactly how fast does nitrogen leach? I don’t know. If it leaches, say, a foot a month into the soil, then it’s possible that winter fertilizing is feeding the soil which then feed the trees as soon as they resume growth. And those feeder roots. I need to do some more research, of course, and read what is said here.


#16

Thanks Fruitnut for this information. Fertilizing can be a task that gets left on the back burner during a season when there is a lot of other work going on. I need to pace myself. Anything I can do during the off season helps, plus it gets me into the garden and orchard, hopefully doing something useful, so I’m not cooped up inside in the winter.

However, I don’t want to waste fertilizer or effort if it’s not useful or possibly harmful to do it at this time. So again, thanks for the information.


#17

How is this ?


#18

That’s it, your cheapest form of quick release N.

90 day costs more- both do tend to acidify soil.


#19

This!
Add compost in droves in early spring, or add mostly composted manure. Top it off with tons of leaves. The soil organisms will be really happy and will eventually feed your tree throughout the entire season.


#20

But keep in mind, that more is not always better. The idea is to sustain moderate growth of fruit trees and not vigorous growth. Organic N release occurs at the worst time for established fruit trees so excessively rich soil can be a minus in humid regions. Where it doesn’t rain in the summer you can control plant growth by controlling water during the growing season.