Fall Fertilization Risks

[Fishin' Rod]

We have planted about 150 trees on our Kansas farm in the last three years. Mostly hybrid oak trees, persimmons, and pear trees. We are located right at the border between Zone 6 and Zone 7.

I have fought the drought for the last two years, and most of the trees have made it through. However, a few of the trees have survived tough conditions but they are just barely hanging on to life. These trees suffered from one of two problems. Most are located in my areas with the sandiest soil. I amended with lots of peat moss before planting, but these soils did not hold as much precious water during the drought and some of these trees suffered drought damage. The other problem is tree damage due to burrowing pocket gophers. I have been watering some of these trees and then had the soil suddenly collapse into a round 1-1/2" hole. I then have to gently tamp the soil with my boot to get the water to pool at the tree. I don't know if the gophers damaged the trees directly by eating through a large percentage of the root system, or if they just made large air pockets around the roots and the tree subsequently suffered because the roots could not reach much water.

For both the drought damage and the gopher damage the results are roughly the same. The main leader of the tree died and a few leaves did manage to survive at the base of the trunk. However, the next spring, these trees did attempt to come back. Some had limited leaf growth at the base of the trunk and some had water sprouts that grew fairly quickly.

Question for the experts:

I did NOT fertilize the damaged trees this spring because they were somewhat stressed. I would like to fertilize them this fall as the summer heat stress and drought is abating. However, none of these trees are healthy and robust. Can I still fertilize them this fall to help the tree with a little late growth, or does that increase my chance of killing the tree this winter since very little of the above ground portion that is living would be woody material that would survive several winter hard freezes?

Thanks for any assistance in this matter. (I know this is not a question with a clear cut answer. Therefore any speculation or ideas from people with more tree care experience would still be greatly appreciated.)


Thanks,
Fishin' Rod

 

[PJM]

Fertilizing trees already under stress will likely only increase the stresses. I never recommend fertilizing until trees are well established, which it sounds like your trees are not. Even when I do recommend fertilizing it is to address a specific nutrient concern and not "just because".

The question is why do you want to fertilize the trees?

Tree Care During Drought
Helping Trees to Manage Stress

 

[Fishin' Rod]

Thanks for the reply PJM. You are asking more succinctly the exact question I attempted to ask!

The trees did not thrive this year and had much reduced leaf coverage for trees of that size and age. I am speculating that not much photosynthesis occurred this summer and the trees are going to send very little glucose to the roots for storage over the winter.

Will fertilizing now still get that flush of new growth and some additional leaves to gather fall sunlight, OR would I just be adding more stress to trees that are already operating under some significant long-term stress? (I think this fall season will NOT be stressful when only considering the expected weather.)

I agree with your rule about not fertilizing trees until they are well established. Some of the trees I refer to above were well-established and have become static now due to damage. Some of the trees never managed to get well established. However, I did lightly fertilize some of my other trees this spring that showed little growth in Year 1 and Year 2, but were vibrant and green. I don't know if you would consider that type of 3 y.o. tree to be well-established or not? Those trees did have a nice response in almost all cases.

I am just trying to perform "best practices" for the poorly performing trees. I am just not expert enough to determine what are the best practices for trees in this circumstance. If the consensus is to NOT fertilize, then I will try to nurse them through another winter and re-evaluate next spring. The poorly performing trees are still in tree tubes.

(Kansas winters are highly variable. We could have our first hard freeze on October 15th, or we could have our first hard freeze on December 5th. Expected first hard freeze is probably around the first week of November.)