New research indicates fertilizing trees and shrubs about a month after a killing frost is ideal
I love gardening for a lot of reasons. I enjoy the fresh air, physical activity, mental stimulation, constant change and more. The fall season is a great time to become reinspired to get outside and do some important maintenance in the garden and landscape. Big dividends in future seasons are the added reward.
One of my favorite parts about gardening is that I’m always learning. Fortunately, I learned something recently that changed my approach to when I fertilize established trees and shrubs.
For most of my gardening life, trees and shrubs that needed a nutrient boost got their annual fertilizer application in early spring, right before active growth began for the year. This timing has been the generally accepted practice by gardeners and experts everywhere for years. And although early spring is a good time, new research indicates there is an even better time.
Contrary to traditional wisdom, many experts now consider late fall, or about a month after the first killing frost, to be the ideal time for applying fertilizers. We now know plants utilize nutrients throughout the year in different ways.
In the past, the most common reason against fertilizing in the fall was the fear that plants and trees would put on new growth if unseasonably warm weather returned, only to be burned or damaged by imminently colder temperatures.
They key is to understand the difference between early fall and late fall timing. If you fertilize in late summer or early fall, when temperatures are still warm and plants are still actively growing, it is likely new growth could occur and damage to tender new foliage could be the likely result.
The rationale for late fall fertilization makes sense when you understand why. At this time, deciduous trees and shrubs have lost their foliage for the year and active growth of plants and trees has slowed. Rather than put on new foliage growth, the roots of established trees or shrubs take the nutrients from the soil and apply them to important health-promoting functions, such as disease resistance and root development. The excess nutrients are stored in the roots and become immediately available when needed for new growth in spring.
However, keep in mind, not all established plants and trees are candidates for a regular fertilization program. I always suggest a soil test be obtained through your local county extension office. Simply gather up a representative soil sample around the area where your trees and shrubs are growing. Be sure to inform the extension service you would like to have the soil tested for this.
The report will let you know what nutrients may be lacking in your soil for optimum growth. The report will also suggest the proper type and amount of nutrients to add.
A common mistake, and not just with trees and shrubs, is to assume fertilizer can and should always be added, and if a little is good, more is better. Nothing could be further from the truth. Excess nutrients are wasted and can end up contaminating the soil, and the environment beyond.
Plants and trees are far more sophisticated then we give them credit. In simple terms, they have built in clocks, timers, calendars and monitoring systems that don’t require our meddling nearly as much as we think, just like with fall fertilization.
About Joe Lamp'l
Joe Lamp'l is the Host and Executive Producer of the award winning PBS television series Growing A Greener World. Off camera, Joe dedicates his time to promoting sustainability through his popular books, blog, podcast series, and nationally syndicated newspaper columns. Follow Joe on Twitter
Joe, I live in north central Illinois and have about 20 burning bushes planted about 3 years ago. They are only about 3 ft. high now and I’m wondering if there is anything I can use to stimulate faster growth. Will a fall fertilizer help? Thanks for any help.
You can use a fall fertilization and plants will store those nutrients until spring. Just don’t apply more than is what is suggested on the packaging. I use organic options that are non-burning. Synthetic options including all-purpose 10-10-10, for example, can work well but they will burn your plants if you use even a little more than suggested. Be careful!
I have a 100+year old ?Southern Magnolia which is beginning to have problems, i.e. loss of leaves and showing its age. Fertilizer has never been applied to it. would it be appropriate to apply fertilizer this fall?
Bill, I don’t think fertilizer is the primary issue but if you are serious about saving the tree, it’s worth it to hire a Certified Arborist to inspect it. And be sure you are getting an actual Certified Arborist. Google them for your area but Bartlett Tree Service and Davey Tree Service are large companies that may serve your city.
my hydranges have not had flowers four five years what can i do and have gotten smaller every year
Don,
It’s hard to know. Are they the mophead selections? Have you tested your soil?
I would recommend a soil test with your local Extension Service (through the University system).
If the plants get smaller each year, you must not be pruning them. Would it be a deer problem? Your plants want
to be watered on a regular basis but make sure the soil drains well. A 1/2 inch layer of mulch (keep it away from the stems) is also a good idea. As for the light, bright, indirect light is best. In dense shade they will not thrive. I hope this helps you get started on figuring out why your hydrangeas aren’t blooming. Best of luck.
Please advise,I have Myers’s lemon trees and other citries trees,there is dease attic the new
Groth the leaves are covered with A Christlize substance what should I use.
You could try mild liquid dish soap and water to wash off the leaves
contact your local hardware store for the insecticidal soap or oil spray. Follow the directions carefully regarding application,
and don’t apply any chemicals if temperatures are over 90 degrees.
Joe,
Hurricane Matthew took out virtually all (19) of my tall pine trees. I am left with some water oaks that weren’t crushed, but they are slender understory trees with sparse foliage. Will they develop into normal looking oaks without competition for light and nutrients? I have pruned off damaged limbs and kept the trees watered. They have not dropped their leaves yet, so should I do anything else or wait for spring. Second question: How do you feel about Milorganite to feed trees? I have used try spikes in the past because they deliver nutrients below the surface, but i gather that you are not a fan.
Hi Wayne. I suspect your water oaks will now perform much more like they were intended to grow in absence of competition from the pines. They should fill out nicely on their own over time. No need for you to do anything else. However, if you want to apply some milorganite, that would not be a bad idea to apply next spring. And I am not a fan of tree spikes since they cannot deliver nutrients over the entire root zone. Applying granular fertilizer broadly on the surface around the drip line is a better way to deliver nutrients to all the roots.
I planted 13 Lelands to make a privacy fence between neighbors, in June 2016. I love the trees!! Is there anything I can fertilize them w/ now that we’re in Dec. ? Or should I do watering still? Or just let nature do her thing until Spring? I want to help them grow nice as much as possible!
Thank you!!
Laura
PS. I am in Virginia. 75 miles west of Washington DC
Hi Laura. Don’t do anything now. Nature will provide all that’s needed. Next spring you could apply a conservative amount of slow release fertilizer or a 10-10-10 all purpose choice. But be very carful with this latter option as you can easily burn your trees and kill them by applying too much. Suffice it to say, more is not better. And with Lelands, they grow so quickly on their own, most people don’t do anything fertilization-wise once they’re planted.
I read several of the questions regarding fertilizing trees. We live in the country about 50 miles north of Los Angeles. It can be warm here in March or cold. Even freezing at night. I used fertilizer stakes last year in early spring with good results. Should I try doing that now – late fall?
No Char. Wait until the spring growing season again. And I would suggest if you do anything, use a slow-release fertilizer applied around the entire drip line so fertilizer is applied evenly to all the roots. Fertilizer spikes have no way to distribute nutrients to all the roots.
We have fruit trees as well as shade trees. Any suggestions to what fertilizer would work best?
I currently have deep root feeds done by a professional. The product used is Mycrohyza. How do u feel about this product and are fall feeds recommended, when do I feel the best time of the year would be?
This is topic is one that is often debated between those that provide this fungal additive to products or soil, and the academic community that nearly universally says that mycorrhizal fungi is already present in native soil and not a necessary additive. If the native soil conditions are conducive, a mycorrhizal association will already be present. But according to research, simply adding it does not create an environment that allows it to remain.
What is not in controversy is the benefit of mycorrhizal fungi. So having it in your soil is excellent for roots. There is plenty of research out there on the web if you want to read more about the pros and cons of paying to add it to your soil.
In coastal areas when should I fertilize a maple tree Ive been told is diseased.
First, do what you can do determine what is causing the disease and try to fix that problem. Then improve the environmental conditions naturally. When you get to fertilization, at this point, I would wait until spring with the tree begins active growth again.
A tree service says one of my very established sugar maples that they pruned considerable dead branches from is in trouble. They want to drill holes in the base every six inches and inject food/nutrients . This cost $300.00. I am not sure of this procedure nor that spring is the right time ?
Hi Richard. While this can be a short term fix, I consulted with my Certified Arborist contact specifically on your question. We agree, the best way to deal with this problem is to address the source problem, which is likely in the soil. The purpose of injecting nutrients into a tree is not the best long term solution. Plus, you open up the tree to additional wounds that can lead to other problems. So the best solution would be to get a soil test from your county extension service. Then treat the area based on the suggestions in the report. The nutrients you should be using based on the report should be a high quality, slow-release fertilizer, like Osmocote. Not the easiest to find locally so you may have to order it. A quick fix but only good, in the good-better-best recommendation is to use an all-purpose fertilizer like 10-10-10 around the drip line. But again, slow release is a much better option.
Great advice, I had little problems with tree fertilization, this helped me so much.
Do you approve of using a product like Ironite in the fall?
Bob, I would wait until spring or when your lawn begins its active growth period again, assuming you live in an area where grass has a dormant or semi-dormant period. Also, I would do a soil test first. Iron is usually present in quantities sufficient for grass, but can be inhibited by soil pH. So, I think the best use of your time and resources is to first do the soil test, then see if iron is needed at all, and if so, add ironite during active growth period like next spring or summer depending on the type of grass that you have.
When do fertilize shrubs that bloom in the fall and winter?
Fertilize during active growth Carolyn. So spring and mid summer would be good. That’s all I would do. They store energy and nutrients and use when needed.
Can you please advise me on what kind of ‘all purpose’ fertilizer I can use on my trees. To have someone come in to do it is costly. Also the best way to apply it.
Thank you!
Numbers on a fertilizer bag or package that are equal, such as 10-10-10 or 13-13-13 have equal amounts of the primary nutrients are considered all-purpose. You can find these products at nurseries and garden centers of box stores. On average, a 40 lb. bag should cost you around $15-$20. Follow the directions on the package to know how to distribute and how much. Generally, you are spreading it lightly around the drip line (the perimeter of your trees where the branch tips end) of your trees.This is were most of the feeder roots are that will take up the fertilizer.
Do you have a recommendation for a fertilizer that I can buy from the local home improvement store? I just finished applying a winterizer to my yard which is around all the trees we have. Is that sufficient? I also have some shrubs that do not get this and I need to treat them separately.
Thanks for any advice you may have.
Robert
I would use an all-purpose fertilizer around trees and shrubs. Such products have equal amounts of each of the primary nutrients (nitrogen, phosphorus, and potassium). Examples that you can find in box stores are: 10-10-10, 13-13-13, etc. The higher the number, the more of each nutrient is contained in the package by weight. Winterizer fertilizers designed for lawns are typically too weighted towards the first and last numbers in the analysis, so the balance is lacking. The bottom line is, that although trees and shrubs will also benefit from the winterizer, if the first number in the analysis is too high, you could stimulate too much late season growth, which you don’t want to do. For future applications, go with a balanced, all-purpose formulation for trees and shrubs.
What are your thoughts on fertilizing with tree & shrub fertilizer spikes? Like Jobes or Winchester Gardens?
There’s no question they work for the area where the fertilizer is able to reach the roots. I like this method to keep the fertilizer contained to reduce runoff and deliver a steady supply of nutrients over time through controlled release. However, my issue is that the fertilizer is very contained around the area of the spikes. How far does the fertilizer spread? Not very. Tree and shrub roots go around the plant 360 degrees, yet the spikes can’t cover that much area, especially on trees. Most feeder roots are close to the surface. And how far out do the tips really go? You can guess but if you are too far out or too close, you miss the tips of the roots that take up the water and nutrients. It’s a guessing game. If it were me, I would broadcast the fertilizer around the root zone, out to the drip line and beyond. Yes, you will use more fertilizer, and there will be runoff (which I don’t like), but if you are trying to fertilize trees and shrubs, you need to get the nutrients to wherever the roots are.
Joe,
Is it safe to give the trees a healthy dose of compost tea around the drip line/circle of a tree? I’ve been doing this when I spray my lawn with compost tea and it seems my trees (all young trees) are responding well.
Thanks for your help,
Dave
Hi Dave. I can’t imagine a time when adding compost tea is ever bad. Keep doing what you’re doing. You’re trees are telling you they approve!