When people think about fertilization, they often consider their gardens, but rarely their trees. However, trees greatly benefit from regular fertilization, providing nutrients that allow them to grow larger, healthier, and more vibrant. Understanding the proper season for fertilizing your trees and the associated benefits is important for keeping your trees healthy.
In this article, we will look at the benefits of fertilizing during different seasons. We’ll also examine why we fertilize trees when we do and look at times you should avoid applying fertilizer to your trees. We’ll also cover proper nutrient application methods to prevent harming your trees.
Key Takeaways
- Fertilize trees to supplement missing nutrients in the soil, not indiscriminately.
- Apply nitrogen fertilizers in spring to fuel growth during the season.
- Summer fertilization should exclude nitrogen to avoid promoting too much new growth before winter.
- Fall fertilization should happen at the end of the season to give the roots time to absorb and store nutrients for following spring.
- Apply winter fertilizers at the end of the season when the ground isn’t frozen.
PRO TIP: Have an arborist conduct a soil test before applying any fertilizer to your trees. A soil test will determine what specific nutrients the soil lacks, and you can create a targeted fertilization plan with this information in mind. Our team at Clauser Tree Care can develop a fertilization plan tailored to your trees and soil conditions.
Spring Fertilization for Trees
Spring is an ideal time for fertilization when timed and applied properly.
Trees respond well to spring fertilization as it gives them a kickstart and supports new root growth, allowing them to grow more vigorously.
We typically recommend applying fertilizers in the early spring months, as trees emerge from dormancy. Early in the year, trees are typically looking for a supply of the three main macronutrients – nitrogen, phosphorus, and potassium – that are found in most fertilizers. A boost of these nutrients helps a tree as it exits dormancy and prepares for the growing season.
Opt for slow-release fertilizer formulas, which provide sustained nutrition rather than an immediate surge.
Determining the proper amount of fertilizer to use, and which types of nutrients, should be based on soil test results indicating whether there are any nutrients lacking in the surrounding soil. Many established trees and shrubs won’t need supplemental nutrients every year, particularly if you mulch the area with
compost or organic matter. The exceptions are fruit trees, where yearly fertilization has numerous benefits. As a rule of thumb, the University of Massachusetts Extension recommends you apply one to three pounds of nitrogen per 1,000 square feet of surface area.
Spring Fertilization Concerns
While spring is one of the best times for fertilization, there are also concerns you should keep in mind to avoid damaging your plants.
Avoid high-nitrogen, quick-release fertilizers that encourage excessive growth. Tender new growth is more susceptible to pests and diseases, and spring and summer are when we often see most of the pest activity and disease spread in Pennsylvania. Stick with lower nitrogen fertilizers that will encourage more sustainable growth.
Newly planted trees generally do not need fertilizer. Arborists typically don’t recommend fertilizing trees for the first few years after transplanting as it can damage young roots.
Be cautious about applying a “balanced” fertilizer (where the amount of nitrogen, phosphorus, and potassium are the same, such as a fertilizer labeled 10-10-10). While nitrogen quickly moves through the soil, the other two nutrients do not. So, if you apply enough fertilizer year after year to supply the nitrogen needs of your trees and shrubs, you’ll quickly end up with too much phosphorus and potassium in the soil.
PRO TIP: Fertilizer should be something you use very carefully and sparingly. In many instances, less is more, as too much can stress or even kill a tree. Excess fertilizer can burn a plant’s roots and leave it in worse shape than when you started. Never use more than the recommended amount on the package unless a soil test indicates it’s necessary.
Summer Tree Fertilization in Pennsylvania
Summer fertilization offers benefits for your trees but requires care.
While trees still benefit from the main three macronutrients (nitrogen, potassium, and phosphorus) during summer, limit the amount of nitrogen you supply. Mistiming nitrogen application or using too much will encourage growth when you don’t want it and leave your tree vulnerable to winter damage. Trees will also need less phosphorus in the summer, as the nutrient primarily assists with root growth and development.
Focus instead on potassium, calcium, magnesium and micronutrients like iron, manganese, zinc, cop-per, boron and molybdenum, using only the amounts recommended by soil test results.
Overall, use smaller amounts when applying fertilizer in early summer, don’t overfocus on one nutrient, and keep nitrogen to a low level.
Fertilization methods we recommend in the summer include foliar sprays (applying nutrients directly to the leaves), soil application, and fertigation (combining irrigation and fertilization).
Avoiding Common Summer Tree Fertilization Mistakes
Avoid late summer fertilizer applications, especially high-nitrogen products, unless an arborist recommends it.
Never fertilize a tree that appears stressed or if we’re experiencing drought conditions. Trees cannot properly absorb nutrients without water, and fertilizers may damage tree roots if applied during a drought.
Summers in Pennsylvania can be dry and drought conditions can develop, so keep an eye on the Pennsylvania Department of Environmental Protection’s website for announcements of droughts in Bucks and Montgomery counties.
Late fall is often the perfect time to apply fertilizer to your trees to prepare them for the next season.
Fall Fertilization: How it Benefits Pennsylvania Trees
Fall, like spring, is ideal for tree fertilization. You will want to wait until late fall to apply any fertilizer to your trees, and we generally recommend waiting until one month after the first killing frost (typically in late October or early November).
Fall fertilization allows roots to absorb and store nutrients, preparing trees for energized spring growth while avoiding pre-winter stress.
We recommend using a slow-release fertilizer in the fall with a focus on replenishing any nutrient deficiencies identified by a soil test (other than nitrogen!). This provides steady nutrition without spurring new growth just before the tree enters dormancy.
Fall Fertilization Don’ts
If you choose to fertilize in the fall, you will want to avoid two things:
- Avoid quick-release and high-nitrogen fertilizers which encourage tender new growth susceptible to winter damage.
- Don’t fertilize too early in fall as it disrupts the tree’s transition to dormancy.
PRO TIP: Fast-release fertilizers are water-soluble, quickly providing nutrients to the tree’s roots when watered into the surrounding soil. They can provide immediate benefits, but only when used at the right time.
Winter Tree Fertilization: Drawbacks and Benefits
While unconventional, late winter fertilization (just before spring) supplies nutrients for root growth simi-lar to early spring applications, giving your tree a jump-start on the season.
In the winter, you may want to opt for a deep-root fertilization program to ensure the nutrients go directly to the roots. A slow-release fertilizer will also be beneficial to ensure a steady nutrient supply throughout the year.
Concerns With Winter Fertilization
Early winter fertilization is generally not recommended. Instead, wait until late winter just before spring arrives.
Avoid fertilizing when the ground is frozen, as nutrients can’t penetrate the soil or be absorbed by tree roots, resulting in wasteful runoff that may contaminate water sources. Wait until the ground thaws in late winter and there’s no risk of imminent refreezing before applying fertilizer.
Partner with Clauser Tree Care for Proper Fertilization
Tree fertilization requires a strategic, tailored plan – incorrect timing or fertilizer amounts often prove more detrimental than forgoing it entirely.
The arborists at Clauser Tree Care test your soil to determine nutrient needs and then develop a customized fertilization plan to ensure your trees receive exactly what they need to thrive each season. Call us at 215-542-8291 or request a quote online to learn more about our services and schedule an appointment.
About Clauser Tree Care
From who you talk to on the phone in our office, to our courteous and experienced work crews who provide your service, all of the hard-working team members at Clauser Tree Care strive for complete client satisfaction. Our job is simply not done until you are pleased with the experience that you have had working with our company. Founded more than 25 years ago on the principles of honest work and arboricultural best practices, we strive for a higher standard of care for a greener future.
