Can You Fertilize Trees in Summer? What South Shore Homeowners Should Know

Is It Safe to Fertilize Trees During the Summer?

Fertilizing trees in hot weather can be a gamble. Yes, trees continue to grow during summer, but the stress from heatwaves and potential drought makes them more sensitive than ever. Applying the wrong type or amount of fertilizer — especially high-nitrogen, fast-release formulas — can scorch the roots, promote weak, leggy growth, or even cause irreversible damage.

From our years of working with homeowners across South Shore, we’ve found that mid-summer is rarely the best time to fertilize unless your tree is showing clear, nutrient-deficiency symptoms. At Landscaping by J Michael, we usually recommend a more holistic approach during this season — focusing on soil enrichment, proper watering practices, and organic mulching instead of chemical fertilizers.

In fact, a peer-reviewed study published in the Journal of Arboriculture found that excessive summer fertilization significantly increases the risk of tree stress and pest vulnerability. Our experience backs that up: summer is the time to support your trees, not overwhelm them.

Signs Your Tree Might Need Summer Fertilization

Still wondering if your tree might need a nutrient boost? You’re not alone. Many South Shore homeowners assume all yellowing leaves mean a tree needs fertilizer — but that’s not always the case. Fertilization in the summer should be a response to very specific signs, not a routine habit.

Here are a few red flags we look for before recommending any summer fertilization:

• Slow or stunted growth despite regular watering and sun exposure
• Pale or yellowing leaves (chlorosis), especially in new growth
• Sparse leaf canopy or premature leaf drop during peak growing season
• Weak branching, thin new growth, or dieback at branch tips

These symptoms may indicate a nutrient deficiency, but they could also be signs of deeper issues like poor soil structure, compacted roots, or water stress. That’s why we always encourage homeowners to start with a professional soil test before applying anything to the soil.

The University of Minnesota Extension provides an excellent breakdown of how to interpret tree stress symptoms and how to distinguish between nutrient deficiency and other factors. Knowing the difference helps you make the right call and avoid unnecessary fertilization.

From our experience at Landscaping by J Michael, we’ve seen too many trees harmed by well-meaning but misinformed fertilization. When in doubt, call in a pro — your tree will thank you.

Best Types of Fertilizer for South Shore Soil

Not all fertilizers are created equal, especially when it comes to tree care in summer. Here on the South Shore — with our mix of clay-heavy and sandy soils — you want to make sure you’re feeding your trees with materials that support slow, steady growth, not quick spikes that can backfire in the heat.

For most established trees in the region, we recommend:

• Slow-release organic fertilizers – These release nutrients gradually and reduce the risk of root burn or overstimulation, which is common with fast-acting products in high temperatures.
• Compost or compost tea – These options not only add essential nutrients but also improve overall soil structure, which is key in areas where drainage is poor or roots are struggling to breathe.
• Mulch-based feeding – Using natural mulch like shredded bark or leaf mold around the base of the tree creates a slow-feeding system as it breaks down. This mimics forest-floor conditions and is great for supporting soil microbes and moisture retention.

Avoid fast-acting synthetic fertilizers during summer. These can do more harm than good, especially when combined with heat stress or irregular watering. They tend to stimulate too much foliage growth without giving the roots time to keep up — a recipe for long-term damage.

For an evidence-based look at fertilizer types and when to use them, we recommend reading this practical guide by the University of California Agriculture and Natural Resources. It breaks down the differences in fertilizer types and the impact of temperature and timing on absorption.

At Landscaping by J Michael, we always lean into solutions that match the natural rhythm of your soil and trees — because real, sustainable growth takes more than just a quick fix.

Summer Fertilization Tips and Mistakes to Avoid

Successfully fertilizing trees in hot weather requires more than just spreading product around — it’s about timing, technique, and a little South Shore-specific wisdom. We’ve seen even healthy trees suffer because the fertilizer was applied too aggressively, too late in the day, or at the wrong point in the weather cycle.

Here’s what we’ve found works best when fertilizing trees in summer:

• Water deeply before and after applying any fertilizer to reduce root stress and help nutrients absorb properly.
• Apply in the early morning or late afternoon to avoid evaporative loss and fertilizer burn.
• Avoid fertilizing during or right after a heatwave or drought, when trees are already in a vulnerable state.
• Stick to the recommended dosage — when it comes to summer tree care, less is more.

And here are a few big no-no’s:

• Don’t fertilize newly planted trees in their first summer — their energy should go toward root development, not forced growth.
• Don’t apply fertilizer to dry, compacted, or cracked soil — it won’t absorb correctly and may burn the roots.
• Don’t pile fertilizer near the trunk or across exposed roots — it can cause decay and attract pests.

If you’re not sure whether your tree is ready for summer fertilization, we suggest referencing the USDA Tree Owner’s Manual, a helpful government resource that outlines proper fertilization, mulching, and care practices for homeowners. Pairing knowledge with care goes a long way — and if you need help applying these tips to your own yard, LJM is just a call away.

When Not to Fertilize: Heat Stress and Drought Conditions

Even a well-intentioned dose of nutrients can backfire in the wrong conditions. Fertilizing trees during periods of extreme heat or prolonged drought can actually do more harm than good. When a tree is already under stress, its roots struggle to take up water — let alone process additional nutrients. The result? Fertilizer burn, increased stress symptoms, and potential long-term damage that’s difficult to reverse.

We’ve seen South Shore homeowners unknowingly worsen their trees’ condition during July and August by adding fertilizer when what the tree really needed was water, mulch, and a break. If your tree looks droopy, dry, or wilted during a heatwave, it’s not asking for food — it’s begging for hydration and root zone support.

The best summer tree care approach in these conditions is to focus on improving soil moisture, mulching properly to retain that moisture, and checking the tree’s root system for signs of compaction or rot. You can read more about drought stress and tree care strategies in this guide by the Colorado State University Extension, which outlines how trees react to drought and what not to do when they’re already struggling.

From our years of experience at Landscaping by J Michael, we can confidently say that sometimes the best way to care for a tree is to pause, observe, and allow nature — with a little help from proper watering and soil care — to do its work. Fertilizer is a tool, not a cure-all, and knowing when not to use it is just as important as knowing when to apply it.

Final Thoughts: Tree Health Beyond Fertilizer

Fertilizer isn’t a magic fix — it’s one of many tools in your tree care toolkit. Especially during the hot, dry South Shore summers, the secret to lush, resilient trees lies not just in what you feed them, but how well you understand their environment. At Landscaping by J Michael, we’ve seen firsthand how consistent watering, thoughtful mulching, and good soil preparation often outperform hasty applications of fertilizer when it comes to real, lasting results.

So, can you fertilize trees in summer? Yes, but only when your trees truly need it — and only when done with care, timing, and the right materials. Whether it’s identifying signs of nutrient deficiency, avoiding fertilizing trees in hot weather, or tailoring your plan based on local soil types, taking a personalized approach is always better than following a one-size-fits-all formula.

And if you’re still not sure where to begin, let us help. From evaluating whether summer fertilization is right for your trees to designing full seasonal tree care programs, Landscaping by J Michael is here to help South Shore homeowners give their landscapes the support they deserve — all year long.

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