Summer Tree Care: Fertilizer Tips to Strengthen Trees Before Fall

As summer progresses, trees face increased stress from heat, drought, and pests. Whether you’re maintaining ornamental trees in a residential landscape or managing fruit or shade trees on larger properties, summer fertilization is a vital—but often overlooked—part of long-term tree health.

Fertilizing trees in mid to late summer helps support photosynthesis, strengthen root systems, and store nutrients for the months ahead. But choosing the right products and application methods is key to avoiding overfeeding or promoting weak late-season growth. In this blog, we’ll walk through the strategies that work, including top products from Supply Solutions LLC that keep your trees thriving.

Why Trees Still Need Fertilizer in Summer

While spring is a common time to fertilize trees, summer applications provide key mid-season support. As the canopy expands and soil dries out, trees require:

• Steady nitrogen to support ongoing foliage health
• Micronutrients like iron and magnesium to prevent chlorosis
• Balanced nutrients for root strength and water uptake

Summer is also when nutrient deficiencies become most visible:

• Pale green or yellow leaves (especially in newer growth)
• Early leaf drop or browning edges
• Stunted canopy growth or poor branching

Best Summer Fertilizers for Trees

1. 12-6-6 Ornamental Fertilizer

• Designed for trees, shrubs, and woody ornamentals
• Promotes slow, steady vegetative growth without overstimulation

2. 10-10-10 with Micronutrients

• Ideal for mixed tree plantings or fruit trees
• Delivers balanced NPK plus essential micronutrients like zinc and iron

3. Ammonium Sulfate 21-0-0-24S

• Useful for alkaline soils where nutrient lockout is common
• Supports deeper green foliage and improves nitrogen uptake

Application Timing & Methods

• Apply in early morning or late afternoon to reduce stress
• Water trees well before and after fertilizing
• Apply granular fertilizer at the dripline, not near the trunk
• Liquid fertilizers can be used for foliar feeding in severe deficiency cases

How Much Fertilizer Do Trees Need?

A general rule for granular applications:
0.1 to 0.2 lbs of nitrogen per inch of trunk diameter

For example, a tree with a 10-inch trunk should receive 1 to 2 lbs of actual nitrogen spread evenly around the root zone.

Fruit Tree Considerations

• Mid-summer feeding improves fruit size and finish
• Avoid excess nitrogen late in the season—it can reduce fruit quality
• Use 10-10-10 at half strength for young trees

Avoiding Over-Fertilization in Summer

• Don’t apply too close to dormancy (after mid-September)
• Avoid high-nitrogen fertilizers for mature ornamentals unless signs of deficiency are present
• Skip fertilizing drought-stressed trees unless they’re being irrigated

Other Summer Tree Care Tips

• Mulch around the base (2–3 inches thick, not touching the trunk) to conserve moisture and regulate soil temps
• Water deeply but infrequently, especially in compacted urban soils
• Prune lightly to remove dead wood but avoid heavy cuts in summer

Final Thoughts

Summer fertilization is one of the best ways to ensure your trees stay strong, disease-resistant, and prepared for the transition into fall. The right product, applied at the right time, can make the difference between a struggling tree and a thriving one.

Need personalized recommendations for the trees in your landscape? The experts at Supply Solutions LLC are here to help.

Call 503-451-1622
Email sales@mysolutionssupply.com
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Let Supply Solutions LLC help your trees stay healthy and resilient through the hottest months of the year.