June Fertilization Guide:
Annuals, Perennials, Trees, Shrubs, and Roses
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As summer arrives and gardens burst into color, June is a crucial month to give your plants the nutrients they need for strong growth and vibrant blooms. Here’s our expert, step-by-step guide to fertilizing your annuals, perennials, trees, shrubs, and roses for a thriving summer display.
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Annual flowers and vegetables pour their energy into a single season, so they need a steady supply of nutrients. Whether you’re growing colorful zinnias or juicy tomatoes, regular feeding helps keep your plants healthy, vigorous, and productive.
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- Mix a slow- or continuous-release fertilizer into the soil at planting time.
- For annual flowers, use a water-soluble fertilizer every third watering.
- To get show-stopping blooms, pick a fertilizer that is higher in phosphorus. Of the three numbers on the container of fertilizer, the middle one should be highest. For example: 10-20-10 or 1-4-2.
- For vegetables, use a balanced water-soluble fertilizer once a month.
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Perennials return year after year and may benefit from a nutrient boost for growth and repeat blooms, but they don’t need as much feeding as annuals. In fact, perennials that are light feeders, including many of the natives, do best without any extra fertilizer at all. However others are heavy feeders, like astilbe, clematis, daylilies, hardy hibiscus, lilies, mums, peonies and phlox. These plants reward regular feeding with abundant flowers.
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For perennials that are heavy feeders:
- Top-dress with compost in early spring to provide ongoing nutrients and improve soil structure
- In June, provide a balanced fertilizer (such as 10-10-10) at half strength. Alternatively, use a slow-release fertilizer formulated for perennials at full strength.
- Stop fertilizing perennials in late summer to avoid tender growth that won’t harden before winter.
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- Evergreens may be fertilized in a similar way to heavy-feeding perennials.
- Feed early in spring, and feed lightly a second time in early summer.
- Use a fertilizer formulated for evergreen plants, or a balanced fertilizer (10-10-10, 14-14-14, etc.)
- Many of the broad-leaved evergreens, such as holly, rhododendrons and azaleas, especially benefit from an acidifying organic fertilizer such as Holly-Tone.
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While mature trees and shrubs in healthy soil may not need fertilization, young plants benefit from a summer boost.
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- Fertilize once, either in early spring, or in early summer.
- Use a slow-release fertilizer for trees and shrubs, applying according to label directions.
- Skip fertilizing during drought or extreme heat—plants under stress can be harmed by extra nutrients.
- Fertilize the first three years, or until trees and shrubs become large and well-established.
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Roses are heavy feeders! Regular nutrients mean lush foliage and armloads of blooms.
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- After the first flush of blooms, (about mid-June,) feed with a slow-release, balanced fertilizer (10-10-10 or 12-12-12) at half strength, or an organic rose fertilizer at full strength.
- Using a gentle organic fertilizer or applying fertilizer at half strength lets you feed more frequently without risking over-fertilization, ensuring your roses get steady nutrition without the danger of salt buildup or root damage.
- Continue monthly feedings through July and August, but stop by mid-August so your roses can prepare for dormancy.
- Mulch and add compost for steady, organic support.
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- Surface-applied fertilizers can lose up to 40% of their nitrogen to the air through a process called volatilization, especially in warm or wet conditions. To avoid this, gently work the fertilizer into the top few inches of soil after you apply it. This simple step helps keep valuable nutrients right where your trees and shrubs can use them, and it’s better for both your plants and the environment.
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- Fertilize in the early morning or late afternoon—never during the heat of the day.
- Always water before and after applying fertilizer to protect roots.
- Less is more: over-fertilizing can stress or damage plants.
- Organic fertilizers are gentle and effective, especially in hot weather.
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A well-timed June feeding sets your garden up for a summer full of color and healthy growth. If you need the right fertilizer or want advice tailored to your landscape, get in touch, or stop by Plant Pharmacy at Hoerr Nursery. We carry a carefully selected range of fertilizers and soil amendments—both organic and conventional—to suit every garden. Our knowledgeable staff is always ready to answer your questions, help you choose the best products, and guide you on proper application techniques for healthy, thriving plants. Bring your questions, photos, or even a plant sample, and let us help you grow with confidence.
Happy gardening!
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