Feeding the Summer Garden: A Practical Guide to Fertilizing

By July, gardens in the Boise area are alive with activity. Tomato vines climb their cages, squash leaves stretch across beds, and pollinators hum from blossom to blossom. But while the season’s early work is behind us, another critical task emerges: feeding the garden.

Plants are living systems, constantly drawing nutrients from the soil to fuel growth, flowering, and fruiting. As those nutrients are used up, the soil alone often can’t keep up with the demand—especially in raised beds, containers, or sandy soils common in southern Idaho. Understanding how to fertilize makes all the difference.

This guide walks through the most common fertilizing methods home gardeners use, when and why they matter, and how to apply them effectively.

Side-Dressing: A Midsummer Nutrient Boost

Side-dressing is the practice of applying fertilizer in a narrow band a few inches away from the base of a plant and watering it in. It's especially useful in July for long-season, heavy-feeding crops like tomatoes, peppers, squash, and corn.

In early summer, nitrogen-rich materials (like urea, blood meal, or calcium nitrate) can support foliage development. But by midseason, as plants begin flowering and fruiting, excessive nitrogen can cause more leaf growth at the expense of blooms and harvest.

In July, a better choice is a balanced fertilizer (e.g., 5-10-10) or one higher in phosphorus and potassium to support flowering and fruit development. Organic options include composted manure, bone meal (typically 3-15-0), or natural blends formulated for tomatoes or vegetables.

Fertilizer should be applied 4–6 inches from the stem and gently worked into the soil or covered with mulch. Always water thoroughly after applying.

Top-Dressing: Slow and Gentle

Top-dressing is the process of applying compost or granular fertilizer to the soil surface around plants. It requires no digging and is ideal for leafy greens, herbs, root crops, and perennials—or anywhere you want to avoid disturbing roots.

This method supports soil structure, boosts moisture retention, and releases nutrients slowly. It’s especially well suited for use with compost or slow-release organic fertilizers. Mulching after top-dressing can further improve moisture retention and soil health.

Top-dressing can be repeated every few weeks throughout the growing season, especially after heavy rains or heat waves.

Liquid Feeding: Fast and Effective

Liquid fertilizers are mixed with water and poured around the base of the plant. This method is particularly effective in July when container-grown plants and raised beds may need quicker nutrient access due to faster drying and leaching.

Liquid soil drenches can be made from fish emulsion, compost tea, kelp extract, or water-soluble commercial fertilizers. Apply every 1–2 weeks as needed.

This method is fast-acting and easy to tailor, especially for vegetables like cucumbers, squash, or tomatoes that show nutrient stress mid-season.

Foliar Feeding: Targeted and Temporary

Foliar feeding involves spraying a diluted fertilizer solution directly onto plant leaves. It’s sometimes used to address visible nutrient deficiencies or to support plants under short-term stress.

While plants can absorb some nutrients through their leaves—especially micronutrients like iron, magnesium, or calcium—this method is usually most effective as a supplement, not a replacement for soil fertilization. Effectiveness depends on nutrient type, leaf age, and weather conditions.

Foliar sprays may help:

• Correct specific deficiencies quickly
• Support stressed or struggling plants
• Bypass root-zone issues temporarily

However, they can also:

• Burn leaves if applied in hot, dry weather
• Offer only short-term results
• Increase disease or runoff risk if overused

Apply foliar sprays only when clearly needed, and always during cooler parts of the day—morning or evening. For most gardens, foliar feeding plays a limited, supportive role, best reserved for micronutrient issues or recovery from stress.

Pre-Plant Incorporation: Building the Foundation

Though not a July task, it’s worth noting that much of a garden’s nutrient supply should be in place before planting. Mixing compost and a balanced fertilizer into beds in early spring provides a steady source of nutrients as plants establish.

This early step is especially important for root development and early vegetative growth. Soil testing can help fine-tune what’s needed.

Summary Table

Method	Best Use	Midseason (July) Application
Side-Dressing	Fruiting vegetables	Use balanced or low-nitrogen blends
Top-Dressing	Leafy greens, herbs, perennials	Apply compost or slow-release fertilizer
Liquid Feeding	Containers, raised beds	Every 1–2 weeks with water
Foliar Feeding	Nutrient deficiencies, stress	Use selectively; best for micronutrients
Pre-Plant Mix	All crops	Done at planting; provides base nutrition

Final Thoughts

Fertilizing in July is about balance. The garden is in full gear, and plants need support—but not too much. Focus on what your soil and plants are telling you. Look for signs of deficiency, evaluate past applications, and use the right method for the right crop at the right time.

Fertilizing smart in midsummer can mean the difference between a sluggish garden and a bountiful harvest.

For Additional Reading:

Mid-Season Boost for Hungry Plants

Foliar Feeding

Fertilizing your garden:Vegetables, Fruits, and Ornamentals

Do Plant Brews Really Work? What the Science Says

If you’ve spent any time on gardening forums or social media, you’ve likely come across homemade plant brews like weed tea, compost tea, banana peel tea, and even eggshell tea or Epsom salts. These DIY fertilizers are praised for being natural, cost-effective, and sustainable—but how well do they actually work? Let’s look at what current research says about these popular garden elixirs.

Weed Tea: Free Fertilizer or Just Funky Water?

Weed tea is made by soaking or fermenting common weeds—such as dandelions, chickweed, or comfrey—in water, with the idea that the nutrients weeds extract from the soil will leach into the liquid and feed your plants. While weeds are nutrient accumulators, there’s little published research confirming the nutrient content or effectiveness of weed tea. Some studies on plants like Tithonia diversifolia (Mexican sunflower) used as green manure show benefits when incorporated directly into soil, but not as fermented teas. At best, weed tea may provide a mild boost, but results are unpredictable and largely anecdotal.

Compost Tea: Some Scientific Backing

Compost tea, particularly the aerated kind (ACT), is one of the most researched DIY fertilizers. It’s made by soaking compost (plant-based or worm castings, not always manure) in water, sometimes with added sugars and oxygen to increase microbial growth. Studies have found that compost tea can improve microbial life in soil, help suppress certain plant diseases, and occasionally increase plant growth. However, its success depends on how it’s brewed and applied. Using fully matured, pathogen-free compost is key, especially when used on edible crops. While compost tea shows promise, it’s not a substitute for nutrient-rich compost or balanced fertilizers.

Banana Peel Tea: Some Promise, If Processed Properly

Banana peels are high in potassium and other minerals. Recent studies suggest that processed banana peel fertilizers can improve soil quality and plant growth. For example, a 2024 review published in the journal Agriculture by MDPI discusses the potential of banana peel-based biofertilizers and their effectiveness when properly processed. Other studies support their use in nano-fertilizer or composted forms for boosting yields and plant health. That said, soaking banana peels in water for a few days may not extract meaningful nutrients. Composting them is a far more effective way to return their value to the soil.

Eggshell Tea and Epsom Salts: Popular, but Situational

Eggshell tea is made by soaking crushed eggshells in water to extract calcium. While eggshells are rich in calcium carbonate, it breaks down slowly. Studies show that unless finely ground, eggshells don’t readily release nutrients into water or soil. Composting or grinding them into powder is more effective. Epsom salts (magnesium sulfate) are also frequently used, especially for tomatoes and peppers. While magnesium is an essential nutrient, overuse can disrupt soil nutrient balance. Unless a soil test shows magnesium deficiency, regular use isn’t necessary and may cause harm.

The Bottom Line: Good Garden Practices First

DIY fertilizers like weed tea, compost tea, banana peel tea, eggshell tea, and Epsom salts can be part of a sustainable gardening routine. However, their effectiveness varies widely, and most are only mildly beneficial unless processed and applied properly. Before adding any homebrew fertilizer to your garden, remember: healthy plants start with healthy soil. Compost and organic matter are your foundation. Always test your soil before adding amendments, it’s the only way to know what your plants actually need. Use DIY fertilizers as supplements, not substitutes, for a well-balanced approach.

Spring Soil Prep - What you can do Now! (or as soon as the ground thaws :>)

The best way to begin preparing your soil is with a soil test. 

Your local University of Idaho Extension office can help you with this. This test is a great place to start because it tells you what to add to your soil to help your garden perform better. 

soil sample probe

Organic soil amendments also provide an important source of nitrogen for your plants.  Till or turn under with a spade 3-4 inches of compost into your soil at a depth of 6-8 inches and rake your bed smooth.

With a soil sample probe, the task is much  easier... and worth the cost - since you'll probably check your soil many times over the years.

This video shows how to gather your soil sample.

The most important thing you can do for your garden’s soil is to add organic matter. Organic matter aids in drainage and minimizes soil compaction, which reduces soil oxygen.

When choosing an amendment, consider carefully what you use. Animal based products and bio-solids are high in salts and heavy metals which build up in your soils. Consider using well aged plant based compost instead.

Now...check your plant temps, and frost days and...enjoy planting!