How much worm castings should I use?

For most garden beds, incorporate worm castings at 5–20% by volume into the top few inches of soil. For container plants, mix 10–25% into potting soil. Smaller amounts can be applied as a top dressing during the growing season.

Can worm castings burn plants?

No. Properly matured worm castings are low in soluble salts and release nutrients gradually, making them safe for seedlings, transplants, and established plants.

Are worm castings better than compost?

Worm castings are often more biologically concentrated than traditional compost, typically containing higher microbial activity and more plant-available nutrients.

Do worm castings replace fertilizer?

Worm castings improve soil biology and nutrient availability. They may reduce reliance on synthetic fertilizers but are commonly integrated into a broader soil fertility program.

organic gardening Archives

Growing Tomatoes in East Contra Costa County: Tips for Bigger Harvests

By Delta Worms | May 11, 2026

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Top 5 Mistakes Gardeners Make in May (And How to Avoid Them)

By Delta Worms | May 3, 2026

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By Delta Worms | May 3, 2026

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How to Prepare Your Garden Soil for Spring Planting in California

By Delta Worms | March 23, 2026

April Growing Tip for Bay Area Gardeners Spring arrives early in California, and knowing how to prepare garden soil for spring in California is one of the most important steps for a productive growing season. In the Bay Area, soil conditions are already shifting into active growth by April, making this the ideal time to…

Why Add DW Vermicompost to a Seed Starter Mix?

By Delta Worms | February 1, 2026

DW Vermicompost in a seed starter mix can make the difference between weak seedlings and strong, resilient plants. Starting seeds is one of the most hopeful moments in gardening—tiny seeds, big potential. But strong seedlings don’t happen by accident. The soil you start with matters, especially in the SF Bay Area, where cool springs, variable…