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All About Vermicast

Updated: Apr 27, 2021

100% freshly harvested vermicast

Vermicast, the wondrous mixture of worm castings and organic matter harvested from worm beds, has almost too many benefits to list! But always up to a challenge, we will attempt to extol its innumerable virtues and outline best practices to get the most from your worm poop.

Why it works

When you add vermicast to your soil, you help the soil absorb and retain moisture. The organic matter in vermicast helps the soil particles clump together, improving soil structure.

Vermicast contains myriad nutrients that are plant-available and released gradually into the soil.

Vermicast has a relatively low carbon-to-nitrogen ratio, making nutrients more available to plants and helping them to grow stronger and faster. The C:N ratio of vermicast typically falls in the range of 10:1 - 20:1.

Ideally vermicast has a neutral pH, so it will not burn plants and helps create a perfect environment for all the right microbes and fungi to thrive.

Vermicast contains beneficial acids (humic and fulvic) which work by dissolving otherwise insoluble minerals, stimulating plant growth.

One of the most beneficial values of vermicast is its microbial properties. Vermicast boasts a large and diverse population of microorganisms including beneficial mesophilic microbes that help with suppressing diseases.

Phenolic compounds in vermicast help to repel garden pests - either by their bitter taste or downright toxicity - through uptake in the root system (warding off caterpillars, aphids and spider mites). Studies have also shown that vermicast promotes the growth of certain fungi that suppress parasites!

How much?

Bear in mind, a little vermicast goes a long way! In fact, there are studies focused primarily on optimal amendment ratios. Adding vermicast to soil works best when 10% - 40% by volume is added, with optimal values varying depending on the plant and its growth/flowering stage. Over 40% volume can have negative impacts, including depressed growth, so no need to overdo it.

Our house-made potting mix contains vermicast, compost, sand, and soil

When creating a potting mix, we use about 20% vermicast and 20% compost mixed with our regular Hanover County (loamy/sandy) soil. This works well for potted plants and container gardens. For new garden beds, we typically throw a handful of vermicast into the planting hole. For existing garden beds we top dress individual plants with about 1/4 cup per plant.

When to use

The benefits of vermicast can be seen from seed germination through flowering and fruiting. It's never too soon to start adding vermicast to your soil. Add it to your seed starter mix to help seeds germinate faster and to create a strong, healthy root system in your seedlings. Mix vermicast into the planting hole when transplanting into the ground. For existing gardens, top dress plants every 2-3 months.

How to store

We store our vermicast in bulk and bag it to order. At packaging, it will contain 40% - 50% moisture content and its consistency will be moist and loose with fine particle clumps (see top picture above). If you do not plan to immediately use all of your vermicast, store the package in a cool, dry place away from sunlight. Leave the bag slightly open or poke holes at the top to allow passage of air, but not enough that it loses its moisture through evaporation. If moisture content drops precipitously (to <35%), the product will become dusty and difficult to apply - this also means the microorganisms have expired. When properly stored, vermicast will retain its benefits for 18 - 24 months.

Herb plugs using our house-made potting mix

It's fool proof!

There's virtually no downside to using vermicast! So consider adding vermicast to your soil if you want any of the following benefits:

- Help soil absorb & retain moisture

- Improve soil structure

- Aid in the growth and proliferation of microbes

- Encourage root growth

- Allow plants to more effectively utilize and retain nutrients

- Help suppress disease and fight off pests

Our vermicast is typically available year-round and comes in 4 & 12 qt resealable bags. We test C:N, pH, N-P-K, and EC to ensure quality. Contact us if you have any questions about obtaining, using or storing vermicast.

Until next time, happy gardening!


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