Interbay Mulch

When you put your garden to bed for the winter, that doesn't mean nothing happens during the dark, cold, or snowy months. Left bare and exposed to the elements, important nutrients will wash away, and soil organisms will go dormant or even freeze to death.

There are many ways to over-winter your garden while at the same time improving the soil for a head start next spring. One way to invest in your beds was invented at Seattle's Interbay P-Patch: Interbay Mulch.

While similar to sheet composting or Lasagna gardening, Interbay Mulch attempts to bring critters responsible for decomposition all the way to the top layer of organic matter. The full distribution of organisms makes this composting method somewhat faster than sheet composting.

Making Your Mulch

Once your beds are cleared of this season's crops, create a mix of equal parts greens (grass clippings, coffee grounds, fresh chopped plants, composted manure) and browns (fall leaves, non-pressure treated sawdust, dry plant material, etc.) just like you would for a hot compost pile. Though it's tempting to use mostly browns, thinking there's plenty of time for them to break down, be sure you add enough greens for a balanced decomposition process.

Spread your mix in a good foot-thick layer (or more if you have the stamina) on your planting beds. Water the mixture well to wet it down, then cover it all with a layer or two of burlap bags. Wet down the burlap too (or soak the bags in water before placing them). The burlap keeps the mulch dark, damp and insulated so organisms can work all the way to the top of your batch.

That's all there is to it! During the winter, check your mulch every few weeks to be sure it's still slightly damp. You might also turn your mulch at least once during the winter.

Room and Board

Gardeners have experienced a few problems with Interbay Mulch. During the chilly winter months, mice or rats sometimes set up house in the mulch as it retains a bit of warmth under the burlap blankets. If you've incorporated kitchen scraps into the mulch, rodents may not even have to go far for food! You can minimize this problem by excluding food waste from your mulch, and checking under the burlap for rodents every few weeks.

Moist burlap also provides the kind of environment slugs just love! During your occasional winter bed checks, pick out any slugs and kill them.

After a few years of experience, several gardeners at Interbay have noticed that too much organic material can cause their beds to shed water in the dry months. Interbay Mulch may not be appropriate to use every winter. Next winter, plant a cover crop where you had mulch this year. Then rotate back to mulch the year after that.

In the Spring

By the time spring rolls around, your Interbay Mulch will be finished. A few weeks before you're ready to start planting, remove the burlap and turn the beautifully decomposed mulch into the soil. You'll notice a better response from your vegetables and flowers next year as your investment this winter pays off!

More Reading

Here are two great articles about Interbay Mulch on the web. Read them for a more detailed history and additional recipes.

Interbay Mulch at GardenWeb

How to bake a batch of compost at The Christian Science Monitor

Copyright © 2003 Brian Ballard. All rights reserved.