Friday, July 18, 2008

Compost Q&A

Here are some compost questions from astute readers.

Q. What do we do with garden waste that isn't applicable for chopping up and putting back in the garden, like sticks, raspberry shoots, noxious weeds and the like?

A. Believe it or not, you can put most any plant material in a hot compost pile! Temperatures in piles I've described here can reach as high as 160 degrees F. That's enough to kill most bad bugs, weed seeds, and pesky roots. However, our reader is right: some stuff just should not be put back in the garden, especially plants suffering from viral infections. Bag infected plants and throw them away with your regular household trash. Any old wood (like stakes or raised bed boards) should also be thrown away as they'll simply take too long to compost.

Q. Are there 'manual' options to using a chipper/shredder? It would be nice to know if one could get garden waste and "browns" ground up nice and fine like the shredder does, without messing with a machine. Manual chopping doesn't really do the trick.

A. Mercifully, it's not necessary to chop everything super-finely for compost. If you can get your plant material chopped to about 3" sections or shorter, and bruise the tougher stuff, then enough critters and fungi will get access to break down the material. I like to step on sunflower or corn stalk sections, partially rotten onions or garlic, and tomatoes or other fruit to bruise or crush them first.

Q: I have been chipping away at a stump in our backyard and would like to know if I can incorporate this wood in my soil or worm bin?

A: Though the individual chips might be too large for a worm bin, you can certainly use the chips as mulch on top of the soil, or incorporate them into your soil. A few chips in the soil are fine by themselves, but if you add a lot of chips all at once, they will steal nitrogen from the soil as they break down. In that case, add some composted manure at the same time to provide extra nitrogen.

If you want to add the chips to compost, treat them as a brown and balance them with greens (lawn clippings, vegetable food scraps, coffee grounds, tea leaves, etc.) Be sure the chips are pretty small (about 1" across). Otherwise they'll take too long to break down.

Q: I am building leaf mold and have a variety of leaf types in bags. Are there any particular leaves that are not good for creating leaf molds?

A: Leaf mold is essentially slow compost made of just leaves. It's used in similar ways to compost, and also for starting seedlings.

Most leaves are fine for creating leaf mold. It's better if you can chop them with a mower or leaf shredder first, but starting with them whole is OK too.

You might want to exclude pine needles or large, waxy leaves like those from magnolias, hollies or rhodies simply because they take too long to break down. If you want to include these types of leaves, definitely chop them first.

Some gardeners are suspicious that leaves from certain tress will harm their compost or leaf mold. I couldn't find any definitive studies to back that up. The primary theory seems to be that, after enough decomposition, any natural poisons are broken down enough not to be a problem.

Here's some more info on making leaf mold: Leaf Mold FAQ at GardenWeb.

Copyright © 2003 Brian Ballard. All rights reserved.

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