[REPOST] How to use your compost

This is a revised and slightly expanded version of an old edition. I’ve never done that before! It’s spring, though, and each time this season comes around - this is the big, burning question on everyone’s mind: how do I actually use my compost?

The answer comes in two parts.

How do I know when my compost is finished?

There’s no test you can run on your compost that will ding a result saying “I’m finished!” There are, however, a set of simple questions you can ask and observations you can make that will give you a near-indisputable reading.

What do you see? 

Your compost should be dark and crumbly, a lot like soil. Put your hand into your pile and sift it through your fingers. If there are still patches of slime or visible and “undigested” food scraps, your compost isn’t ready yet. Let it keep sitting. If you have bulky twigs or wood chips remaining, though, that’s fine. What you really want to avoid is any still-rotting food.

What do you smell? 

Compost that is ready to be used smells like fresh, good earth. This smell is very obvious. Once my friend Vivian came over and stepped onto my back porch, just as I opened up my pile for turning. “What smells so amazing?!?” she screamed. Your compost is ready when it smells good. It should not smell like ammonia or like anything is rotting.

What do you feel?

If the pile is warm to the touch, that means that decomposition is still active and you want to avoid putting actively-decaying compost around your plants. Compost that is ready to use should be cool to the touch.

Once my compost is finished, how do I use it?

There are lots of ways you can put your finished compost to use. You can amend your soil, prepare a garden bed, fertilize mature plants, start seedlings. To be honest, it’s a little hard to mess this part up. Just so long as you are using compost, I think you’re doing great.

Amend your soil - You can use your finished compost to add a burst of healthy microbes and fungi to your soil, which will help it with all kinds of things like water retention, nutrient cycling, and even carbon drawdown. You can do this pretty much anytime you want, and with whatever compost you have available. Just lay the compost down on top of the earth, wet it with a hose or (if you’re water-conscious, which you should be) wait for rain, and let things be. I like to do this in “forgotten” spots around the yard, like crevices between asphalt. Some experts will recommend tilling compost into the soil and you certainly can, but there are tradeoffs to consider. Breaking up the existing earth will disturb networks of mycorrhizal fungi and, perhaps, valuable biological crusts. However, if you’re using your compost on a particularly degraded or highly compacted area, the benefits of tilling and integration will probably outweigh the cons of any potential disruption. Use your best judgement.

Prepare a garden bed - Till one inch of compost to a depth of five inches in your future garden bed. I recommend doing this a few months in advance of planting, in order to give time for the microbes to “settle in.” However, you can get away with as little time as seven days or so. Also, if you don’t know what “one inch” of compost looks like or how to measure five inches… that’s fine. Follow the blanket principle: mix some compost into your garden bed, in advance of actual planting.

Plant something - Throw a pinch or more of finished compost into the hole where you’re about to transplant something.

Dress your vegetables up - Even if you’ve prepared your garden bed in advance with compost, your plants can still benefit from an additional compost-y boost as they grow. You don’t need to use much. Add to the top of the soil in a thin layer, avoiding direct contact with stems. Different plants have different feeding needs, and you may want to adjust how much you use based on what you’re planting.

Perk up a houseplant - Mix a handful of compost into your regularly purchased soil when potting or re-potting a houseplant. I’ve seen it recommended to use one part compost to three parts soil, but I’m generally imprecise and highly unscientific so I just say “a handful.”  

There’s one other thing you can do and this one might be my personal favorite: give your compost away. Not all those who compost also garden. Maybe you live in an apartment without a yard, or have a picky landlord who doesn’t want you to touch the garden. Hey, it happens. I bet you that your local elementary school, community garden, old folks home, or whoever else would love a donation. Your neighbor might like some, your friends might like some—just ask around and see.

There’s also, of course, the option of just never using your compost. You can spend ten years on a pile and never use an inch of it and it’s still better for you and your environment for having done so. :)

Hit me in the comments (or by replying directly to this email!) with the way you plan to use your compost this spring.

Love,

Cass