Gardening with Xpress: Composting: the hotter, the better

HOT COMMODITY: Composting works best if it generates heat. Photo courtesy of Wild Abundance

Warm greetings, gardeners. Our famous and beloved Herb Fest has come and gone, and we’re officially past the last frost date. Time to get all those warm-season crops in the ground! Be sure to send in your questions to as your crops get growing. 

Weed season

Is it OK to compost weeds? I’m thinking of dandelions in particular. If one were to do so, wouldn’t it potentially generate more dandelions within the compost? 

The short answer is yes, it’s OK to compost weeds. But unless you manage your compost pile so that it gets really hot, the seeds of those weeds may survive. If you spread compost that contains viable weed seeds, they likely will sprout. This is a great way to spread weeds around. However, if they are concentrated in one area, you can usually do them in easily with a stirrup hoe or another quick technique when they are but wee seedlings.

Have you ever noticed steam rising up from the giant mountains of mulch at the Stump Dump by the river? Or even from a leaf pile in your yard? This heat is the result of microscopic organisms like fungi, bacteria and others consuming organic matter and turning it into energy as they go. You can build compost piles to maximize this microbial activity and the heat it generates. This process also breaks down weed seeds and many pathogenic organisms that would otherwise be dangerous to people or plants, and it makes for a finished compost that’s rich in humic acid and other substances that help garden veggies grow well.

To get compost to really heat up, you’ll need to build a large pile with a balance of “greens” (nitrogen-rich materials like fresh weeds and grass clippings, food scraps, etc.) and “browns” (carbon-rich materials like straw, dry leaves, small twigs, or even paper and cardboard). These materials will need to be sufficiently moist, but not soggy, and you’ll need to turn the pile every several days to add oxygen so that the microbes that create the weed-seed-destroying heat can breathe and really get going. If you don’t manage a compost pile like this, it is unlikely that it will get hot enough to kill weed seeds.

Making hot compost is a bit labor intensive, and you’ll need to have a lot of materials on hand all at once. The minimum-sized mound for this method is 4 feet by 4 feet by 4 feet and bigger is better. An ideal ratio of greens to browns is between 1-to-1 and 1-to-3. Most of us simply layer kitchen and garden scraps with straw or dry leaves as these organic wastes are produced. This is a more passive approach and is a wonderful way of keeping organic material out of the landfill. However, it does not generate the kind of heat that will kill weeds or weed seeds.

Winter rye

I’ve grown winter rye as a cover crop. It’s very lush and thick, and I’m ready to plant vegetables where it’s growing. What exactly do I do to make the switch?

Cover crops are one of the best ways to build and protect healthy soil, feed soil organisms and above-ground pollinators, grow mulch material, and care for garden beds in between vegetable plantings. But cover cropping can feel complicated and intimidating, too.

One of the biggest challenges, especially with winter rye, is just what you’re asking about: how to transition from the cover crop to vegetables. Here are the steps that work well for us that also can be applied to other kinds of cover crops. 

First, pay attention to the life cycle of your cover crop and “terminate” (yes, that’s the official term) during flowering. This will be more effective at actually killing the plants, rather than just giving them a haircut that they will regrow from, and it will mean that the highest level of nutrients will be present in both the roots and aboveground parts of the plants.

CROP COVER: Rye is a great way to feed the soil in the winter. Photo courtesy of Johnny’s Selected Seeds

To terminate a cover crop, you can either mow or crimp. For mowing, I like to use a hand sickle (the Japanese kama is my favorite) or a scythe. A weed whacker will do but will make more of a mess. Another option is to crimp by laying a heavy metal T-post down on the cover crop and standing on it. This is easiest with two people; you’ll repeat the crimping motion every foot or two until the whole area is squished to the ground and crushed at the base. 

If you mow, you’ve got the option of removing all that plant material and using it for compost or mulch elsewhere. If you crimp, it will lay as mulch in that area. If you plan to till, mowing is a better option so that you’re not trying to till through a bunch of plant material lying on the ground. In the case of tilling, you’ll mix in the remaining stubble and roots, along with any amendments you’re adding, then be ready to plant. 

If you opt against tilling, you can smother the bed with cardboard, woven polyethylene weed fabric, or another opaque material and wait for it to completely decompose before planting. Or if the plant material you’ve mown or crimped is sufficient to make a thick layer, you can simply transplant into the stubble. The mulch layer should inhibit regrowth if the timing was right. Another option is to spread a 1- to 3-inch layer of compost or topsoil on top of the terminated cover crop and plant directly into this.  

All of these approaches will allow the nutrients from the cover crop to nourish the soil; both the roots and aboveground parts (remember, plants’ bodies are half or more underground) will decompose and feed soil organisms and the vegetables you plant.

What’s what

What is the difference between an annual and a perennial?

Different plants live for different amounts of time, and it takes different plants varying lengths of time to mature and produce seed. Enter the terms annual, biennial and perennial.

Annual plants grow from a seed, mature, produce their own seed, and die, all within the cycle of one year. Many familiar garden vegetables are annuals — for example, tomatoes, zucchinis, cucumbers, green beans, peppers, okra, lettuce, spinach, etc.

 Biennial plants take two years to complete their life cycle. In general, they grow vegetatively during the first year (just leaves and stems, no flowers). Then, in their second year of life, they grow flowers that eventually ripen into seeds. Some examples of common biennial vegetables are carrots, beets, onions and celery.

Perennials live for more than two years; in many cases, much more than two years. Ancient redwood trees are perennials, as are wild and cultivated berry bushes, all fruit trees and many garden herbs like sage, rosemary and thyme (not parsley; it’s a biennial). In our climate, some perennials are cultivated as if they’re annuals. We replant these each year because freezing winter temperatures kill them, but we like having them around. In warmer climates, there would be no need to replant. Perennial vegetables are a lesser-known group of perennials that are fun to add to your garden. Check out my blog post about 10 perennial vegetables you’ll love here:


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