A lesson on organic matter – what it is and how to use it

What can you collect in October and put to work to make a better garden? What do folks throw out on the curb that could save them money? What makes yard work easier?

Leaves are the answer. Or more broadly, most organic matter, including pine needles, lawn and landscape clippings, fruit and vegetable leftovers, and any form of compost. You just need to know where to get the O.M. (what soil teachers and books call organic matter) and how to use it.

How odd it is that so many people throw away organic matter in fall, at some cost to the municipality, and then buy a version of the same stuff in spring to enrich and texturize the soil? Depending on your lifestyle, time and strength, here are several ways to get organic materials for free. How to use them follows.

• Leaves are obviously available right now, in the yard and on curbsides. Rake them, pile them, or bag them for immediate or next season’s use. In some places you can just let them lie, as it happens in nature. You may chop them up with the lawnmower (especially the coarse ones such as oak leaves) before collecting them. Many worry about the pesticides or contaminants in other people’s leaves, but if you have doubts, compost them or otherwise age them.

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• Pine needles (or droppings from any conifers) are a great find on curbsides. I have joked about making a bumper sticker – “I brake for pine needles” – but I really do. In fall, I carry large garbage bags, gloves and a rake in the car, and scoop up the lovely material to use in many ways. Do not worry that pine needles will be too acid. The acidifying factor of pine needles is extremely slow, and most soil in this region is too alkaline anyway.

• Food garden remains can be turned under in fall (leafy greens, pea and bean plants) or gathered for compost making. (Do not keep diseased crops around – potatoes and tomatoes for instance).

• Finished flowers including dead annuals and cut-back perennials can be turned into the soil in place or gathered for future use. Plants with seedheads have value for birds and other wildlife if you leave them standing.

• Straw bales are often found on roadsides after Halloween. Accept them from your neighbors. Do not use hay (different from straw) as it is extremely weedy.

• Twigs and branches, depending on size, have many uses. If you suspect serious disease or insect pest infestations, do not gather tree and shrub cuttings. Definitely do not transport wood from other locations if you aren’t familiar with the species and particular health risks.

• Manure from farm animals or your hamster is a rich form of organic matter. If your neighbor raises chickens, accept the surplus. If horses live nearby, figure out what you can acquire and how to use the manure (well aged). Stick with manure from plant-eating animals rather than from carnivores. (Skip the dog and cat litter.)

• Paper and cardboard came from trees and are included in the organic matter category. Shredded office paper, newspaper or cardboard boxes are useful. Avoid shiny box material (cereal boxes, for example) and shiny magazine paper, as these do not decompose readily. There is no danger from using colored newspaper (as used to be the case.)

• Wood chips and sawdust might be free, but read the cautions about how to use them.

• Used potting mix may be depleted for future use in the pot, but still adds texture to your soil.

• Compost is the royal family of organic matter. It is the ultimate soil builder. Learn to make it and use it. In autumn I recommend incorporating unfinished compost into the soil, as you make new piles for next season.

There are so many ways, so find your own methods among these. Experienced gardeners often say that building soil, using organic material, is at least one-third of the activity of gardening.

1. Build a compost pile. All the organic matter mentioned can be used to make compost. How to make one is not covered here, but many sources are available to teach various methods. Check on your municipal ordinances. (Many locations do not allow compost piles with food scraps in them. Piles of leaves and landscape debris are more likely to be acceptable, as they don’t attract rodents.)

2. Turn organic matter under. With a shovel or tiller, turn O.M. into the soil, leaving it coarse and lumpy. Don’t pulverize. Do not turn under woody material such as sawdust or wood chips. They are nitrogen-depleting as they decompose very slowly.

3. Let it lie on top. Spread leaves, straw, manure, potting mix, or unfinished compost over the top of the bare soil of the vegetable, flower, or landscape beds. Chop coarse leaves (oak leaves) with the lawnmower before spreading them. For aesthetic purposes, you might cover messy-looking material with shredded bark or wood chips (in a landscape). To kill future weeds, you could cover the beds with paper, cardboard and heavy black plastic or opaque tarps. A lot of composting goes on under there.

4. Make it a mulch. Pine needles, straw, chopped leaves or compost are fine mulches for retaining soil moisture, blocking weeds and ultimately feeding the soil.

5. Cut and leave them. If you cut the grass and chop the leaves in fall, let them lie and they will decompose and feed the soil. Do not leave thick clumps of leaves or grass however.

6. Bag and store them. If you can’t make a compost pile, or the material you have is very coarse or weedy, you can bag and store it until spring – and then compost or incorporate the O.M. directly. Poke a few holes in the bag to make it less watery and smelly. The bags can also provide insulation against a foundation or planting beds.

The topic is worth a book, so explore further. Depending on what’s available, and your style and energy, there is so much good work to be done to use the organic matter. I hope not to see piles of it on every curbside this month because you are wisely putting it to work. And it is all for free.

Sally Cunningham is a garden writer, lecturer and consultant.

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