The Rapid Composting Method

Plus, Poinsettia Purchasing Pointers

Dec 17, 2021

On Episode 157 of the Garden Basics Podcast (released Dec. 17, 2021), college horticulture professor (in a former life), Debbie Flower and I tackled a question from a listener in St. Louis wondering what to do with all those leftover garden scraps from dying vegetables, herbs and flowers. In order to improve the soil below, he wanted to leave those cut up pieces on top of the garden bed. Unfortunately, he would be better off composting that debris, in order to kill off any remaining insect eggs or disease spores. The finished compost, the saying goes, is “gardener’s gold”.

A couple of keys to a successful compost pile, explained Debbie Flower (aptly named, no?), is to make sure it is a hot compost pile (140 degrees is ideal); and, the way to keep it churning along at that temperature is to add oxygen, but let someone else do that job:

“A hot compost pile will kill any diseases or insects or eggs or undesirable things that are on the plants,” says Debbie in Episode 157. “There's life in that pile to make it hot. There are microorganisms - algae, fungi, bacteria - that are living off of the chipped wood, and they are biological organisms, and they create heat just like a human body does. As they're active, they give off heat and that helps them live and it helps other things move in and it helps their presence. And their heat helps to kill the bad things in a compost pile. They need both carbon and nitrogen to survive. And so it is nitrogen breaking down and it's carbon breaking down, but it's through the process of these live organisms.”

A compost thermometer inside a two-day old, dumped pile of chipped/shredded eucalyptus trees (future mulch). Outside temperature that day? 50 degrees.

Debbie makes a very good point about the carbon-nitrogen ratio, and how important that is to a hot compost pile. If you see instructions for building a compost pile, they'll always tell you to alternate a layer of “brown” with a layer of “green”. The “brown” being carbon (woody material), “green” being any sort of green matter - leaves and green stems - that's your nitrogen. P.S. regarding that pile of future eucalyptus mulch: eucalyptus is OK to use as mulch, really. Read about it here.

Debbie continues:

“I worked at one time for the Sacramento city school district, at a vocational high school for adults. And we maintained the landscape as part of the horticulture training. And we had a little chipper. People had to work long and hard to get the stuff broken down. But we didn't pay attention to the ratio of carbon and nitrogen. We just took whatever we had and chipped it and threw it in the pile. We had a concrete pad up against a brick building. So we threw it in a pile up against this building every day. Every day, five days a week. The students took the pile and moved it from one place to another. The next day, the same thing, they turned it back. The next day turned it back again. We had compost in two weeks. The number one limiting factor in a compost pile is oxygen, to keep those microorganisms alive. People think it's water. Yes, it has to be moist; but moist, not wet. You might think it might need nitrogen. You need nitrogen, but not a lot of it. There was a organization in Tucson, Arizona that was studying composting, and they came up with the same answer, oxygen. That's the number one. Tucson Arizona is a very hot, very dry place. And they watered the compost pile and they added the right or the wrong carbon to nitrogen ratio. But the number one limiting factor in the compost pile was oxygen. But as the components of the compost pile break down as you turn it, they get smaller and smaller and smaller. So the spaces between particles get smaller and smaller and smaller as they nestle closer and closer together. And by turning it some more, you open up those spaces and you allow more oxygen into the pile, which allows the micro organisms to work faster and allows that carbon and nitrogen to break down faster. And so, when we get the finished compost out, we have lots of great organic matter.”

If you don’t have a small army of able-bodied landscapers handy, the University of California-Berkeley Professor of Plant Pathology, Robert Raabe, developed the “Rapid Composting Method”, which produces finished compost in a very respectable three weeks. The secret to his success: three, side-by side bins, each three feet long, wide and high.

3 bin composter. Each bin is 3 feet long, wide and high.

Here’s a brief synopsis of his instructions for constructing the rapid composting system:

1. Material will compost best if it is between 1/2 to 1-1/2 inches in size.

2. For the composting process to work most effectively, material to be composted should have a carbon to nitrogen ratio of 30 to 1.

3. Composting works best if the moisture content of materials in the pile is about 50 percent.

4. Heat, which is very important in rapid composting, is supplied by the respiration of the microorganisms as they break down the organic materials. To prevent heat loss and to build up the amount of heat necessary, a minimum volume of material is essential: a pile at least 36" x 36" x 36" is recommended. If less than 32", the rapid process will not occur. Heat retention is better in bins than in open piles, so rapid composting is more effective if bins are used.

5. The compost pile needs to be turned to prevent the pile from getting too hot. If it gets much above 160 F, the microorganisms will be killed, the pile will cool, and the whole process will have to start from the beginning. By turning the pile it will not overheat, and it will be aerated also, both of which are necessary to keep the most active decomposers functioning.

6. Once a pile is started, do not add anything (with perhaps one exception, which will be mentioned in 9). The reason is that it takes a certain length of time for the material to break down and anything added has to start at the beginning, thus lengthening the decomposition time for the whole pile.

7. Nothing needs to be added to the organic materials to make them decompose.

8. If done correctly, a pile will heat to high temperatures within 24 to 48 hours. If it doesn't, the pile is too wet or too dry or there is not enough green material (or nitrogen) present. If too wet, the material should be spread out to dry. If too dry, add moisture.

9. If the C/N ratio is less than 30/1, the organic matter will decompose very rapidly but there will be a loss of nitrogen. This will be given off as ammonia and if this odor is present in or around a composting pile, it means that valuable nitrogen is being lost in the air. This can be counteracted by the addition of some sawdust to that part of the pile where there is an ammonia odor - sawdust is very high in carbon and low in nitrogen (a high C/N ratio) and therefore will counteract the excess nitrogen.

10. Materials which should not be added to a composting pile include soil, ashes from a stove or fireplace, and manure from carnivorous (meat-eating) animals.

11. The rapid decomposition can be detected by a pleasant odor, by the heat produced (this is even visible in the form of water vapor given off during the turning of the pile), by the growth of white fungi on the decomposing organic material, by a reduction of volume, and by the change in color of the materials to dark brown. As composting nears completion the temperature drops and, finally, little or no heat is produced. The compost is then ready to use.

Here’s the link to all the info about the Rapid Composting Method.

The benefits of rapid composting, according to Raabe:

• The production of a valuable soil amendment from many organic materials which normally might be wasted.

• Compost can be made ready for use in as short a time as 14 to 21 days.

• Rapid composting kills all plant disease producing organisms if done as described. It does not inactivate heat resistant viruses such as tobacco mosaic virus.

• Insects do not survive the composting process. Though some may be attracted to the pile, if they lay their eggs in the compost the will destroy them.

• Most weeds and weed seeds are killed. Some weeds such as oxalis bulbs, seeds of burr clover, some amaranthus seeds and seeds of cheese weed (Malva) are not killed by the high temperatures in the pile.

Here are instructions on building your own three-bin system from Pierce County, Washington’s Department of Public Works.

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It’s Poinsettia Season! How to Keep this Tropical Plant from Getting Stressed Out This Winter.

Sure signs that December is upon us: Bob Dylan's "Christmas Island" is heard between announcements for deli tray bargains in the supermarket; Christmas tree lots pop up, seemingly overnight, on bare street corners; and everywhere you shop, rows and rows of that brilliant red holiday plant, the poinsettia, fill the front area of the stores.

Among the varieties available are poinsettias that expand your color choices, beyond basic red. New colors include peach, salmon, coral, white, rose, pink and variegated combinations of those shades.

Here's what to look for when hunting for a healthy poinsettia:

• Avoid purchasing poinsettias from outdoor displays. Temperatures below 50 degrees can rapidly shorten a poinsettia's life.

Just say “no” to poinsettias on display outdoors when temperatures are below 50. They ain’t livin’ long like this.

• Choose poinsettias with fully mature, thoroughly colored bracts. The bracts are the red, pink, yellow or speckled modified leaves that catch your eye from a distance. Avoid plants with too much green around the bract edges.

• The true flowers of a poinsettia are the small yellow berries (also called the cyathia) in the center of the bracts. Make sure that the smaller bracts surrounding these berries are fully colored. If these secondary bracts aren't fully colored, the plants will quickly fade and lose color.

• Examine the plant's soil. It's best to avoid waterlogged soil, particularly if the plant appears wilted. Such a condition could signify irreversible root rot.

• Choose poinsettias with lush green foliage that is undamaged and free of discoloration. The foliage should be plentiful all the way down to the soil line, an indication of an active, healthy root system.

• Re-inserting the poinsettia into a large, roomy shopping bag will usually provide adequate protection for transporting the plant when it's cold and windy.

The experienced shopper can find much more variety in poinsettias at the nursery or flower shops instead of grocery stores. "The poinsettia is a very versatile plant," says Paul Ecke Jr. of the Paul Ecke ranch, a San Diego area-based business that is regarded as the world's premiere poinsettia growing facility. "We can grow a poinsettia in a two inch pot, suitable for an office desktop, all the way to a poinsettia topiary tree several feet tall. In between we have hanging baskets of poinsettias, as well."

And there are now many more varieties beyond the familiar red-colored poinsettia, including pink, yellow, variegated and purple.

"The 'Plum Pudding' is the first and only purple poinsettia," says Ecke, whose growing grounds produce over a half million plants for sale each year. "It's a wonderful decorator color that fits into Victorian as well as contemporary color schemes."

No matter the variety, a little care can help a poinsettia last well through the holidays. That care starts at the retailer. "It really gets my goat when I see plants not getting watered in the stores," says Ecke. "You want to buy poinsettias from a store that is taking care of them, which includes watering them and not displaying them outdoors." He advises choosing poinsettias that have medium to dark green foliage that extends to the bottom of the pot. Steer clear of poinsettias with naked branches or yellowing leaves.

"The best way to determine if a poinsettia is still fresh is to examine the flower," says the U.C. Cooperative Extension Master Gardener Lori Ann Asmus. "However, the very bright, colorful part of the plant, which is usually red, pink or speckled, is not the flower. Those are modified leaves. The poinsettia flowers are the little, yellow bead-like parts between those modified leaves. If that yellow flower looks tight and waxy, you can be sure it's a young poinsettia plant, which will last a lot longer. If that flower, though, looks brown, bypass it; that poinsettia is past its prime. And if there is no yellow at all, move on. That plant is very old."

A native of Mexican jungles, the poinsettia will sulk if allowed to endure temperatures below 50 degrees or not get regular waterings. In the house, the best area for the poinsettia is where it can get plenty of light, out of the way of any drafts or heating vents. A southern facing window is ideal. "And there's no need to worry about displaying poinsettias around children or pets," says Ecke. "Poinsettias are not poisonous; but don't eat them."

And if you are inclined to nurse that poinsettia through the spring, summer and fall:

• If you haven't done so already, remove any foil wrap around the poinsettia's pot to allow for drainage, putting a plate or saucer beneath to catch any excess water.

• Poinsettias do like water; but need excellent drainage. Be sure to drain off any standing water from the saucer.

• Although the plant may look great sitting on your dining room table, the poinsettia will thrive where it can get plenty of light, out of the way of any drafts or heating vents. A southern facing window would be ideal.

• In late March or early April, cut back the plant so that two buds remain, about six inches from the base. The plant may still look elegant before you start this radical surgery, but the pruning is necessary to help it look great for next December.

• In April, place the plant - pot and all- outside in a sunny, warm area; against a south wall beneath the overhang of your house or apartment would be ideal. Keep the poinsettia watered, pruning back the branches by a couple of inches in June and August to keep the plant from getting leggy. When the red color begins to show, start feeding the plant with a fertilizer that has a bit more nitrogen in it than phosphorus and potassium.

• In October, before the first frost, bring the plant back into the house and keep it in a dark closet or room for at least fourteen hours a day. The plant will bloom only when it has had these long "nights". And by next Christmas, you'll again be able to enjoy the striking beauty of that same poinsettia plant. Maybe.

If all this sounds like a lot of work, it is. And the end result may not be as spectacular as the original plant's bloom. The good news: there will always be more colorful poinsettias for sale next holiday season.

Beyond The Garden Basics with Farmer Fred

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