5 Reasons to Start Garden Composting in Planter Boxes

Don’t Clean Out Your Garden Boxes or Planting Containers. Add In!

5 Reasons to Start Garden Composting in Planter Boxes

Fall means yard cleanup. Organic debris becomes garden compost. But small spaces might not have room for composters or piles. Garden composting directly within planter boxes solves this issue.

We started garden composting within our planter boxes out of necessity. Our 1/8th acre means every square foot is precious. We started growing lettuce in containers when I needed fertile ground for long-rooted plants like indeterminate tomatoes. Chard, mustard greens…anything small found homes within planter boxes placed on the driveway. But after a couple years, we noticed the soil was dry and pale, the plants faring progressively worse. We needed more organic material within the containers.

We’re also busy people. And sometimes, at the end of a tedious day, I don’t remember to go outside and stir the compost. We needed a simpler way to use our resources and leave soil ready to grow more food next year.

During the coldest months, we bring meat rabbits inside to give birth. Mom and babies live within our coolest room until the little ones have fur, then we acclimate them back outside during warm days. But indoor livestock means indoor manure. We just run to the driveway and dump dirty bedding into the planter boxes. Through rain and snow, freezing and thawing, the manure breaks down. Nutrients leach into the soil. And in the spring, we stir the boxes and plant. No additional composting is necessary.

Those planters grow bushels of eggplant or peppers within eight inches of dirt. All because the soil is so improved.

Garden composting within planter boxes combines yard cleanup, kitchen waste, and an existing planting system to make full use of your resources. With very little work.

Photo by Shelley DeDauw

Garden Composting Within Containers: The Reasons Why

Replace Nutrients for Next Year: It’s simple science. Though enzymes and amino acids are manufactured naturally, elements such as iron and nitrogen cannot be created or destroyed. So, if this year’s tomatoes drew up all the magnesium and calcium that prevent blossom end rot, your nightshades may have a problem next year. Chemical fertilizers add in certain elements, such as nitrogen and potassium, but most don’t provide all the micronutrients necessary for full and proper plant development. Continually adding organic material keeps these elements available.

Feed Microorganisms: Healthy soil contains life; even container gardens contain fungi and bacteria. Microorganisms and plants both feed off nitrogen, and certain microbes access the nitrogen first. Plants can miss out. Organic material gives fungi and bacteria something to consume, which breaks the material into nutrient forms accessible by both microbes and plants. When those microbes die, nitrogen within their cells becomes available for plant growth. It’s this cycle of microbial life which supports organic gardening.

I attended an Agricultural Extension class where the presenter said, of all organic material you add this year, 50% will be available for plant use next year and 2% the year after that. The University of Minnesota makes a similar claim in a program called Tillage: only 10-20% of original organic material becomes part of the soil’s organic matter. A lot of the rest converts to carbon dioxide over a few years.

So adding new organic material each year provides food for these microbes which, in turn, make the right nutrients available to plants.

Enhance Crop Rotation: Planting tomatoes in the same spot year after year, without improving soil, will mean poor tomatoes in a few years.

Different plants use different nutrients, so rotating crops allows those nutrients to rebuild. Planting a light-feeding crop, such as leafy greens, gives soil a couple years to build back up so it’s ready when you plant another heavy feeder. Add organic material in the fall then plant something from a different family than whatever you had in the planter this year.

Some plants actually improve soil. Legumes, such as peas and beans, have root nodules which fix nitrogen. Some of that nitrogen is available that same year, but most is available the next year, as roots decay. Growing peas or beans in containers, and leaving roots intact all winter, helps get the soil ready for heavy feeders the next year.

Garden Composting

Save Time and Labor: Combine fall cleanup with garden composting. All science aside, this is my favorite reason to compost in containers. The garden and soil are as tired at the end of the season as I am. I love being able to rake up leaves, or clean out rabbit hutches, and dump debris directly where I need it. And I don’t even have to dig it in. Mulch isn’t unattractive within planters, so I’ll toss in my kitchen waste, cover that with manure, then top it all with leaves or dry grass. And I’ll leave it that way all winter, only stirring it in the spring before planting. Freezing breaks down cellular structure, leaving organic material soft and ready for microbes to move in and make nutrients available while plants grow.

Save Space: Tumbling composters cost money and, honestly, I make enough waste to justify purchasing six of those contraptions. Garden composting within separate piles can be challenging when dogs and turkeys roam my yard. So I restrict my composting to containers or within the ground itself.

Fall is the perfect time for this type of garden composting because the frost has moved in and killed the sensitive plants. Canning season produces peels and cores. And don’t forget all the “browns” of garden composting, the leaves and straw. This year I followed straw bale gardening instructions for the first time, leaving me with ragged and spent bales after I harvested the sweet potatoes. I’ve dismantled those bales and used them for garlic mulch or a “brown” to keep soil loose and aerated.

If I’m building a new planter box, I’ll wait until spring to purchase garden soil. I call this system the Three Year Planter Box, and it’s my way of slowly extending my homestead by using available materials. All winter, I run outside just long enough to dump the compost bowl into a new planter. In goes straw, rabbit manure, dryer lint, spoiled livestock feed, coffee grounds, and the leaves that blow into my yard. In the spring, I purchase enough soil to top the material by three inches and I’ll plant short-rooted crops like leafy greens, enjoying rapid growth from active decomposition within the planter.

Photo by Shelley DeDauw

Garden Composting Within Containers: The Dos and Don’ts

Don’t let diseased plants remain. Either burn them or discard in a manner that gets them off your property. This includes plants infested with insects such as squash bugs. Ashes from these plants may be added back in, to raise the pH of acidic soils.

Don’t use fresh chicken manure. After winter, manure will no longer be “fresh” and won’t burn plants. But garden boxes use cold composting, which doesn’t kill microbes. Using composted chicken manure ensures harmful bacteria are dead before they enter your soil.

Don’t use manure from the three Ps. People, pigs, and pets. Waste from humans or omnivorous animals contains way too many bacteria.

Don’t add bones, oils, or unnatural products such as plastics. They don’t break down the right way, if at all. If you use bone, purchase bonemeal.

Use a good mix of greens and browns. Greens provide a lot of nitrogen; browns provide too little. Keeping the math right takes energy you may not have. Just remember to use a mix. Greens include manure, compost, kitchen waste, clover, and alfalfa. Browns are leaves, dry grass, hay and straw, and any wood products. If you use sawdust for animal bedding, add it to gardens with a conservative hand. Too much can bind up nitrogen for over a year.

Find Rabbit Manure. I’ve never added so much rabbit manure I couldn’t grow crops. As long as it’s mixed in and I have 25% soil to 75% manure, seeds sprout and flourish. Young crops don’t burn. Watering breaks down pelletized manure like slow-release fertilizer, and soon it becomes part of the soil. Rabbits are obligatory herbivores, which means they don’t eat certain foods which promote the growth of harmful bacteria. Domestic rabbits also rarely have diseases such as tularemia.

Carrot seedlings, growing happily in rabbit manure.

Leave healthy roots in place. If your plants have not become diseased, don’t worry about pulling them out. Let the roots decay over the winter, especially those of legumes. Just cut plants off at the base if you must remove them. In the spring, loosen soil and pull out any tenacious plant material which may interfere with this year’s crops. You’ll probably find that most roots have broken down and aren’t a problem.

Let yourself be lazy. Unless you’re worried about animals or the appearance of compostable waste, just dump it in. Collapse old, spent plants back into the container and layer manure on top. And if you are worried, bury fresh waste beneath soil.

Long, cold winter? Solarize! If temperatures stay too low, bacteria won’t thrive. Colder zones such as five and lower may benefit from laying clear or black plastic atop planters after adding organic material. This keeps boxes warmer and encourages decomposition. Be sure materials inside are moist.

Garden composting within containers is a valuable space-saving skill which also maintains the health of soil, crops, and the family relying on the garden. Remember which materials to add, which to throw away, then relax. Let the seasons do their work.

What garden composting method do you use? Have you composted within planters? Let us know in the comments.

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