Tropical Gardening Helpline: Make your own soil by composting

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The larvae of the soldier fly are voracious eaters of waste matter and will quickly do composting for you in a properly designed bin. (Diana Duff/Special to West Hawaii Today)
Separating worms from vermicompost is easily done by mounding up soil from your worm bin and letting the worms go to the bottom. (Chris Pascual/Special to West Hawaii Today)
Composting garden and kitchen waste is a great way to make your own soil. (Diana Duff/Special to West Hawaii Today)
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Michelle asks: I want to plant a garden but the ground on my property is mostly rock. What do you advise gardeners do, soil-wise?

Tropical Gardener answer: With soil in short supply here in Kona, starting a garden can be a challenge. Of course, you can buy soil at one of several local establishments that carry planting mixes in bulk, but you can also make your own. A relatively easy way to create your own soil, save money and help reduce waste is to compost.

Composting can refer to any system you use that turns kitchen and/or garden waste into healthy soil. The traditional system is centuries old. It relies on creating a pile of organic waste material and letting it passively rot. The rotting process is hastened by naturally occurring microbial activity which converts the waste into nutrient rich soil.

Backyard composters often use a more precise approach. By generating a proper balance of carbon, nitrogen, air and water, the process is faster and the results are more predictable. By occasionally turning (and aerating) the pile you can actually create a fully composted, rich soil in a few months. Our year-round warm weather helps speed the process.

If you are short on time or adverse to turning piles, composting help is available by using some waste-loving critters. Several species of worms are great at composting and some farmers are now using soldier fly larvae to do the heavy lifting.

Worm composting is pretty simple and doesn’t involve anything harder than collecting your kitchen waste and delivering it to your worm bin. Dark, damp and dinner are the three Ds of worm composting. Worms do best in a box or bin that is in a cool spot out of the sun that stays moist (but not wet) and is regularly fed kitchen waste. Separating the worms from the finished compost is the last task in the process. The result of this system is a wonderfully rich vermicompost that can be mixed with native soil or used alone as a highly nutritious growing medium.

Leona Kassel and her husband Chris Pascual have been worm composting for many years. They credit their highly productive garden and the healthy food they grow to vermicompost. These two experienced vermicomposters are offering a free class in worm composting at the Kailua-Kona Public Library on the first Saturday of the 2019. This is part of the series of monthly classes coordinated by the Community Seed Library.

At 10 a.m. Saturday, Jan. 5, Leona and Chris will start by outlining the important steps to successful worm composting. They will share the best ways to set up a bin and give information about maintaining a healthy, active bin over time. They will include ways that vermicompost can be used directly in the soil as well as indirectly to make a highly nutritious tea for foliar feeding your plants. If you want to do the rot thing and get lots of help in the process, worm composting might be the perfect solution.

Another composting system that is a little more complicated to set up but yields great results is composting using black soldier fly larvae. A medium sized colony of BSFL larvae can consume about 2 pounds of household food waste daily. These critters are known detritivores, which means they can break down rotting animal matter as well as plant waste. You can add meat scraps to a black soldier fly bin, which is not recommended in either standard or worm composting.

Composting in any way is the right thing to do. Consider the methods available and get started building soil today.

Diana Duff is a plant adviser, educator and consultant living in a dryland forest north of Kailua-Kona.

Gardening Events

Saturday: “Work Day at Amy Greenwell Garden” from 9 a.m. to 12:30 p.m. Meet at the Garden Visitor Center across from the Manago Hotel in Captain Cook. Volunteers will be able to help with garden maintenance and are invited to bring a brown bag lunch. Water and snacks provided. Call Peter at 323-3318 for more information.

Now through Dec. 21: Applications are due for Natural Resources Conservation Service cost share/agricultural assistance programs. Call the Kealakekua office at 339-9042 for more information.

December ongoing: Agricultural Apprenticeships are available throughout the mainland. Applications are being currently reviewed. Go to https://quiviracoalition.org/apprenticeships/ for more information.

Farmer Direct Markets

Wednesday: “Hooulu Farmers Market” 9 a.m. to 2 p.m. at Sheraton Kona Resort &Spa at Keauhou Bay

Saturday: “Keauhou Farmers Market” 8 a.m. to noon at Keauhou Shopping Center

“Kamuela Farmer’s Market” from 7 a.m. to noon at Pukalani Stables

“Waimea Town Market” from 7:30 a.m. to noon at the Parker School in central Waimea

“Waimea Homestead Farmers Market” from 7 a.m. to noon next to Thelma Parker Gym in front of Thelma Parker Library

Sunday: “Pure Kona Green Market” 9 a.m. to 2 p.m. at Amy Greenwell Garden in Captain Cook

“Hamakua Harvest” 9 a.m. to 2 p.m. at Highway 19 and Mamane Street in Honokaa

Plant Advice Lines

Anytime: konamg@ctahr.hawaii.edu

Tuesdays and Thursdays: 9 a.m. to noon at UH-CES in Kainaliu – 322-4893

Mondays and Fridays: 9 a.m. to noon at UH CES at Komohana in Hilo 981-5199 or himga@hawaii.edu