How to Tell if your Compost is Lovely or Lethal

    Listen 00:52:57

    Are you yearning to buy a load of bulk compost but suspicious of its contents? Mike McGrath, host of You Bet Your Garden, will reveal two easy tests that’ll tell you if that load is black gold—or the black plague! Plus answers to all your growing questions.

    Questions of the Week:

    “I’ve noticed a lot of leaf curl on my tomatoes and pepper plants this year; the first year I’ve used the free compost that my town makes from all of the yard waste they collect. I’ve read that some lawn herbicides, two that Dow makes in particular, may not be breaking down during the composting process. What do you think? Is there a lab that will test for herbicides?”

    — Zach in Phoenixville, PA

    Tips and tricks for composting »

    • Compost

    Highlights from show for July 11, 2015:

    Pond Chemical Spill

    After a particularly nasty rain, Karen from LaFontaine, IN found that a pond in her backyard had overflowed, sending a bunch of chemical-laden water toward her garden. Karen wants to know how long she’ll have to wait before she can claim her garden is organic again. Mike says that in her case, the organic moniker isn’t as strict as if she was a commercial farmer. He explains that the organic certification only applies to those who sell more than $2500 worth of produce per year, and those individuals who want organic certification for their farm need to refrain from using inorganic chemicals for three years, and that they promote good soil health. Karen grows tomatoes and squashes in a flat earth garden, and she says that they were only underwater overnight, and didn’t die. Mike recommends that she build raised beds, so that if this reoccurs, the plants will be protected from the overflow of the water. He says that, going forward, she shouldn’t touch that soil with bare hands, garden using baseball batting gloves. “If this is gonna happen again and again and again, move your garden to an area of higher ground, and get raised beds so that the water doesn’t get to the soil the plants were growing in.”

    Pear Trees

    Paul from Wildwood Crest, NJ planted four ornamental pear trees. Three of them are doing really great, and the fourth one is doing fine, but not as well. They’ve been in the ground for about ten years, but they were not planted correctly. Mike says that when planting trees, you want a wide hole, not a deep one, so that the root flare isn’t covered, and then fill in around with the soil that’s been removed. The reason not to refill with nice loose soil is that the roots will only stay in the loose soil, never venturing out into the cruel world around them. In Paul’s case, Wildwood has very sandy soil, which works really great when mixed with compost, creating a nice, loose-draining soil. Paul had also put down peat moss, which increases the acidity and does nothing for the structure. Paul also planted Bradford Pears, which are generally a cheap tree which run into many problems and even when planted correctly, they have to be replaced sooner than other varieties of pear. In terms of the one that isn’t doing well, it has been receiving the same treatment as the other three. However, they are mulched with wood mulch, which Mike recommends he get rid of and replace with a compost mulch. “Wood mulch is death to all plants. Replace it with a good two inches of black yard waste compost.”

    Over-mulching Trees

    Diane in Center City, Philadelphia noticed a problem in Rittenhouse Square. All of the trees are horribly overmulched, burying their root flares. Mike says that this isn’t exclusive to Rittenhouse Square, that it’s very common in public spaces all up and down the east coast. Now, there are a couple reasons for it: landscapers are paid more if they use more mulch, and it also works as a somewhat sinister form of planned obsolescence, if the tree dies, the landscaper will be called back to replace it. Mike also mentions a recent visit to a historic site in New Jersey. He is good friends with the landscaping people there, and upon noticing the mulching around those trees, they told him that the landscapers who did the mulching on those trees refused to fix it, and they can’t fire them because it is a state project, and those guys were the lowest bidder. Mike calls for guerrilla action. Organize a group of people together, give them gloves, and remove the mulch yourselves. Don’t count on these landscapers to do anything. “When I retire, that’s all I’m gonna do. I’m gonna drive across America and rescue trees from mulch.”


    Many years ago, Mary from Havertown, PA bought a non-invasive variety of loosestrife. For those who don’t know, purple loosestrife is a beautiful but aggressive plant, pollinated by bees, producing thousands of seeds per plant. Now, many nurseries don’t carry loosestrife for this reason, so Mary wants to know what to do to replace her plants that have died. Mike recommends that she let her remaining plant go, let it pollinate, and then collect the seeds, keep them cool and dry over the winter, and then in Spring, get them started in a loose, light, soil-free mix on top of a heating pad, and see what grows. As for the one that’s still around, don’t give it chemical fertilizers, don’t mess with it, and if it spreads, then she doesn’t have to worry. If it hasn’t, and if it’s achieved a good size, when spring comes, take it out of the ground and separate the roots into new plants. “If you’ve got problems with your car, take it back to the dealer.”

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