Gardentalk – Weed seed eradication and greenhouse materials

In this picture taken in early June 2019, tomatoes, peppers, and other vegetables thrive in the scratch-built geodesic greenhouse that Tom Lafollette made at the Annex Creek Hydroelectric Facility in Taku Inlet. Lafollette explains that he's set up an automated watering and venting system to keep the plants watered and the greenhouse ventilated.
In this picture taken in early June 2019, tomatoes, peppers and other vegetables thrive in the scratch-built geodesic greenhouse that Tom Lafollette made at the Annex Creek Hydroelectric Facility in Taku Inlet. Lafollette explains that he’s set up an automated watering and venting system to keep the plants watered and the greenhouse ventilated. (Photo by Matt Miller/KTOO)

Master Gardener Ed Buyarski answers more listener questions in this week’s edition of Gardentalk.

Kathleen writes: “I have 20 year old soil that has been amended with compost over the years, but grew way too many weeds last year. How do I build it up?”

Buyarski said there are a few different things that Kathleen can do. First, she can cover the old existing garden soil with cardboard and then add new soil and compost on top.

Second option is she can try sifting the soil and picking out the weed seeds by hand.

The third alternative includes covering the garden bed with clear plastic to get the weeds to sprout early. She can then pick out the weeds by hand or torch them with a weed burner before adding a layer of new soil and compost.

But Buyarski cautions against digging too deep through the new soil layer, because that will start germination of the deeper, dormant weed seeds.

Dan writes: “What material do you recommend for a small backyard greenhouse in SE? Glass, polycarbonate, double-wall polyethylene, others?”

Buyarski said it depends on how much money Dan is willing to spend and how much time he is willing to spend looking for salvaged materials.

Recycled, double-pane windows are great for new greenhouse construction.

Polycarbonate is durable and can really help extend a gardening season, but Buyarski said it can be very expensive.

Single-layer plastic over some hoops is a quick way to get started. But it won’t provide as much insulation and extend the season as much as a double-layered, inflatable plastic greenhouse.

Buyarski suggests making any greenhouse as large as you can, so it doesn’t overheat and there is enough ventilation and air movement inside.


Do you have a garden question for Ed? Fill out the form below, and he’ll answer your question in an upcoming segment.

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