Testing Landscape Fabric to Limit Weeds and Capture Heat

This past summer I tried tested black landscape fabric as a weed barrier, and heat retention tool for my pepper plants. The idea being that a) any weeds that germinated in that planter would be starved for light unless they could find a path to one of the holes where the peppers were planted, and b) the black colour of the fabric would serve to capture the sun’s heat, bringing the soil up to a temperature preferred by peppers even on cooler days.

What did I learn?

  • Weed suppression. Well, a single layer of landscape fabric doesn’t seem to starve weeds of light or water. Weeds still germinated and grew under the fabric. In some cases they surfaced through one of the pepper holes, but in many cases they didn’t, yet still appeared to grow well. Despite this, they were restricted to the height they were able to push the fabric, and so didn’t compete with the peppers vertically for sun. Not what I’d expected, but less work than the constant weeding needed with bare soil.
  • Heat capture. Landscape fabric does seem to trap the sun’s heat in the soil. Comparing the temperature of the soil under the fabric to the surface soil of a neighbouring bed showed clearly that this worked.
  • Surprise! There was another learning from this ‘experiment.’ When the pepper plants were the only plants accessible in this particular bed, they were the only plants that avian pests targeted. Crows are smart, and they watch every year as I prepare the soil and plant seedlings. It seems that the black tarp may have brought an appealing focus to the seedlings planted, and almost half of them were uprooted by curious crows over the course of several weeks. Eventually they seem to realize that pepper seedlings represented nothing of interest , but in the meantime halved the number of plants for the 2019 crop.

So, would I do it again? No. At least not the same way. I think next year I may encircle my seedlings with some of the fabric in service of heat capture, but I’m not going to blanket the entire bed. Additionally, I may consider covering the bed with netting or something similar until the plants are off to a good start to prevent the crow disaster from this past year.

 

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