I’ve researched the difference between transparent and opaque greenhouse coverings on the web and wondering if you agree for my application the transparent covering is better? Here’s what I have read:
Opaque: mature plants, diffuses and provides more even light, less heat buildup.
Transparent: seedlings, more direct light, i.e. 90% of sunlight found outdoors, hotter so requires more venting, more heat when it gets cooler outdoors. More leggy – not sure what they mean by this as they would still get light from top and sides.
What I want to do is a hoop house, over 4 vinifera grape vines growing in the ground, from spring to late October to protect vines and fruit from rain and dew, decreasing the need to apply fungicides, increasing the heat units particularly in the spring and the fall to better ripen the grapes. I’m thinking the plants should get as much light as possible as if they were growing outdoors so why not clear plastic? Heat buildup would mean opening the two doors at each end of the greenhouse – size 6ft wide by 12 feet long.
Know of one winery doing this but not sure how clear or opaque and if using the best material.
Robert in Ottawa
Indeed, most hoop tunnels are transparent and vented as you describe. Note that your tunnel will have to be tall since you will still have to trellis your vines. You will find an interesting description of grapes, rooted in the ground, but growing in a greenhouse environment in the Royal Horticultural Society guide here. Throughout Great Britain and Ireland, this method of growing grapes is common practice.
The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) has a general guide to growing wine grapes in northern climates, which has a section on cold maintenance practices you may find helpful. You can find it here.