Covering a greenhouse to force twelve hours of darkness lets outdoor growers flower a crop in midsummer and often finish before autumn damp arrives. Automated blackout systems exist, but a tarp pulled by hand works on a small structure. Practical notes on scheduling deprivation runs are gathered at https://breederregularseeds.com, including how heat builds under cover. Skipping a single evening of coverage can reveg the whole crop, which is the risk you accept doing it manually.