Marijuana and the weather
Problem: The weather report indicates an upcoming cold spell that could drop below freezing with warmer weather expected by the end of the month. How do I prepare my garden for the cold?
Solution: As defeatist as it might sound, your primary job is to keep the plants alive until the weather takes a turn for the better. At 45*F (7*C) most plants stand a good chance of surviving unscathed. When better weather comes back, the plants will effectively restart the growing process.
If you can bring the plants inside and give them a moderate light-on cycle, then they will be sustained for a while until the weather changes.
Patio heaters can be put in the garden and could ward off frostbite in the plants. You can also construct a temporary greenhouse with a wood frame and plastic coverings that will trap the heat more efficiently and can be taken down with the arrival of better weather.
Polyethylene can be used to wrap individual plants. This will not only protect the plants from wind and rain, it will also preserve some heat. Still, the cold will eventually makes its way to the plants unless you’ve provided them with some source of heat. Forced air heaters might be ideal to heat the plants. Be sure to set the gauge at 70*F (21*C) to avoid overheating.
Problem: The plants are not yet mature, and the weather is getting cooler. How long can the plants stay outside?
Solution: As daylight temperatures descend to the low 60’s (15-18*C), plant growth will start to slow dramatically until it basically stop in the mid-50’s (12-14*C). If you don’t think that the daylight temperature will consistently get above the high 60’s (above 20*C) then you might think about scrapping the crop.
Evening temperatures might be descending into dangerous territory. Indeed, most plants can endure temperatures that drop into the 40’s (5-10*C), but when it drops anywhere below that (under 4*C), tissue damage will be prevalent.
Any solution really relies on the amount of available sunlight. As the Earth shifts seasons from autumn to winter, sunlight intensity and overall longevity will decrease. Plants that might have been in full light in the summer and early autumn are now shaded for most of the day. Clouds might also decrease the quality of the sunlight. In the winter, the plants are not allowed adequate light energy and should be harvested to avoid a wasted crop. Even if the buds are not ripe enough to smoke, they can at least be processed for kief, extracts, or for cooking.
If the weather is cold but the plants are still receiving adequate sunlight, they could be placed behind a clear piece of plastic. This will almost have a greenhouse effect by trapping the sun’s heat and promoting growth in the process.
You could also use items called “passive heaters.” You really just have to fill up some dark-colored containers with water, let them heat up during the day, and then they will radiate heat at night.
Propane-powered patio heaters will also keep the plants warm. They’ll also burn gas that produces CO2 and water vapor. The added CO2 will promote growth.
Problem: The weather is turning humid and moist.
Solution: Start harvesting any and all mature buds. Then, spray the remaining plants with anti-fungals. Try to keep the plants as warm as you can. If humid weather is commonplace while the plants are ripening, you might try different varieties with looser, drier buds.
Problem: Rainy weather is in the forecast. How can the plants be protected?
Solution: Mold abounds in rainy weather because water slips into the buds and creates ideal conditions for molds like Botrytis to thrive. The buds tend to hold and hide the water and humidity in their crevices and it can prove difficult to dry them out.
If you can move the plants or construct an enclosure, then rain will not affect the plants, but moisture still might. Increasing temperatures in the enclosed area (up to the 70’s F or 24-26*C) could protect the plants and help dry out the buds because mold growth would be curbed. Circulating the hot air with a fan certainly helps.
If rain is forecasted as a brief, one-time occurrence followed by a continuation of warm, dry weather, then you can protect the plants by treating them with an anti-fungal like potassium bicarbonate or Serenade prior to the rain. If prolonged rain is expected, then you might just think about harvesting the plants right then instead of having them just turn into mush.
Problem: Wilting appears out of nowhere. One second the plants are beautiful and thriving and then a few minutes later they start wilting.
Solutions: These plants tend to draw up water by maintaining a higher salt concentration within their tissues than in the surrounding soil. In the event that the salts (fertilizer nutrients) become more prevalent in the planting mix than in the plant itself, then that usually suggests that the plant can’t draw up water or it, in fact, just drains from the plant. To fix this, try flushing the soil with pH-adjusted water at 72*F (22*C). The amount of water should be equal to about 1.5 times the volume of the container (e.g. 7 gallons to flush a five-gallon container).
Occasionally, cannabis leaves will droop at the very end of the light period. This is normal and should not cause any worry.
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