Extending Seasons

Marijuana Horticulture

by Jorge Cervantes

Many products protect plants from cold weather and high winds, allowing growers to cultivate earlier and later in the year than would normally be possible.

The earliest and most cost-effective approach to extending the growing season is to locate and take advantage of microclimates such as areas that warm up faster or retain heat longer. Orientation to the sun, wind breaks, and walls made out of materials – bricks, mortar, stone – that will hold the heat and can even prevent freeze-thaw cycles all play a part in evaluating microclimates.

Dark rocks can moderate temperature in a very small area by soaking up the heat of the day then releasing it slowly as the evening temperature cools.

Dark walls and soil will absorb and hold more heat than their light-colored counterparts. Or use plastic mulch which will shade weeds, prevent moisture loss, and raise the temperature of the soil by 5-15F on a sunny day. As plants grow, the leaves will shade plastic and stop the warming effects.

A lake, pond, or small creek will also moderate air temperature, keeping it warmer in winter and cooler in the summer.

Cloches are individual protective coverings that keep plants warm at night. A simple cloche is a milk container with the bottom cut off and the lid removed. Placed over a plant, the plastic will capture and retain heat while allowing ventilation thru the open top. You can make cloches out of wax paper, glass, or jars, or buy them. Commercial units are made of rigid transparent plastic or heavy duty wax paper. They are easy to use and stack well for storage.

The Wall O’ Water is a plant lifesaver. It is a water-filled teepee which uses the heat-emitting properties of water t shield plants from excess heat and keep them warm in the cold. It hold three gallons of water and fits over the plant. During the day, the water absorbs the heat of the sun, moderating the temperature in side the teepee. At night, as the air temperature drops, the water releases its heat, keeping the plant comfortable. The Wall O’ Water does its best work in the spring when there is still a chance of freezing. As water freezes, it releases more heat into the teepee and can protect plants down to 20F.

Covers protect early plants and can help produce a spring crop. The most uncomplicated cover is a sheet or blanket spread over the pant and held down with stones or soil. A low wattage electric light bulb carefully placed under the cover will raise the temperature 10-15F above that f the rest of the garden. Be very careful that the light bulb does not touch any part of the cover, or it may start a fire. Products such as Agronet and Reemay are spun-fiber with sun protection properties that can be used as covers in place of the sheet or blanket.

Row tunnels can be made of clear corrugated fiberglass that is bent into an arch and secured over the garden. Commercial row covers come in many sizes from large enough for dwarf fruit trees to smaller units for pepper plants and rose bushes. Those made with polypropylene will protect plants down to 35F.