The Simplest Way to Extend Your Growing Season: Create a Micro-Climate.
Have you ever noticed how much bigger and greener the grass is around the base of a tree? That's because it's growing in a "micro-climate". Or, a modification of the natural elements like a warm, sheltered, sloping, and heat absorbing dark colored background and dark soil spot that is obviously warmer than the center of your yard. You can create one by finding the south facing side of an outbuilding, putting black plastic or tar paper behind the structure, mounding up dark, rich, black composted soil at a 40 degree angle and protecting with a barrier from the windward side. I use a standard weed barrier, like black woven poly stretched between two bamboo canes which were stitched in the ends and then pounded in the soil. That is to say, I cut about 6 feet of weed mat and then cut little slits every foot on the ends and weaved the bamboo in and out of the slits to secure the cloth to the bamboo. This will give you 30% increase in soil temperature compared to the surrounding environment. Do you have any old windows lying around? They can also be used as a temporary cold frame. Just lean them up against the building and then lean one on each end or at least the windward side.
Do you have a lot of rocks on your property? Rocks are great soil warmers. They absorb heat and light all day and then slowly release them back to the soil at night. Try making a raised rock wall bed somewhere against the south side of a building. Fill it with dark, black rich composted soil again and add your wind break.
Your job is to find, improve, or create nice micro-climates for your blocks to be happy!
Try Cloches (pronounced cloash), French for Glass Bell Jars:
French intensive market gardeners of the sixteenth century were called Maraichers (pronounced Ma-ray-shares), named after the swampland (marais) they were forced to move to, due to the high cost of city land in Paris. They too, had to drain off this swamp land to farm it. They were the originators of season extension using glass. They also developed an excellent system of interplanting and succession planting for a continual harvest in small spaces. They used an appliance called the cloche, a bell shaped glass jar, about 16" tall and 18" in diameter. The Maraichers placed the cloches over newly transplanted seedlings like lettuce, spinach, leafy greens, herbs, or young cucumbers. This is a great example of creating a micro climate. You can purchase cloches made out of durable UV resistant plastic, as glass is too heavy and would break easily. This is an inexpensive way to transplant a few plants before the last frost date.
Floating Row Covers:
The next step up would be to provide a blanket for your garden rows to protect from frosts and cold windy day. This idea of a blanket is known as the Floating Row Cover. FRC's are spun bound polypropylene that come in all widths and lengths and are self ventilating. They also have different weights, so the lightweight blankets can be placed directly over the plants but still not get blown away. It is water and air permeable, so there is no need to remove it until the "coast is clear", just let the rain water your plants through the blanket. It can be left on even further to protect crops from insect damage, wind damage, and extreme temperature damage like heat and freezing. It conserves soil moisture and deters birds and animals. Floating Row Covers and Blankets can also protect trees from frost damage, giving us northerners a chance to grow almonds, citrus and avocados.
True to their name, they can float right on top of plants, but what about a structure with flexibility? That is known as the Low Cover or Tunnel. Using a heavier grade of spun bound polypropylene, and some #9 wire(found easily at home centers), you can make little hoops and place over your row crops every 2-4 feet. Depending on your wind or snow loads, the closer together the wire hoops are, the stronger the tunnel is. You then cover with the blanket and lay some sod or dirt on the edges to keep it weighted down over the hoops. Bunch up the ends in a tennis ball or something round, wrap a rubber band around it and use another piece of wire to make a "fabric staple", and staple the blanket end with the bunched up ball to the ground. You can make these tunnels as long as you like, but the accepted width of a wire hoop, before it looses it's rigidity would be about 6 feet, using a foot on each side to be buried or poked into the ground.
Floating Row Covers can easily be made from #9 gauge wire found at a hardware store cut into 6-8 foot lengths. Jab into the ground and bend about 3-4 feet apart. Cover with the Floating Row Cover and then secure down with dirt clods. Its easy!
Slitted Row Covers:
Another variation of the self ventilating row covers is the slitted row cover. Although, not as frost hardy as the blankets, the slitted row covers can be placed over hoops in rows and simply left there all year. The benefits are in the clear plastic, versus the less light translucence of the spun bound blanket.
Slitted Row Covers have little slits on two sides for ventilation. Not completely protected from freezes, your plants will still enjoy about a 5 degree protection from frosts. They will take some labor to get in and out through the season as you water, cultivate, and harvest. And, they do not last very long, as the plastic is thin and not as UV protected as the blankets. Slitted row covers are best used for melons where they can be transplanted earlier with the soil blocks and left in hot bed all year 'till harvest. Bury some drip tape or lay out some drip irrigation for each plant. Leave the ends open for pollinating insects. Top dress with horse manure for heat and CO2, or use black or green plastic mulch. This will speed up harvest by 6 weeks! Definitely worth the extra expense for the northern crowd to get ripe melons in the summer! But, yes, lots of plastic being used and hopefully recycled, right?
Our Farm's Favorite: TUFBELL now called Dio Betalon
As I have mentioned before, I try to use the least amount of plastic as possible. To that end, I need something that will last for years, tougher than plastic, easy to use and still recyclable in the end(but my Tufbell is in it's 6th season!).
Tufbell is a floating row cover that is made from a high-tech polyvinyl alcohol (PVA). It is unique in it's way it absorbs water during the day, letting it pass through to the plants, but at night, the water freezes to the fibers and forms a tight freeze-proof(up to 10 degrees) barrier, like an igloo. It is breathable, and won't get over 90 degrees in the heat of summer. It allows 95% light transmittance! It is reinforced with nylon threads every square foot. Additionally reinforced again with wide bands every 39", which allows it to be sewn together to make huge pieces. We have sewn them together to make an inner lining for greenhouses and could grow crops year 'round in unheated structures! Sew with nylon thread to make larger pieces. It is easily washed and easily repaired, anti-static, UV stable, and is the unquestionable longest lasting row cover in the world. It can float as a blanket or you can make little tunnels. We have made large walk in tunnels for tomato production. Simply unprecedented and durable.
Second best choice: 4 year, 6 mil, UV resistant clear Agriculture Plastic over wire and buried in soil.
This is called "Chenille" in French, and it means caterpillar. This is stretched out over #9 galvanized wire hoops 7 feet long with a small loop twisted in them at 12 inches from the bottom of each end, and is cut from a roll found at most hardware stores. Space the hoops every 3 feet. Then, use old bailing twine to go through the hoop loops every other hoop. Close the ends with U shaped wire from the same roll to make U stakes.
Hoop Loops: Run the twine through opposite loops across the plastic.
Very Best Choice: Mediterranean Tunnel
Made famous by Eliot Coleman in "Four Season Harvest", we swear by these little units as the most economical way to raise lots of food. This little 12' by 36' by 6' tall hoop house was built for 160 bucks, complete. It will last 6 years, and has already yielded 2000 pounds of produce in it's first year. All the hoops are made from 1 1/2" drop pipe that was taken out of old wells for pumps. They were just stuck in holes that were bored out by a bulb auger and then dropped in every 4'. I had the 2 x 4s on hand and ripped them in half to create the door jams which just hand off the first hoop. The white edging is a handy little item called "Cinch Strap", a polyethylene plastic sold on rolls, and was used to hold down the ag plastic. All other edges of the plastic were buried in the soil. Follow the photos below for the black clip attachment system.