A visit with Farmer Roger

The idea of a microclimate is one that good gardeners learn to utilize, even if they don’t know the idea by name. Tender plants do best in that area along the house that is sheltered and always warmer. Hostas grow in the shady spots, grass dies out. That damp spot in the back corner is bad for raspberries, but great for irises.

On the farm, where we are growing a large number of plants, we need ways to change the amount of heat, light, and water that our plants receive. Anything we do beyond sticking plants out the in the field and waiting for them to grow will cost us in time and materials, so you can be sure we wouldn’t use methods if we weren’t convinced the techniques paid us back for our efforts. The payoff may come in being the first to market, extending the growing season, providing some insurance against an unusual weather year, reducing weed competition, or even reducing plant disease. We’re not doing anything that couldn’t be done in a backyard garden. We’re just working on a bigger scale and with a smaller budget for each plant.

Low tunnels, drip line, plastic mulch, row cover, raised beds, hoophouses and shade cloth are the seven techniques I’m writing about today for manipulating the growing conditions around our crops.

Low tunnels act a miniature greenhouses, so tulips bloom earlier.

I took this photo a few days ago because it is such a graphic illustration of the effect of the ability of low tunnels to boost the growth of plants by gathering heat.  You can see that the tulips inside the low tunnel are blooming, while the plants outside still have quite a ways to go. Low tunnels are simple. Here Famai has used sections of irrigation pipe purchased at the nearby hardware store to make arches. He has draped plastic sheeting over the arches and buried the edges with soil. One advantage of using the pipe is that Famai can walk through the low tunnel and pick the tulips without disrupting the tunnel itself. In fact, Famai has already harvested half or more of the tulips in this low tunnel.

Low tunnels boost the growth of young plants.

This is the the type of low tunnel I like to use. The hoops are heavy gauge wire and the tunnels are much lower, significantly reducing the cost of the tunnel. I use the tunnels to protect the transplanted plant starts from cold nights and to give the plants a more rapid start. We remove the plastic once the plants start to flower or grow tall enough to touch the plastic. You can see that this plastic is perforated for ventilation. I used this type one year, but I much prefer plastic with slits for ventilation. The slits allow us to reach inside to hand weed around the plants. It turns out that low tunnels are also excellent for boosting the growth of weeds!

Supplying the right amount of water to the growing plants can be a challenge. Right now the soil in our fields is still mostly saturated with water due to the winter rains. However, it is surprising how little rain we receive in the summer. If we want our plants to thrive, we need to deliver water to the plants. Overhead sprinklers are tremendously wasteful of water; when the air is dry, most of the water never reaches the soil. In any case, hauling sprinklers and hoses over acres of fields takes up huge amounts of time that could be spent on other tasks.  We use drip irrigation wherever possible. Installing the drip system each spring takes up valuable time when we are already very busy, but once set up, we just need to open and close valves to control the water flow. Plus, the water is delivered directly to the soil, greatly reducing losses due to evaporation.

You can also see the black pipeline in the photo above. This pipe carries irrigation water along the edge of the field. At each row of plants you can see a tube branching off to deliver water to that row. The thin tubing has outlets at regular spaces. I like the 6-inch spacing. The tubing collapses flat when there is no water pressure, so it is commonly called drip tape.

Row cover fabric protects tiny plants. Onion starts do fine without.

I took this photo and the next when we were still growing vegetables for sale at the farmstand. The row covered with the thin white fabric has been planted in bok choy and other Asian vegetables. Row cover can serve some of the same functions as low tunnels, but without the hoops to raise the fabric off the plants. The row cover is thin and light enough to let the rain pass through. The fabric is laid loosely over the row, so the plants can grow, pushing up the fabric. Another major benefit of the row cover is that it blocks incoming flea beetles and other pests from reaching the plants. If you have seen tiny pinholes in Chinese cabbage, bok choy, arugula, or other greens then you are most likely seeing flea beetle damage.

The three beds to the right have all been planted with onions. All these were planted in holes punched through a very thin black plastic.  The black plastic gathers the heat from the sun, warming the soil below, and giving the plants a heat boost. Another major benefit is that the plastic blocks the weeds from growing, so we only have to weed where we have punched through the plastic. Last year the plastic mulch really paid off. In a difficult year for winter squash, our farm had much greater success than our neighbor farms.

Another advantage of the plastic is that it keeps the soil moisture from evaporating. Since the drip tape is under the plastic, all the water stays in the soil, available for the plants. Drip tape under plastic is even more efficient at conserving water than drip tape lying on the ground.

The plastic mulch is laid using a tractor-mounted implement that rolls out the plastic and covers the edges with soil to hold it in place. We have also laid plastic mulch by hand. The tractor is much faster, and does a better job, too.

A thin sheet of plastic warms the soil, giving the plants a boost.

This photo illustrates a number of techniques. The very front row is a red lettuce not long transplanted out. The next row looks like romaine lettuce. Behind that is a row of rainbow Swiss chard. The next row is spinach, followed by two rows of red or green lettuces, some ready to harvest.

Here you can see that the plastic is stretched over raised beds. We have a tractor-mounted implement that scoops up the soil to raise the level of the bed, while at the same time stretching the plastic mulch over the bed.

I like to use raised beds early in the season when we still might get a fair amount of rain. Raising the top of the bed those few inches lifts the plants up out of the puddles, so the roots are less likely to smother from lack of air. Also, it is amazing how much raising the top of the bed those few inches helps your back muscles when bending down to tend the plants.

In the background you can see several of our hoophouses. Hoophouses, also call low tunnels, are simple structures of plastic sheeting stretched over a framework of pipe. Typically we use the term hoophouses for structures that are not heated and where we grow plants directly in the ground inside. Usually we use hoophouses to extend the season, either to be early to market or past the early frosts. I’ve used one to grow bigger pumpkins than I can grow outside.

Here in the Pacific Northwest growing tomatoes in a hoophouse is an excellent way to prolong tomato production. In the fall when the rains start, the tomato plants outside typically get late blight and die in a few days. The organism causing late blight is splashed up onto the plant with the soil. Sheltering tomato plants from the rain and watering them with dripline lying on the ground may mean several additional weeks of tomatoes in years when the rains come early and the frosts come late.

We may add roll up sides to spill out excess heat on hot days. We may add a thermostat-controlled exhaust fan if we don’t want count on always opening the doors or rolling up the sides on time. We may add fans inside to move the air around to reduce the chance of moisture-induced fungal infections. We may add a second layer of plastic on the roof with a small fan blower to puff up the top layer and add some insulation. We may add a heater, but by that time we are calling the structure a greenhouse, rather than a hoophouse.

We use this hoophouse to grow plant starts for transplanting.

We also use hoophouses to start seedlings for transplanting out into the field. We can start the plants in the hoophouse before we would risk planting the seeds directly into the soil, and them transplant them out when it is a little warmer. If the summer is cooler than average, that extra growing time in the hoophouse may make all the difference in a successful harvest. Putting growing plants in freshly prepared ground also gives our plants an important head start over the weed seeds, which are sure to sprout in abundance. Except for the corn in the corn maze, we transplant most of the plants on our farm.

We have made a number of changes to this hoophouse to make it more useful as a starts house. We have put weedblock fabric down on the floor. This is not strictly necessary, but it does keep things tidier as well as keeping our feet out of the mud that would result from daily watering. We have put in tables to raise the plants to a better working height for us. We have added a greenhouse bench in the far corner where we fill the seeding flats with the seedling mix and poke a seed or two into each space. You can’t see them in this photo, but we have added roll up sides and a thermostat-controlled exhaust fan at one end. A hoophouse can heat up remarkably quickly on a sunny day. One afternoon of unexpected sun could kill off most of the tiny plants in the house in a few hours. That could mean that we could not grow those crops that year, resulting in a tremendous financial loss. Crop loss due to weather such as hail or windstorms is difficult to deal with. Loss due to forgetting to open the hoophouse doors would be much more painful.

When summer is in full swing, we have one more tool to moderate the hoophouse temperature. We add shade cloth over the house to reduce the temperature buildup.

Shadecloth is a woven material used to cut down light intensity.

Shade cloth is a loosely woven black fabric. It comes in various percentages in light blocking. I enjoy looking up through the fabric from below when the birds walk about on the fabric.

We use shade cloth to moderate hoophouse temperatures, but shade cloth is most commonly used to provide shade. Nursery growers routinely use shade cloth when growing shade-loving landscaping plants. When grown in an open field, some commercial crops, such as ginseng, are only successfully grown under shade cloth. Farmers in hotter regions have been successfully experimenting with using shade cloth to help them extend the growing season for cool-season crops such as lettuce and other greens further into the heat of the summer.

So, no big secrets here. No high tech. Nothing that couldn’t be used by any grower from a tiny backyard garden all the way to a huge farming operation. The only difficult calculation is whether using one of these techniques will pay back the time and effort to use it. And like so much else in farming, it all depends on this year’s weather.