We begin thinking about any spring planted crop the previous fall. Since springs tend to be cool and wet, all field preparation is best done in the fall. Field preparation may include chisel plowing for deep tillage, rototilling to help break down crop residue from the previous vegetable, laying down beds of black plastic, and coordinating and planting a winter cover crop to build soil health. While we try to use cover crops as much as possible, some of our fields are planted so early in the spring, perhaps with peas, carrots, or spinach, that there is no time to deal with the residue of a cover crop. These beds are then prepared in the fall but left bare for the winter.
Once our fields are prepared, we either direct seed or use transplants we've started in the greenhouse. If there is a week in mid-March when the ground thaws, Derek makes sure to get peas, carrots, and spinach seeded. These vegetables can germinate and survive even if cold weather returns with hard frosts. However, growth is very slow in the cold.
Transplanted crops give us a jumpstart, sometimes with nearly two months of growth. In our warmed greenhouse, we don't have to worry about cold temperatures inhibiting germination: little plants will pop up and grow steadily. Sweet corn germinates earlier than it would in the field and much more uniformly. It may seem odd to think of transplanting corn, but by using transplants we also avoid an early spring insect pest. Seed corn maggot is a juvenile of a fly very similar to the house flies you are familiar with. The maggots are active in very cool soils and they prefer to eat the large seeds of corn, beans, and peas. Since cool soils also slow the development of our vegetable seeds, often the maggots destroy the viability of the seed before the plants can emerge. Corn and bean transplants completely sidestep this hurdle.
So now that we've got little seedlings, and somewhat bigger transplants, growing in the fields, how can we protect them from freezing night time and cool daytime temperatures?
We spend somewhere around 50 person-hours each week deploying, handling, tacking down, lifting up, and re-tacking row cover. It is finicky, and it is frustrating to work with these sheets of thin fabric that are either wet, cold and heavy from morning dew or rain, or dry and dusty as the desert when we lay it out from the barn. But it is an essential component to early field production. Remay (as we call it) creates a warmer microclimate for the crops than nature can provide in the early spring (and in the fall, too). It holds two functions for us: protecting more delicate crops from frost, and pushing hardier ones to produce sooner.
For those crops that can tolerate a frost, the row cover is simply laid gently over the fields with soil holding down the edges, and the plants push up little humps as they grow. Corn, peas, lettuce, bok choi, chard, and beets all recieve this treatment.
Tomatoes, squash, beans, and basil need a higher level of protection. In their case, we use curved metal hoops anchored in the ground to hold the row cover away from the plants. This creates an insulated pocket of air around the foliage that will remain just those few degrees warmer when temperatures outside the cover are freezing. Despite this care, any part of these plants that touches the row cover during a frost will be frozen and die. So we spend hours working to get the covers in place neatly and without sagging, piling dirt along all the edges. Since these big pieces of cloth behave as giant sails, if the winds blow hard for a few days, we spend a few more hours fixing the spots that have been pulled loose. All this work is sometimes not enough, and during hard freezes, we will deploy a second layer of row cover just for the night.
We all breath a sigh of relief once we get through late May, and the threat of frost is usually past. Then we bundle acres of row cover into the barn to be used again in the fall.
We are also experimenting with two other systems to keep our tomato plants warmer as they grow. This is the first year we are trying short sections of low clear plastic tunnels. The plastic traps more heat during sunny days than the fabric of the row cover, so perhaps we will have earlier harvests.
The other system involves long clear plastic tubes, a foot in diameter, each filled with water. These tubes run along the beds, next to the tomato transplants, and beneath the hoops and row cover. The hypothesis is the water in the tubes will be heated by solar radiation through the day, then radiate the warmth at night onto the nearby tomatoes. This "water tube" experiment is one we've been conducting for many years, and we do have some of the earliest field tomatoes around. Whether the water tubes are the deciding factor, or it's due to the fact that we transplant our tomatoes in mid-April, we are still unsure.
So during the spring, as we seed, plant, weed, water, till, lay plastic, set up irrigation, clean the packing shed, barn, and chicken house, check over tractors and equipment for the coming season, sharpen shovels and hoes, spread manure and compost, mulch our perennial plants, and spread straw over the strawberries, we are also protecting our most tender plants, while we watch the sky, and test the breezes, hoping for summer but planning for frost.