Last season I grew tomatoes on straw bales and was rewarded with a terrific crop. The technique is easy. If you have a greenhouse, it is a great way to get early tomatoes without going to the store.
The first job is to buy one or two straw bales. Make sure you get straw bales, not hay bales. Hay bales will probably warm up faster, but they will also drop a lot of seeds in your garden patch as they decompose.
The best kind is held together with wires rather than twine. Twine tends to rot down and the bales fall apart. Set the bales where you want them and soak them. I left mine outside during the spring rain for a week – this was early April, after all. I moved the wet bales into the greenhouse and poured two cups of highnitrogen blood meal, one cup of high-calcium bonemeal, and one cup of triple superphosphate over each bale and hosed the bales down to help the nutrients soak in. Each day I soaked the bales and took their temperature. After a week the temperature had risen to 125 degrees in each bale. Now it was time to plant.
I piled a bucket full of compost and potting soil on each bale. Other gardeners say to excavate the middle of the bale and put the soil in the hole. This helps to limit runoff when you water. But never having tried this before, I poured the dirt on top. (If I do it again, I will make a square wooden frame from furring strips to contain the soil.) I set tomato plants in the soil and kept watering daily. I also set two plants in the garden soil directly in front of the straw bales as control plants. This was on April 17 and the ground still showed frost outside the unheated greenhouse.
Because I watered daily, both the bale-grown plants and the ones in front of the bales grew fast. The straw-bale plants, aided I think by the warmth in the bales, grew quickly and set fruit in mid- May. The in-ground plants set fruit in early June. I picked the first red tomato (Early Girl variety, not very big, but tasty) on June 7 from the straw-bale plants and kept picking right through the season. As of the middle of October, the vines are still producing juicy red tomatoes. Last year I was able to pick tomatoes from the greenhouse plants until Christmas. I am not sure if that will happen with the straw-bale tomatoes.
Would I do it again? I think so. The plants began growing early in the greenhouse and kept right on producing late in the year. The only problems I found were that mice got into the greenhouse and tried to nest in the straw bale. Also, the straw bales raised the plants about 14 inches off the ground, so when they grew upwards, they hit the greenhouse roof and spread out into a huge clump that became difficult to get around.