Bobbin attached to wire at top of tomato trellis.
"We'll be talking about indeterminate tomatoes today," Tom started out. The basic reason-- yield. Indeterminate tomatoes can yield 30-40 pounds per plant compared to about 20 pounds per plant from determinates.
High tunnel indeterminate tomatoes can grow to be 20 to 30 feet in length. "To support a massive plant like this you need a heavy duty trellising system," Tom explained. The standard is to run a wire cable eight to ten feet off the ground. The cable will be 3/32nd in diameter. To hold up to the downward pull of ten to twelve pounds exerted per plant, you want to run the cable off support poles, and should not attach the cables to your high tunnel structure. To connect the plant to the cable, growers use woven polypropylene string. This is not your standard "tomato string" from the produce supply place. It is heavier duty. Otherwise, as one grower noted, "after a while the string starts to break and every other day you are restringing a fallen tomato plant." The string is attached to the plant with plastic clips on one end and to a bobbin attached to the wire on the other side. After the plants reach their full height and the bottom fruit are picked, you prune off the bottom leaves every three or four days and let the plants down.
The standard for high tunnel tomatoes is a single leader. It is important to sucker frequently in the morning when the plants are dry. Pull up to snap off suckers, not down which can easily damage the plant, Tom explained. You will want to prune in the morning when the plants are dry. If you prune when it is wet, it is easy to move diseases like botrytis from plant to plant.
Did you know a tomato cluster can have ten flowers? For large fruit, clip off clusters to leave only three to four fruits, for small or medium leave four or five. This is also a chance to cut out cracked or misshapen small fruit that will just sap the plant's energy.
Tom showed us a few handy tools you will want to use in a tomato high tunnel. Did you realize that every time you lift a fruit up to the side to check if it has cracks or catfacing you may very well be crimping that stem to the point where it will never ripen properly after that? A little inspection mirror--it looks like a dentist's tooth mirror--allows you to look underneath the fruit without bending the stem.
I have seen good results from removing older leaves, even in the field, and so I was glad to hear Tom say this practice can be well worth the extra time it takes. For high tunnels Tom recommends you remove four to six of the bottom leaves every ten to twelve days to improve circulation after the plants reach the top of the cable. This is something you do right before you let the plants down from the bobbin. Tom reminds us that for problems like leaf mold, which can reduce yields significantly, that good air flow is essential. Leaf removal enhances air flow, reduces relative humidity in the canopy, and expedites the drying of foliage. Most importantly, leaf removal reduces the incidence of disease and allows growers to reduce fungicide usage on the crop.
Indeterminate tomatoes will require about five square feet per plant to maximize yields. Planting densities over one plant per five square feet will reduce yield per plant and may increase the risk of botrytis and leaf mold in the crop. Typically plants are set about four feet on center in double rows with a spacing of 14 to 16 inches between plants within the row.