By mid-September to the end of September, everyone in our area should be enjoying the wonderful flavor of fresh, ripe tomatoes. Some of us wait 10 or even 11 months for this annual treat and it always ends far too early, usually with the first frosts. Unfortunately, some local gardeners are still waiting for their tomatoes to ripen as the days get shorter and cool nights slow down the ripening process. As I wrote before, tomatoes ripen the fastest at temperatures between 70 and 80 degrees. They will still ripen at 60 degrees and even a little lower, but much slower. To make matters worse, many tomato plants have already been pretty much defoliated by diseases such as late blight. The flavor of these fruits depends on the compounds, mainly sugars, which are made in the leaves. Many supermarket tomatoes are harvested in the green stage and then sprayed with ethylene gas, which makes them blush. These fruits have very little flavor, just like those of your bare plants. Prevent premature disease defoliation by spraying plants early in the season weekly with an organic or conventional fungicide. You can stop spraying by the end of July and still have protected the plants for much of the harvest season. If plants are losing their leaves to disease weeks after harvest, who cares?
So what is the cause and solution to the green tomato riddle? Well, it all starts with a suitable selection of varieties. All tomato varieties and most other vegetables have an “average” harvest time on the package. This date is based on when the plants are arranged in the garden from bundles of cells and it assumes that they are transplanted into warm soil that allows immediate root development. For those of us who live in the higher elevations of the Catskill Mountains, above 1,000 feet, our garden soils often don’t reach 70 degrees until mid-June. It doesn’t make sense to transplant to cooler soils, as I myself have experienced this season.
I set up 4 grafts of “Big Beef” on May 21st and four more from the same batch on June 5th, about 2 weeks later. The “Big Beef” would be ripe 73 days after transplanting. The first plants should have been ready to be picked around August 1st. It turned out that both groups of plants ripened their first fruits on the same day, August 7, despite the two week delay. Since then, I have picked red and ripe fruit almost every other day and now it looks like I will be able to harvest 90% of the fruit that formed before the frost. The “Beefsteak” tomato varieties ripen in 85-96 days, making them unlikely to perform well in my garden. “Brandywine”, a very popular heirloom variety, also takes 85 to 100 days. Even “Early Girl”, a berry variety, takes around 65 days to mature from transplant. So next year, be careful about what varieties you buy, especially if you live in higher elevations.
Most of you live in a warmer climate than I do, but some of you are not yet picking ripe fruit. There are a few other factors that contribute to late ripening. Perhaps the most common reason is nitrogen over-fertilization. Tomato plants that are given too much nitrogen will often grow very fast and very large, but plants that very happily grow vegetatively don’t seem to need to complete the reproductive process.
Many gardeners are guilty of over-fertilizing, believing that if a little is good, then a lot is better. This is true for both conventional and organic gardeners. Four pounds of 5-10-5 fertilizer is more than enough for about four to six tomato plants, growing to an area of about 10 square feet (100 square feet). Compost and manure have a fertilizer ratio of 1-1-1, so it takes five times as much to deliver the same dose of nitrogen. Twenty pounds of compost is sufficient for these plants. If you are using a concentrated organic fertilizer, like dried blood, which contains 12-15% nitrogen (12-1-0), you only need 2 pounds or less to feed them. Organic mulches, like straw as well as organic matter that is plowed into the soil, like cover crops, also add nitrogen as they break down. One acre of a legume, like alfalfa, when plowed in the spring, provides about 265 pounds of nitrogen the following season – almost 3 times more nitrogen than a corn crop needs! And corn needs a lot more nitrogen than tomatoes. So next year, forgo the fertilizer if you want ripe tomatoes in August!