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Jesica Conrad/Master Gardener: Waiting around for those perfect tomatoes

Jesica Conrad, Beltrami County Master Gardeners

BEMIDJI -- We are all lusting after a homegrown tomato, one that smells like a tomato and tastes like one.

During early stages of development, the fruit continues to grow in size and remains green, typically requiring 40-50 days. Be sure you have selected tomatoes that can ripen in Minnesota. Once the fruit has reached full size (called "mature green"), changes in pigment causes the green to fade to light green then to the pigments for that particular cultivar, be it red, pink, yellow or orange.

Two factors that govern ripening and color development of tomato are temperature and the presence of a naturally occurring hormone called "ethylene."

The optimum temperature range for ripening mature green tomatoes is 68 to 77 degrees. When temperatures are outside this range for extended periods, conditions may become so stressful the ripening process halts. Tomatoes do not produce lycopene and carotene, the pigments responsible for ripe tomato color, when temperatures are above 85 degrees.

If frost comes early, tomatoes that have reached at least the mature green stage can be ripened off the vine. Look for a color change to at least a lighter green - and a little bit of blush is even better. Those that are still immature green will never ripen, deep-six those to the compost pile.

Store mature green to slightly blushed fruits at 60 to 65 degrees, or warmer if faster ripening is desired. Ripe fruits can be stored cooler, as low as 45 degrees. The typical home refrigerator is too chilly for storing tomatoes. Never, never put tomatoes in the refrigerator. Instead, pack fruits in shallow layers and keep in a well-aerated location where temperatures can be maintained and progress monitored.

Here are some ripening off the vine suggestions.

1. Reduce watering. If tomatoes have reached full or nearly full size, cut back on watering to encourage ripening.

2. Keep the plant dry. Late season is the perfect time for late blight to destroy fruit on the vine. Prevent it by watering the soil, not the plants. Keep plants from trailing on the ground, making them susceptible to diseases.

3. Remove the plant's lower leaves and any diseased leaves you see. More energy will go into the fruit.

4. Pinch off flowers. Removing them will focus the energy on the fruit already on the vine.

5. Pick off small immature fruit. The plant wants to focus on the larger fruit.

6. Pick excess fruit of the ones that are just ripening to allow the rest to ripen on the vine.

7. Pull slightly at the bottom of the plant to shift the roots. The tomato gets the signal that it is time to ripen on the vine and go to seed. There is a school of thought that says to cut a circle with a knife around the stem of the plant a ways away which does the same thing. I have never tried that.

8. Cover plants at night as temps dip. Ummm, might as well pick them, wrap in newspaper in one layer or pull up and hang upside down in garage or basement for ripening to happen.

9. Check your tomatoes daily when they start showing color. Remove those and the rest will ripen faster.

To find reliable information about vegetable gardening and other horticultural topics, go to the University of Minnesota Extension website at> Local master gardeners will also answer your gardening questions via a voice-mail service. Call 444-7916, leaving your phone number, name and the nature of your question. A volunteer master gardener will give you a call.