Pick and ripen tomatoes when frost threatens

While warm weather can linger well into September along Colorado's Front Range, temperatures can also drop unexpectedly. The earliest September freeze in Denver occurred on September 8, 1962 when the temperature dropped to 31 degrees F. I’m certainly hoping for a warm fall but will be prepared to mount a tomato “rescue” if things look dicey.

Covering plants to trap heat from the soil is often enough to get through a short one or two night situation. Extended days of cold particularly when accompanied by cooling moisture (rain or snow) are more problematic. In those cases, harvest fruit before the frost event and ripen indoors.

Pick fruit with even a hint of color. Also harvest green tomatoes with a glossy green appearance that are at least three-fourths of their full size. Remove stems. Wash fruit under a stream of water and allow to air dry on clean towels. Make immediate use of any damaged fruit and save only blemish free tomatoes for ripening.

Low humidity causes fruit to shrivel while high humidity promotes mold. Pack fruit one layer deep in cardboard boxes in a room out of direct sun. Another option is wrapping individual fruit in sheets of newspaper or waxed paper if you have problems with shriveling.

Some gardeners have success with hanging whole plants upside down in a shed or basement to let fruits ripen gradually. In our dry climate, fruit handled this way tends to shrivel from low humidity.

Monitor fruit condition every few days. Remove fruit that has started to spoil before rots move to adjacent fruit. Ethylene gas produced by ripening tomatoes is a ripening hormone. Remove ripe fruit from the immature ones to slow ripening. Allow ripe fruit to remain to speed ripening of the rest of your tomato harvest.

Green fruit will ripen in about two weeks at 65 to 70 degrees F and about 3 weeks at 55 degrees. Storage below 50 degrees F will result in fruit with a bland, off-flavor. Never store tomatoes in the refrigerator if you want full flavor.

Photo credit: Range of tomato maturities on vine and Harvested tomatoes in box - Carl Wilson