WHAT TO DO IN THE GARDEN: Nights in the high 30's this week. Live Boston.com Gardening Chatroom Friday 1-2 p.m.with Carol Stocker

Night temperatures are predicted to drop into the high 30's starting Wednesday night. Bring indoors temperature sensitive tropicals you want to try to save from cold, especially fibrous plants such as begonias, impatiens and coleus, before then.

The average date for the first frost for Boston falls on Nov. 6, though we could get our first frost anytime between Oct. 12 and Nov. 20, according to the National Climactic Data Center. The average first frost falls a little earlier, typically on Nov. 1, in Middlesex county.

As warm days begin to yield to cooler evenings, cool-weather vegetables (lettuce, spinach, etc.) and flowers begin to thrive. But many plants will need protection against cold nighttime weather.

A light freeze, from 29°F to 32°F, will kill tender plants but will have little destructive effect on other vegetation. A moderate freeze, from 25°F to 28°F, will have a widely destructive effect on most vegetation, with heavy damage to fruit blossoms and tender and semi-hardy plants. A severe freeze, 24°F and colder, with result in damage to most plants.

Here are a few steps that you can use to protect your tender plants against freezing temperatures to extend your growing season:

Find out the average first frost dates for your area. You can type in your zip code and get helpful info here: http://davesgarden.com/guides/freeze-frost-dates/
Have an outdoor thermometer handy, and check it often.
Check weather reports for forecasts of low temperatures.
Water the soil around your plants; moist soil retains heat better. DO NOT spray water on the plants themselves.
Cover your plants overnight. There are many good, lightweight plant covers available, but old bedsheets will do. Remove the covers during the day if it is warm and sunny.

Don't wait until the last minute to start bringing your less frost tender potted plants indoors. As the weather cools down, the difference between indoor and outdoor temperatures widen, making it more difficult for plants to adjust to the big change in temperature when you bring them inside.

Here are some other tips to make sure your plants successfully make the transition from outdoor to indoor:
Bring in only healthy plants. Unless you are planning to run a “plant hospital,” say goodbye to the struggling plants.
Check plants for diseases and pests. Problems tend to spread quickly indoors from plant to plant.
Spray plants with an organic insect control. Even if you don’t see them, insects such as aphids and spider mites can hitchhike on your plants—and then infest your healthy houseplants. Use a horticultural oil, such as Summit Year-Round Spray Oil, which contains no harsh chemicals yet is effective against a wide range of insect pests.
If you have room, bring in a pepper plant or some tender flowering perennials to extend your growing season.
Give away healthy plants that you don’t have room for inside.