It might be fun, from the standpoint of variety, to devote some of your greenhouse area to a few vegetables and herbs and practical, too, if you like bright red, summer-type tomatoes during the bleak days of winter, and gourmet seasonings for salads and stews.
The number and kinds of vegetables you grow is limited only by the amount of space you wish to devote to them and by the temperature requirements of the individual crops. Cultural directions are much the same for all: a rich, fibrous well-drained soil, though root crops such as carrots, beets, and radishes shape up better and are smoother in texture if a good bit of sand is worked into the soil mixture. They all like plenty of sun, and this is especially important when they are grown in winter under glass. Keep vegetables well watered after seedlings have been transplanted to their permanent locations, and a humid atmosphere is beneficial. A regular feeding every two to three weeks with a complete liquid fertilizer is important during periods of active growth.
Tomatoes will probably be your first choice, and one or two plants grown in large pots will undoubtedly be enough. If plantings are staggered over several weeks, you will have tomatoes available until well into spring, but the first sowing must be in July since fruit will ripen in a 60 F temperature only if it is well set on the vines before the short days of fall. Grow the plant to a single stem, staked for support. To assure that fruit will set, pollinate blossoms by hand, shake vines to fertilize the blossoms, or use a hormone-type tomato spray on the blossoms. I found it a simple matter to hand pollinate with an artist's small red-sable brush. 'Tuckcross O.' is a vigorous hybrid with smooth, meaty fruit, specially recommended for greenhouse forcing. You might try one of the small-fruit tomatoes, such as 'Tiny Tim', 15 inches tall with 3/4-inch tomatoes with a fine flavor; or 'Patio' with medium-sized fruit on a 2-foot vine (this one was developed for growing in limited space).
Bibb lettuce is an excellent companion for tomatoes, requiring the same 60 F temperature. Sow every two weeks from the first of September for a winter and spring crop, and transplant from the germinating medium directly into the bench, 6 to 8 inches apart. Give plenty of water. Try 'Bibb Forcing', 'Burpee Bibb' or 'Butter King' for well-formed heads of tender, tasty lettuce; or 'Grand Rapids Forcing' for a loose-leaf variety.
Radishes add crisp color to your winter salads if you have a growing area that will hold a 50 F temperature. 'Cherry Belle' is an extra-early variety. Make successive sowings from late September on, in a light and sandy soil. Do not crowd. Beets can be grown in a cool house, at 45 to 50 F. Plant about 3 inches apart in rows spaced 6 inches apart, and use when half-grown for best flavor. Tops are tasty as a cooked vegetable, too. Try 'Detroit Dark Red', 'Short Top', or 'Lutz Green Leaf; 'Winter Keeper' takes a little longer to mature but is popular for its greens.
Carrots grown in the greenhouse should be selected from such varieties as Burpee's 'Goldinhart' or 'Chantenay'—tender, sweet, and only about 5 1/2 inches long when fully mature. Other varieties may be selected if they are used when half-mature (benches do not have sufficient depth to grow 7- or 8-inch roots). When forced for winter use, carrots need a temperature of 50 F with bottom heat for best growth. Cucumbers may be grown under glass but they require a temperature of 70 F to germinate and at least 65 F to grow. You might try them if you plan to use your greenhouse all summer, and they can be started as early as the first of March under glass. 'Ball Early Hybrid' is an excellent variety for greenhouse growing. No matter what your favorite vegetable may be, those grown under glass can be picked at the peak of maturity, preferably just before using, for a fresher, sweeter flavor. And the fact that you can have them out of season makes them doubly enjoyable.
Your greenhouse provides an excellent opportunity to grow your own herbs. And nothing adds spice to your life, or to your salads and stews, like a bit of flavorful chive or basil picked fresh from your garden. Turn the everyday boredom of cooking into an interesting and exciting adventure and at the same time add delicate blossoms and aromatic fragrance to your garden.
Here is a listing of herbs that can do very well grown in your greenhouse - don't overlook the importance of these herbs to introduce variety into the greenhouse environment as well!