Growing Cut Flowers in the Unheated Greenhouse

A successful hoophouse planting of dianthus and delphinium

In the South and in mild coastal areas, some cool-loving flowers will grow all winter without adding heat to the hoophouse. In colder areas, the hoophouse provides just enough protection to grow these varieties very early in spring or later in fall than usual. Daylength may limit blooming for some varieties, but even flowers that won't bloom in the short days of winter can put on significant growth and be ready to send up stems as soon as the days get longer. Day-neutral flowers will bloom as long as the temperature is acceptable. Some of the top crops for hoophouse production in cool weather:

• Anemones, Dutch iris, freesias, and ranunculus are high-value cut flowers, grown from bulbs or corms. Tulips and narcissus can also fetch a handsome price, especially when they are of premium quality, less common varieties, and brought into bloom early.
• Ammi majus, bupleurum, campanula, delphinium, dianthus, digitalis, larkspur, lupine, snapdragon, stock, and sweet peas are seed-grown flowers that love cool weather.
• Single-stem sunflowers are a great crop for early spring, late fall, and even winter in mild areas. Grow day-neutral varieties such as the 'Sun' Series, plant them closely, and replant every two weeks for a long harvest season.

Hot Weather

Delphinium in the tunnel at Full Keel Farm, Fort White, Florida

Photo Credit: Full Keel Farm. All rights reserved.

It may get too hot for human comfort inside a hoophouse in summer, but some flower varieties can take the heat and even thrive on it. Be sure to provide as much ventilation as possible, such as by removing end walls, so that the hoophouse cools off at night. And pay attention to the plants' water needs they may require more frequent irrigation inside the hoophouse than in the field. Don't plant varieties that are prone to foliar diseases because the relatively still air inside the hoophouse may worsen the problem. Zinnias, for example, are more prone to problems inside than outside.

• In areas where summers get extremely hot, the best flowers for the hoophouse are celosia, lisianthus, and ornamental peppers.
• At higher latitudes, however, most summer flowers can be grown in a hoophouse. Delphinium, for example, will bloom repeatedly throughout the summer in a hoophouse.
• Lilies, too, can be planted sequentially for a long season of harvest.
• Annual dianthus such as those in the 'Amazon Neon' Series can be succession-planted for several flushes of flowers.