Growing Cut Flowers in the Unheated Greenhouse
Lynn Byczynski grew organic vegetables and cut flowers for market before starting a magazine to help market gardeners across the country swap experience and know-how. The first issue of Growing for Market came out in January 1992, and GFM went on to become a respected source of practical, realistic advice on growing and selling produce and flowers.
Cut flowers rank among the most profitable crops for an unheated greenhouse (hoophouse or high tunnel). Even the modest shelter of an unheated hoophouse pays off in many ways: top-quality blooms, longer stems, fewer pests and a far longer harvest season.
Which varieties do best inside depends partly on your latitude and climate. Save precious hoophouse space for crops that struggle outdoors or can't be grown outside at all because of wind or late frosts.
Experimenting is the secret to growing great hoophouse flowers, since your climate and markets will determine what works best. Here are some general guidelines for choosing crops.
Cool Weather
In the South and mild coastal regions, some cool-season flowers will grow all winter in an unheated hoophouse. Farther north, the hoophouse gives just enough protection to grow them extra early in spring or later into fall. Day length may hold back flowering for some, but even flowers that won't bloom in winter's short days can bulk up and be ready to flower as soon as days lengthen. Day-neutral flowers bloom whenever temperatures allow. Top cool-weather hoophouse crops include:
- Anemones, Dutch iris, freesias and ranunculus, all valuable cut flowers grown from bulbs or corms. Tulips and daffodils can also bring good prices, particularly premium-quality, unusual or early-forced stems.
- Ammi majus, bupleurum, campanula, delphinium, dianthus, digitalis, larkspur, lupine, snapdragon, stock, and sweet peas are cool-loving flowers grown from seed.
- Single-stem sunflowers do well in early spring, late fall and even winter where it's mild. Choose day-neutral varieties, plant them close together and resow every two weeks for a long harvest.
Hot Weather
A summer hoophouse can be too hot for people, but some flowers handle the heat and even love it. Ventilate as much as you can, for example by taking off the end walls, so the house cools down at night. Watch watering too, since plants inside may need irrigation more often than in the field. Skip varieties prone to leaf diseases, because the still air inside can make them worse; zinnias, for example, tend to have more trouble indoors.
- Where summers are very hot, the best hoophouse flowers are celosia, lisianthus, and ornamental peppers.
- Farther north, though, most summer flowers grow well in a hoophouse. Delphinium, for instance, reblooms all summer under cover.
- Lilies can also be planted in succession for a long harvest.
- Annual dianthus, such as the 'Amazon Neon' Series can be succession-planted for repeated flushes of bloom.
Learn More
The Flower Farmer: An Organic Grower's Guide to Raising and Selling Cut Flowers
by Lynn Byczynski
- Forcing bulbs
- Forcing bulbs in soil: an introduction(article)
- Forced tulip bloom and chilling date calculator• calculator (XLSX)
- Forcing tulips(article)
- Picking tulips for forcing(article)
- Overwintering Flowers
- Overwintering flowers: methods and recommendations from multiyear trials(article)
- Which flowers to overwinter: trial results(article)
- Seed-starting dates for overwintered flowers(article)
- Overwintering flowers: stretching the season with cold-hardy annuals • webinar resources
- Overwintered flower trials: results by crop • worksheet (XLSX)
- Overwintered flower trials: seeding date calculator • worksheet (XLSX)
- Heat and drought
