Choosing Flower Crops to Overwinter: Trial Results
By the Hensley's flower team
The Hensley's team has run overwintering flower trials over several years in unheated high tunnels in a Zone 5 climate. This summary covers the results crop by crop, including our six top choices for beginners and a review of everything we've tested.
Top 6 Flowers for Overwintering in Tunnels
New to overwintering? Begin with one or more of our six best flowers for overwintering in tunnels:
These six crops have done well in our trials year after year, standing out for winter survival, stem quality, productivity and earliness compared with field plantings. If overwintering is new to you, see our getting started with overwintering flowers for how we do it.
Over 30 Flower Crops to Overwinter
Download the overwintering trial results by crop for notes on the more than 30 flower crops we've overwintered in our Zone 5 trials.
Once you're ready to go beyond the top six, start with our overwintering trial results by crop, a spreadsheet you can save and use for your own planning and records. It covers the 30-plus crops we've grown through winter in unheated tunnels, with details on:
- Sowing and transplant dates
- Survival rates
- Bloom window
- Harvest window
- Yield
- Recommended varieties
- Pros, cons and growing notes
Keeping notes on a winter tunnel crop is a cycle that never really stops: one season wraps up as the next begins. Soon after the summer solstice it's time to plan the next winter's flowers, and then come seeding, tunnel prep and transplanting in quick order. Good records repay the effort by helping you weigh costs against your system and markets, make better decisions and get better results.
Performance Recap: Flower Crops from Trials
Here is a closer look at the best performers in our overwintering trials.
- Agrostemma: survives winter very well and makes a vigorous, tall, early filler.
- Ammi/Daucus: strong, tall, straight stems and bigger flowers than field plantings.
- Bells of Ireland: survived every winter in our trials and produced very tall, thick, strong stems.
- Bupleurum: grows much taller than in the field; a great spring bouquet filler.
- Campanula: overwintering suits this daylength-sensitive crop, which needs short days to build stem length before long days trigger bloom.
- Cynoglossum: survives well in our tunnel and gives tall, strong stems.
- Dianthus (Carnation): the Sweet™ Series are among our very first spring bloomers. The Amazon Series and Chabaud Series follow a little later and do just as well in the tunnel.
- Digitalis (Foxglove): both first-year-flowering and biennial foxgloves do well in our overwintering tunnel.
- Eucalyptus: both 'Silver Drop'and 'Silver Dollar'survived reliably for us, growing to 8' by mid-July.
- Icelandic Poppies: these crops are vigorous and tough; they thrive in late winter and early spring and outperform spring plantings.
- Larkspur: we especially like the Galilee and the QIS™ Series.
- Lupine: both first-year-flowering and perennial lupines have come through winter very well for us.
- Matricaria (Tanacetum/Feverfew): a wide range of flowers on a very vigorous, productive plant.
- Nigella: full, lush plantings make it an excellent filler.
- Orlaya: tall, strong stems; a lovely filler.
- Persian Cress: a sturdy, productive, airy filler with intriguing shiny seed pods.
- Rudbeckia: a bright, cheerful, bold addition to early-summer bouquets, with big flowers on strong stems.
- Saponoria: brings variety and interest to early bouquets.
- Scabiosa: performs very well in the winter tunnel and has survived reliably in our trials.
- Snapdragon: does very well for us year after year and survives reliably.
- Stock: doesn't overwinter well for us in Zone 5, but does well planted in the tunnel in late winter.
- Sweet Peas: a great overwintered tunnel crop that needs strong support.
- Tulips: tunnel planting gives us 3–4 extra weeks, and we've had good results with Darwin hybrids, double early and double late, parrot and single types.
- Viola (Pansy): plants stay compact and bushy all winter (good for edible flower harvests), then stretch quickly as days lengthen, giving longer stems for cutting.
Learn More
- See all our flowers suited to overwintering
- Getting started with overwintering flowers: methods and recommendations from several years of trials
- Sowing dates for overwintered flowers
- Overwintering flowers webinar: stretching the season with cold-hardy annuals • FULL RESOURCES
- Overwintering trial results by crop • XLSX
- Overwintering trials • sowing date calculator • XLSX
- USDA hardiness zones • MAP
