Cut Tulips: Winter Income from High Tunnels
Many of us growing cut flowers in high tunnels harvest our final crop in early November (Zone 5), heave a sigh of relief, and relax until spring fever hits us in February. But during that period the tunnel sits empty, and its valuable space is not used. With relatively little extra work in the fall, we could increase our late winter income from that structure by growing cut flower tulips.
Two things are essential for such an enterprise: a high tunnel that will withstand the winter storms and a means of keeping the planting watered over the winter. For the former, check with your tunnel manufacturer for their winter guidelines. For winter irrigation, we need to assume that a trickle irrigation line could freeze on cold nights. We therefore need a way of easily shutting off and draining the water line needs that needs to be provided. With those factors in place, tulips are remarkably little work, and will yield superior quality stems about 3 weeks before they could be harvested from outside plots, depending on weather conditions.
We explored the potential of high tunnel tulips in the winter of 2008/9 at the urging of Dr. Bill Miller, head of the Dutch Bulb Research Program at Cornell. In that first trial, tulips planted directly in the tunnel soil about 4 inches deep performed better than bulbs in crates in the tunnel. In 2009/10, we investigated the effects of additional low tunnel protection within the high tunnel, and soil mulching on earliness and stem length, using 5 tulip varieties donated by Dr. Miller’s program. In early November, 2009, we prepared the plots by digging down about 5 inches and placing 35 bulbs of each variety in an area of 18 by 36 inches. Low tunnels consisted of number 9 wire hoops covered by a single layer of spun-bonded material (1 oz./yd2). A straw mulch about two inches deep was used as soil cover on some plots. All treatments were repeated in 3 places to avoid location effects.
As expected, the choice of variety made a big difference in earliness and stem length. ‘World’s Favorite’ was both early and tall, with a smooth deep orange calyx lined with yellow. Although later, ‘Strong Gold’ had a sturdy stem and a flower that stayed somewhat closed throughout the life of the flower. ‘Ad Rem’ looked like a later version of ‘World’s Favorite’, but was susceptible to petal injury by cold weather.
Among the treatments applied, the low tunnel hastened flowering by only two days, and had no effect on stem length (not shown). Straw mulch cooled the soil, delaying plant emergence, and delaying flowering by 4 days. Although at first glance a disadvantage, mulching was helpful to spread out the harvest over a longer market window. In addition, the mulch stimulated the plants to stretch, adding 3 inches to the stem length. One drawback of the straw mulch treatment could be increased mouse damage, if mice are already frequenting the high tunnel.
Our results indicate that producing cut flower tulips in a high tunnel can result in the production of high quality flowers in a small area. Although the flower harvest was compressed into a short period, selecting later-flowering varieties as part of the mix could extend the harvest period, especially when combined with straw mulch and low tunnel treatments.
Many thanks to Liza White and Andrew Hoffman for assisting in this experiment.