It’s a beautiful, sunny morning in late May as I write this column in Webster, New York.  You may be wondering, “Webster, New York?  I thought Dave lived in Maryland.”  Well I do live in Maryland.  I always have.  I’m in Webster to visit my friend Susie who retired last summer after 30 years of teaching in Maryland.  This trip was in the works last summer when Susie moved to New York to share her new house with her mom, Edna.  She moved back to the Rochester area to a new home in a retirement community, complete with a yard of nothing but grass.  There were no shrubs, no trees, no perennials— nothing but grass from the house to the street.  My partner Chuck and I offered to landscape her new property last summer.  But as summer turned to fall, we realized we couldn’t make the time to travel to upstate New York to get the work done.                  

This spring we checked our calendars and came up with three days at the end of May that would become “Garden Time at Susie’s.”  Chuck and I flew up Saturday after the farmers’ markets were finished and the flowers were picked for Sunday’s market. (The Sunday market was understaffed, but capable employees kept the line of customers under control.)  We boarded the plane with our usual carry-on bags as well as an oversized bouquet of Laguna lilies for our hosts.  We spent Sunday shopping at some of the nicest garden centers I’ve ever visited.  The plants were plentiful and nearly perfect, there was always a knowledgeable employee or two within sight, and those employees were eager to help find plants or answer questions. We had dinner Sunday night at a restaurant overlooking the Erie Canal with Susie, and her mom and Aunt Jane, both ladies in their 80’s.   It was fun to hear Aunt Jane lecture Edna to not use the word “old” when talking about themselves.  As in 85 years old.  After dinner, as we gave Aunt Jane a huge bouquet of Laguna lilies to take home, her eyes sparkled with delight.            

Monday was spent planting the more than 160 trees, shrubs and perennials we purchased the day before. Our friend Susie isn’t a gardener.  She likes the look of a nice garden, but doesn’t enjoy tinkering in the garden pruning, deadheading or watering.  The plants we included were all low maintenance, and easy  to care for.  We even included soaker hoses and timers to ensure the garden would be the talk of the neighborhood long after we were gone.  After another half day of planting, the gardens were finished and we headed to Rochester’s Lilac Park to research possible varieties to grow.

So, you may ask, what’s this all got to do with the ASCFG?  Well, here are a few things I was reminded of during my trip:

• Make time to spend with friends and family.  Don’t always work seven days a week. Trust your employees to do their job.  You can always be just a phone call away.

• Brighten someone’s day with flowers.  Whether for someone you know, or a child at the farmers’ market, surprise someone with flowers.  If you have extra flowers, give your customers a few extra stems. They’ll remember your generosity.

• Give your customers what they want.  Quality products, helpful service and a smile are things that can help your company thrive.  Enjoy your work, or get a different job.

• Always be on the lookout for new things to grow.  New offerings may keep customers excited about what you grow. You never know where you’ll find the next flower that will help pay your bills. (We all know, the ASCFG is a great place to start.)

• Don’t use “old” to describe people.  You’re an experienced flower grower, he was your former boss, she is a senior lady.

• Follow through on your promises.  If you offer to help some-one, follow through. If you tell a customer you’ll have a flower on a certain date, do your best to have it for them. If you’ve said in the past that you’ll make it to the ASCFG Conference “next year” then I guess I’ll see you in Raleigh.

Growers from Maryland, New York, Pennsylvania and Virginia exchanged information on high tunnel production at a recent seminar in Maryland.  If you are not presently growing in high tunnels you should look at what the benefits would be to your operation.  I thought I would pass along some of the information generated during our meeting.

You can construct a good quality high tunnel for around $1.50 – $2.00/sq. ft. of production area.  It does not take long to pay for the tunnel if you have the market.  This is a reasonable investment if you want to serve both early and late markets, and produce a better quality product in the rest of the season.  No doubt about it, you can generally generate more cash, compared to summer sales, from cut flowers in early spring or in October through December.  Several growers attending the seminar commented that they produce lisianthus under high tunnels for better quality (especially dark purple cultivars) and longer stem length.  Most are growing the lisianthus in raised beds in the high tunnel.

Day-neutral sunflowers do well in high tunnels but you need to interrupt the night with 2 hours of incandescent lighting to produce longer stems and better flower yield.  Snapdragons perform very well in high tunnels as long as you have a good netting system that holds stems straight to prevent them bending.  Dave Dowling was growing eucalyptus in high tunnels and it appeared to fare well in this protected environment. Plants growing outdoors had heavy winter injury while the plants growing in the high tunnel were vigorous and looking good at the end of May.

One cut flower that does not seem to benefit much from growing in a  high tunnel is sweet William.  Some of the southern Maryland growers who tried both field and high tunnel production of sweet Williams said that both came into cutting stage about the same time, without detectable differences.

A question that came up in the seminar is whether you should use single or double layers of plastic film over the high tunnel structure.  Most growers agree that having two layers is preferable and will keep the plastic from beating against the metal structure and fatiguing the plastic.  The layers can be inflated using a small squirrel cage blower.  When you cover a high tunnel with plastic, pick a warm day with no wind.  Stretching the plastic when it is warm makes a tighter fit when it cools down and the plastic shrinks.  Several growers reported that pulling the plastic when the metal bars are wet is difficult so pull it when the metal is dry to get the plastic to slide over the structure.  Most growers were reporting that they like using wiggle wire with u-channel to anchor the plastic to the end bar and the baseboard of the structure.

Quality of Construction

One point that we did hear from the experienced high tunnel cut flower producers in attendance was that new growers considering trying high tunnels should not use cheaply constructed pipe frames and single layers of plastic covering.  The poor quality pipe high tunnels have a reputation for costly repair after major storms. It is highly recommended that you select a strongly constructed high tunnel frame.  Having 4’ high straight sidewalls improves the usable space and makes operation of equipment within the greenhouse easier.

Several people tried to cut costs using untreated ultraviolet (UV) resistant plastic to cover their greenhouse.  A construction grade, untreated plastic holds up several weeks to a couple of months before it falls completely apart.  The inner layer of plastic can be purchased with a coating that keeps the inner layer from dripping condensation onto your plants.  This is a worthwhile feature to consider when buying the inner layer of plastic cover.  Use greenhouse quality UV-blocking/resistant plastic for your coverings which can be obtain form greenhouse supply companies. You can usually talk with manufacturer representative and see samples at nursery trade shows such as OFA in Columbus, Ohio in July or at the MANTS show, held in early January in Baltimore.


Tunnel Bugs

The question that comes up is whether there are fewer or more bugs in high tunnel production.  Back in 2004 David Dowling noted that zinnias growing in his high tunnels had practically no Japanese beetle injury while the same cultivars of zinnias growing just outside of the greenhouse had lots of damage.  We set up an evaluation trial of injury to zinnias grown in fields compared to high tunnels.  In 2005 and 2006 we evaluated damage to foliage and flowers of field-grown ‘Blue Point’ zinnias compared to the same selections grown in a high tunnel.  We found Japanese beetles prefer to feed on the plants in the field, causing 50-70 % injury levels to foliage while the zinnias in the high tunnels had less than 5% injury to foliage.

One interesting thing we found is that field-grown zinnias had a high incidence of bacterial leaf spot, while those in the high tunnel were relatively clean of the disease.  Keeping the water off the foliage makes a big difference in dealing with bacterial leaf spot, which is spread by free water on foliage.

What about other pests?  Are they in greater or lesser abundance in high tunnels?

One insect group that thrives in the protected environment of high tunnels is aphids. If you grow snapdragons and sunflowers in high tunnels you will probably have to control aphids.  Monitor regularly and when a hot spot is found treat the infestation.  Materials such as azadirachtin (Neem), imidacloprid (Marathon), acephate (Orthene, bifenthrin (Talstar), and TriStar  can be applied.

If you have thrips-prone cut flowers such as gerbera or lisianthus, high tunnels  will not protect you from the onslaught.  Materials to control thrips including spinosad (Conserve), Novaluron (Pedestal), and azadirachtin (Neem).  Two-spotted spider mite loves the warm conditions in high tunnels and if you are growing crocosmia you can almost guarantee that you will have to deal with spider mites. Abamectin (Avid), chlorfenapyr (Pylon), hexythizox (Hexygon), horticultural oil, and pyridaben (Sanmite) can be used in high tunnels for mite control.


Foliar diseases are reduced in high tunnels if you use trickle irrigation and keep the foliage dry.  The one disease that will be a problem in high tunnels is powdery mildew.  We generally see this on dahlias,  sunflowers and monarda grown in high tunnels.  Hydrogen dioxide (ZeroTol), horticultural oils, and neem oil can be applied to foliage to deal with this disease.

Production Notes

Tulip We planted in October, using 200 bulbs from 10 varieties.  Bulbs were planted 3” on center.  Half were planted 6” deep and half 8” deep to stagger bloom time.  Applied Treflan pre-emergent in October to prevent weed problems.  The deeper planted (8”) bulbs flowered 5 days later than 6” depth.  Stems on 8” deep tulips were longer.  Sprouted a week after high tunnel was moved over them and  in bloom in 3-4 weeks.  Harvested over a 5-week period (early and late varieties) including Easter market.

Peony Planted in October, two-year-old plants under tunnels produced blooms 2 weeks before field peonies.

Phlox Phlox under high tunnels bloomed same time as field-grown.  ‘David’ planted in fall in tunnels continued production into late fall.

Lisianthus  Planted in tunnel mid-April, harvested in mid-June.  Quality was excellent under high tunnel, much better than field-grown plants.

Salvia leucantha Native to warm areas of the world.  Short-day flowering initiating plant.  Easily rooted by terminal cuttings taken before flowers buds are formed. Roots well in sweat tents rather than intermittent mist.  Spacing can be as close as 15” or as wide as 3’. Wider spacing results in more stems per plant.  Harvested in mid-September to late November.  Plants are woody at the base but secondary flower stems are slightly brittle.  At Farmhouse Flowers the plants branch and bloom for 8-10 weeks in the fall.

Eucalyptus   Eucalyptus grows best in the heat of the summer. The high tunnel keeps temperature high enough that harvest is extended into November.  Harvest summer through late November.  Plants need some winter protection to survive.

Sunflower    Pick a sunflower that is listed as day neutral. ‘Sunbright Supreme’ works well.  Sequence plant sunflowers, beginning in late summer, starting a new set every 7 -14 days for continuous supply.  Late summer-planted flower heads tend to be one half the size of sunflowers grown in high tunnels in the spring.  In high tunnels, production of sunflowers should continue until the end of November.

Cosmos Start from seed.  Production continues through late fall.

Dahlias ‘Karma’ dahlias were planted in early June.  Harvest started in mid-August and will continue through the end of November.

Ageratum ‘Blue Horizon’ is well suited for high tunnel production, which will extend harvest through November.

Celosia Light frost kills celosia.  Plant in late spring, harvest in summer.  High tunnels will extend harvest into fall.

Visit other growers using high tunnels and see what they found works and what does not. If you are in Maryland and wish to visit some growers with high tunnels send me an e-mail at [email protected] or call (410) 868-9400.

Stanton Gill is Regional Specialist in IPM for Greenhouses and Nurseries, University of Maryland Cooperative Extension and Professor with the Landscape Technology Program, Montgomery College.