Crop Rotations for Cut-Flowers in the Tunnel

Planning crops is hard when a small flower farm has little room to work with. The Hensley's team asked several growers how they plan greenhouse and high tunnel plantings, including how they:

• Get the most out of their growing space for bigger harvests and steady rotations
• Build and protect healthy soil
• Keep pest and disease problems down

We talked with five cut-flower operations. Every one of them described crop planning as a mix of art and science that always has room for improvement.

• An Oregon flower farm and nursery, run by a husband-and-wife team and their grower (Zone 8b), in the Willamette Valley
• A Washington flower farm, owner-grower (Zone 8b), north of Seattle
• The Hensley's team's flower trial program (Zone 5b)
• A Washington urban micro-farm, owner-grower (Zone 8b), on the Kitsap Peninsula
• A Vermont flower farm, owner-grower (Zone 4), in northern Vermont

Rotating Crops Between 2 Unheated High Tunnels

Our flower trial program grows a long list of crops and varieties in a small amount of tunnel space, much like a typical flower farm. Here is a look at how the trial manager fits a season's rotation into limited room in a Zone 5b climate.

Two 30' x 96' high tunnels make room for three short growing windows: fall planting, spring planting and summer planting.

High Tunnel #1

• Fall planting (harvest in spring and early summer): In October, the first tunnel is filled with cool-season flowers that bloom from mid-April into June. When they finish, the beds are turned over in late June for summer plantings.
• Summer planting (harvest in fall): Crops set out from June to early August bloom in September and October. This stretches the season and keeps high-quality stems coming after the first frosts that can end outdoor production. Both warm- and cool-season flowers go in for fall cutting, such as celosia, marigold, zinnia, stock, snapdragon and dusty miller.

High Tunnel #2

• Early spring planting (harvest in spring and summer): The second tunnel is planted in early March, as soon as the soil has warmed enough. It often holds flowers that like a long cool spell but will not reliably survive a Zone 5 winter from a fall planting, such as stock and ranunculus. These beds bloom from late May through June and add to the hardier overwintered flowers coming from the first tunnel. Lisianthus also goes into the tunnel in early spring. It occupies its beds all summer and flowers from late July into early September. In August and September those beds are cleared for the next round of fall-planted, overwintered crops, which brings the cycle back to the October planting described above.

Working between two tunnels leaves time to turn beds over between seasons, gives the soil a short rest between crops and helps break pest and disease cycles.

Rotating Crops Between 3 High Tunnels

At this Zone 8b farm, the grower uses raised beds inside three unheated 26' x 48' high tunnels and rotates plantings among them to keep yields high. The beds run crosswise off a center aisle, a layout that keeps crops out of wet conditions. She notes that lisianthus, ranunculus, anemones and heirloom mums are not especially demanding, but they dislike wet feet. She could grow them in the ground under caterpillar tunnels, but the high tunnels give her more control, and the raised beds add a few degrees of warmth.

Her year starts in February, when one tunnel is planted with ranunculus and another with anemones. She plants densely, setting corms closer together than the commonly recommended spacing, which she finds greatly increases her harvest. The tunnels also let her steer bloom timing, so she often has ranunculus ready for Mother's Day.

When the early bulb crops finish, the anemone beds are replanted with lisianthus plugs and ranunculus beds are replanted with rooted mum cuttings. Once the mums wrap up in late November, the soil rests until February. Splitting the season into two cycles this way has worked well for her.

In the third tunnel she alternates sweet peas with more heirloom mums. In her experience, the first year's crops roughly cover the cost of the tunnel, lumber for the raised beds and soil, and profit starts in year two. Unlike open ground, though, tunnels and beds need ongoing spending on upkeep every few years.

She believes a smaller farm with a single tunnel could adapt her approach and grow an even wider range of flowers than she does. One tunnel with a dozen or more raised beds could hold a whole summer's worth of flowers, mixing focal blooms and fillers that are each replanted for two successions.

Rotating Crops Between High Tunnel & Field

This Vermont grower also leans on high tunnels to lengthen her season. Her tulips are split between the tunnel and the field. After a busy spring that peaks at Mother's Day, demand from market shoppers drops in July and August, partly because many Vermonters grow their own cutting gardens. Business picks up again from late August into fall with custom and DIY wedding orders. Her spring tunnel shifts over to fall chrysanthemums. She keeps a detailed planting schedule in spreadsheets, while accepting that real life often changes the plan.

Besides the tunnels, she farms one large annual field, about 100 by 120 feet, split into two halves. Each year the halves trade places, so dahlias go where annuals grew the year before, and the rotation continues the next season.

Rotating Crops on the Micro-Farm

The smallest farm we spoke with is a Zone 8b micro-farm on less than a fifth of an acre in a city neighborhood. It has five unheated covered raised beds and a set of bulb crates, and still supplies flower subscribers from early spring through fall along with à la carte wedding flowers.

Planning starts in fall and mostly means swapping crops as seasons change and planting densely. In mid-November the grower fills fabric-lined crates with hundreds of tulips, daffodils and alliums. In January she begins winter and early-spring successions: pre-sprouted ranunculus and anemones go into covered raised beds outdoors, while hardy annuals (snapdragons, rudbeckias, stock, and sweet peas) are sown indoors in trays and moved out a few weeks before her usual last frost in early to mid-April. More rounds of spring bulbs and hardy annual transplants follow. By Mother's Day the bulbs have finished and the crates are emptied. She then sets out warm-season annuals started indoors in February, such as zinnias, cosmos, amaranth and celosia, and at the same time direct-sows a second succession of zinnias and cosmosin the raised beds.

Staggering Plantings with Seedlings, Plugs, and Root Cuttings

Combining several ways of starting plants, including seed, purchased plugs and rooted cuttings, helps a grower make better use of both limited propagation space and limited bed space.

The Vermont farm covers about one acre, with two 30' x 80' high tunnels and a 17' x 24' propagation house, plus cold frames for chrysanthemum cuttings. The season opens with anemones and ranunculus started indoors and moved to the tunnel, along with stock and other cool-season flowers such as bupleurum and snapdragons. When those finish in late June and July, the grower plants rooted mum cuttings, fall stock, and fall celosia seedlings, choosing seedlings or plugs based on cost and availability.

The Washington farm uses a similar mix, growing lisianthus from plugs and mums from cuttings, and starting other crops from seed.

Filling the Gaps

The Oregon farm has about three acres of production split between covered and open areas. It grows in raised beds inside a 100' x 30' heated high tunnel and in outdoor raised beds that can be covered with caterpillar tunnels when needed. Display gardens around the property inspire visitors at events and workshops, and plants that do not sell as cut flowers go into those gardens or the nursery.

Small farms often have two or three different flowers in one tunnel row. A large grower might cut and replant uniform 100-foot rows all at once, but here a single row might hold anything from butterfly ranunculus to some poppies and pansies. Because those crops finish at different times, it is hard to pull one and replant just that spot.

Mixed rows take more hand labor, while single-crop rows can be turned over with machinery. Without planning for the gaps, you may have nothing ready to plant, and the Oregon grower sometimes falls back on direct seeding.

Their grower keeps extra transplants on hand to slot into short sections that were not calculated correctly, such assweet peas, snapdragons, ranunculus, anemones and a small batch of poppies.

Small-Batch Cover Cropping in the High Tunnel

Bigger farms can rest whole sections now and then, but small farms often cannot afford that. Because the soil is asked to do so much, the Oregon farm stays on top of amendments. When a tunnel crop is struggling, they pull it and sow a cover crop, which grows quickly under cover and can still be cut and turned in. They also add an organic nitrogen or phosphorus amendment, such as blood meal or bone meal, each time crops rotate.

Cover-cropping one row at a time keeps the rest of the tunnel producing. Resting a whole tunnel, the way some farms rest a field for a year, is not affordable for them. Since their heaviest planting is in spring, they may put a few rows into cover crops over summer, often using an organic peas and oats mix.

Adding Compost for Soil Health

The Oregon farm also brings in plenty of compost, on the principle that good flowers start with good soil, especially in the high tunnel.

The Washington grower amends her soil with a quality organic fertilizer and compost, noting that every crop removed, such as spent bulbs, takes some soil with it. Her beds began with a custom organic three-way blend of native soil, sand and composted wood products. She limits the wood portion, because too much can tie up nitrogen as it breaks down and leads to extra amendments.

High Tunnel Pest & Disease Management

At the Oregon farm, crops move every year, even just to the next row, to cut down on disease. Good records help you remember to shift each variety's location from year to year.

Small growing spaces need close watching for pests and disease. The Washington grower releases beneficial insects such as lady beetles and lacewings starting in early spring. In a tunnel, everything is concentrated, so aphids must be dealt with quickly. She relies on predators first and, if spraying is needed, uses products approved for organic production that are gentler on beneficials. Densely planted mums can develop powdery mildew, which sometimes calls for a labeled copper product.

Takeaways

These steps can help a small flower operation get more out of its space.

• Work through the calendar and map out cool-season and warm-season crops. Keep good records so you can compare how your best sellers performed in past years. Build the plan around the flowers that earn the most, then fill in with the staples you need for bouquets. Use any unexpected open row or bed to trial new varieties.
• Set a regular soil-care routine. Plan to add compost, mulch or organic amendments before each main seasonal planting. Investing in the soil of a small area sets your crops up to do well.
• Try cover-cropping small sections so soil is not left bare, or cover beds with tarps between crops to reduce weeds.
• Even a cut-flower farm can grow some food. The Vermont grower keeps a spot in the middle of her tunnel for winter kale, spinach, beets and carrots.

Learn More

• 5 Cool Flowers to Plant Now • Secrets for Growing Hardy, Cool-Season Annuals • Article
• Part 1: Introduction to Overwintering Flowers: Methods & Recommendations from Multiyear Trials• Article
• Part 1: Introduction to Forcing Flower Bulbs in Soil• Article
• Succession Planting for Cut Flowers • Your Seed Chronicles: Planning & Planting for a Steady, Abundant Flower Harvest • Article
• Succession Planting • Ways to Keep a Continuous Supply • Article
• Succession Planting • Interval Chart for Flowers • CHART
• Succession Planting • Recommended Flowers • Table