How to Choose Cut Flower Crops: A Selection Method With Zinnia as the Test Case

What to take away

Start with the sales window, then score the crop

Pick a crop because a buyer wants it in a specific week, not because it is easy to grow. Kansas State lists the traits of an ideal cut flower: low cost, high value, high yield per square foot, a long season, a vase life of at least 7 days, heat and drought resistance, 18-inch stems and easy harvest (Kansas State University, MF1034). The guide says no single plant meets every criterion. They are a yardstick.

Editorial suggestion: score each candidate from 1 to 5 on five questions, then compare totals.

Score only crops with local evidence. If no one near you has grown a crop, give it a trial plot instead of a score. Kansas State advises a test plot first, to learn whether a plant is suitable and economical before expanding, and Virginia Tech says to introduce other species on a trial basis (Virginia Cooperative Extension, Publication 426-618). A first-year grower should read the bed planning guide before filling a crop list.

Compare annuals, perennials, bulbs and woody stems

The classes differ most in how long they take to pay back the bed.

A mix usually works better than one class. Annuals carry the first year, a small trial of bulbs or perennials fills the shoulder weeks, and woody plants wait until land tenure is secure. For the crop-specific cases, see snapdragon, sunflower, zinnia and dahlia compared.

Annual hardiness matters for timing. University of Illinois Extension separates hardy annuals, which tolerate cold soil and light frost (snapdragon is an example), from tender annuals that need warm soil and air (zinnia is an example) (Illinois Extension, annuals). For perennials, the USDA Plant Hardiness Zone Map is based on average annual extreme minimum winter temperature in 10-degree zones, with 5-degree half zones. It shows whether a perennial or woody plant is likely to survive winter. Use your frost dates for planting; the zone and calendar guide shows how.

Worked example: zinnia

Zinnia fits the method because it is a warm-season annual with documented trial data. Utah State University Extension describes it as frost sensitive, best transplanted after the last freeze, and responsive to trellising, moderate fertility and frequent harvest (Utah State University Extension, CutFlower/01).

Sales window and spec. Utah State puts florist-grade stems at 12 inches minimum and 18 to 24 inches preferred, with a vase life of about 7 to 10 days for most varieties. Zinnias are cut just before blooms are fully open, when at least two rows of petals have expanded and the upper stem is mostly stiff. Utah wholesale prices at the time were 25 to 50 cents a stem, and trial zinnias sold for $1 a stem in Wasatch Front markets. Treat those as Utah figures from 2020, not as a forecast for your market.

Cultivar choice. In Utah State's shaded high tunnel trial, plants were spaced 12 inches apart in 4-foot beds:

The authors named State Fair the highest yielding with the fewest culls. Cupcake gave low yields and high culls, and Pompon had high yields but the highest cull rate. Kansas State also lists State Fair among the best large-flowered zinnias. A field planting of 'Benary's Giant Salmon Rose' in the same publication gave 5.8 marketable and 8.1 cull stems per plant, a cull share of 58 percent against 44 percent in the tunnel. The two studies were not replicates, so compare patterns, not exact numbers.

Bed weeks and yield. Four plants per bed foot at 12-inch spacing in a 4-foot bed, times the table above, gives about 22 marketable stems per bed foot for State Fair and about 6 for Cupcake over the trial season. This is arithmetic on one Utah trial, and a different site will differ.

Spacing, pinching and support. Utah State recommends 9 by 9 or 12 by 12 inches, with smaller series closer and large types wider. It advises pinching at 8 to 12 inches tall by removing the top 3 to 4 inches. Seed company data fits: Johnny's Selected Seeds lists 9 to 12 inches and sowing in 72-cell flats four weeks before planting out (Johnny's Selected Seeds). Benary's technical guide for the cut flower series Oklahoma gives a spring crop time of 10 to 12 weeks from sowing and a plug crop time of 3 to 4 weeks (Benary technical guide).

Labor. Zinnia needs support netting, frequent harvest and, for pinched plants, an extra visit. Benary's guide says plants take about 3 to 4 weeks to branch and flower again after a harvest. Those are the handling steps to put in the labor score.

Decision. If the buyer wants mixed summer stems, zinnia scores well on bed weeks and cost. If the buyer wants early spring stems, it scores poorly because it cannot go out before frost has passed. Plan the planting schedule in the propagation guide.

Turn scores into a trial plan

Sources