Seed Starting

Cosmos is a heat-loving plant and does best above 60°F. Below 55°F, growth and flowering are inhibited.

To direct seed: after last frost, once soil temperature is above 60°F, sow seed thinly in rows, barely covering the seeds (planting seeds too deeply will hinder germination). Keep soil consistently moist until seeds have germinated. Seeds will germinate in 7–10 days at a soil temperature of 68–72°F. Thin to 9–12” apart when the first true leaves appear.

To transplant: sow seed thinly in flats, barely covering the seeds, 5–7 weeks before setting out. Keep soil at 68–72°F  and consistently moist until emergence. When the first true leaves appear, transplant into larger cell trays or containers. Harden off and transplant outdoors after the last frost, 9–12" apart. Wider spacing creates stronger, thicker stems. Planting in IRT (Infrared Transmitting) or black plastic mulch will aid in weed suppression and warming of soil.

To encourage longer lateral stems, some growers pinch out the central bud, also called growing tip, of young plants. As long as seedlings have developed several sets of true leaves, this can be done at the mature seedling stage, a few days before transplanting out in the field or garden. It is also possible to wait until plants reach 18” in height, then trim them with hedge shears to 10–12” tall.  Pruning or pinching the plants in this way improves the branching habit and results in longer, more numerous and uniform lateral branching and an easier harvest. Plants that are not pinched or pruned tend to direct resources to the central growing point/stem rather than the lateral branches and can grow excessively tall, sometimes resulting in few harvestable blooms and plant lodging.

For a continued harvest, pinch (deadhead) expired blooms.

Zinnias perform best in direct sun in well fertile, well drained soil full of organic matter. 

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Transplant (recommended) - Sow into 72-cell flats or preferred seedling container 4 weeks before planting out. Cover seeds. A heat mat will help maintain an accurate temperature. Lower temperatures will result in slower germination: 5-7 days at 70-75°F. Do not allow plants to become root bound and avoid disturbing roots; transplant shock or other stress events may cause double-flowering varieties to produce single blooms for a period following stress.

Direct seed - Sow 1/4" deep.

To encourage new blooms throughout the season, sow/plant every 2 weeks for prolonged yields of high-quality stems.

Pinching of initial bud or bloom and subsequent deadheading is recommended to encourage strong branching and bloom production.

Very sensitive to frost.

First-year flowering perennial.

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Elegant 2½–3½" blooms with long, clean, wiry stems and good vase life. Perfect for cutting. Seed pods can be used to add whimsy and interest to mixed bouquets. Produces all summer long. Also known as sweet scabious, Caucasian pincushion flower, and perennial Scabiosa. Perennial in Zones 3–7.

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Transplant (recommended) - Sow 6-8 weeks before planting out. Barely cover seeds as light is required for germination. Transplant to cell packs when the first true leaves appear. In the greenhouse, grow transplants at 60-65°F. Lower temperatures can cause premature flowers and poor garden performance. Harden off and transplant outside after the last frost.

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Direct seed (recommended): In early spring after last frost (sow in the fall in the South). Sow seed thinly in rows, covering lightly. Make 2-3 successive sowings, 2 weeks apart for a continuous summer harvest.

Transplant:  Sow 4-6 weeks before planting out. When first true leaves appear, transplant into larger containers. Harden off and transplant outdoors after last frost. Tips: chill seed at 40-45°F(5-8°C) for 1-2 weeks prior to sowing in the greenhouse. Cooler temperatures of 58-62°F(14-17°C) are best for seedling establishment. Support may be needed if grown in windy areas.

Transplant: Sow in pots 6-8 weeks before last frost, cover lightly with vermiculite or a humidity dome and keep at 65-70°F until germination, then at 50-60°F. Be very gentle when transplanting, as poppies do not like to be disturbed.

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Direct Seed: Direct sow in early spring or late fall or winter sow to provide a natural chilling period for the seed for the best germination.

Direct seed (recommended): After danger of frost, sow at a depth of 1/4". Make 2-3 successive sowings 2-3 weeks apart for continuous blooms from summer to heavy frost.

Transplant: Sow 4-5 weeks before planting out.

Transplant (recommended): Sow 1/8" deep into 72-cell flats or preferred seedling container 6-8 weeks before planting out. Heat and reduced daylength initiate flowering. Establish plantings early to avoid short stems.

Direct seed: Once soil temperature is 65-70°F. Provide support. Row cover or insect netting helps prevent the spread of Aster Yellows Virus by leafhoppers. Pinching not required.

Transplant: Sow 3-4 weeks before last frost. Transplant out after last frost.

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Direct seed: Sow as soon as soil can be worked. Cover seeds lightly with soil as darkness is required for germination.

Direct seed (recommended): Plant seeds 1/4" deep, 2-3 seeds per inch, in rows 18" apart. Firm the soil over the seeds. Thinning is not necessary, but a final spacing of 4-8" apart produces healthy, full plants. 

Transplant: Sow indoors 6 weeks prior to setting out. Plant 1/4" deep and keep at 70°F (21°C) for best germination. Transplant to the field when seedlings have 3-4 sets of leaves.

Transplant (recommended): Sow into 50-cell flats or preferred seedling container 5-6 weeks before planting out. Light aids germination; cover just enough to hold seeds in place. Harden off plants and transplant out after danger of frost.

Direct seeding is not recommended.

Transplant: Sow into 72-cell flats or preferred seedling container 6-8 weeks before planting outside. Cover lightly with 1/8" growing media. Harden off plants and transplant out after danger of frost.

Direct seeding is not recommended.

Transplant: Start indoors 3-4 weeks before transplanting out after last frost, or sow seeds in place after frost. Cover lightly in fine, moist soil, and keep warm until germination. Grow plants in full sun.

Transplant: Sow into 128- or 72-cell plug flats or preferred seedling container 5-8 weeks before planting out. 128-cell plugs require 5-7 weeks, and 72-cell plugs require 6-8 weeks of growing to mature transplant. Harden off seedlings before transplanting out.

Direct seed: Sow into cool soil for best results. Cover seeds with 1/4" soil. Thin as needed once true leaves appear.