How to Sow

Cornflower seed should be sown directly in the garden after frost.

• Direct sow in average soil in full sun after danger of heavy frost.
• Select a location in full to part shade with good rich well-drained organic soil protected from wind.
• Prepare the bed by turning the soil under to a depth of 8 inches. Level with a rake to remove clumps of grass and stones.
• Most plants respond well to soils amended with organic matter. Compost is a wonderful form of organic matter with a good balance of nutrients and an ideal pH level, it can be added to your planting area at any time. If compost is not available, top dress the soil after planting with 1-2 inches of organic mulch, which will begin to breakdown into compost. After the growing season, a soil test will indicate what soil amendments are needed for the following season.
• Sow seeds evenly and cover with ½ inch of fine soil.
• Firm soil lightly, water and keep evenly moist.
• Seedlings will emerge in 7-10 days.
• Thin plants to stand 12 inches when seedlings are 1 inch high.

How to Grow

• Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating. 
• Mulches also help retain soil moisture and maintain even soil temperatures. For annuals an organic mulch of shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time. Always keep mulches off a plant’s stems to prevent possible rot.
• Keep soil evenly moist but not wet. Plants are drought tolerant, but watering during dry spells will improve flowering
• After plants are about 6 inches tall, a light fertilizer may be applied. Keep granular fertilizers away from the plant crown and foliage to avoid burn injury. Use low rates of a slow release fertilizer, as higher rates may encourage root rots.
• Taller varieties may require staking
• Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.
• Remove plants after they are killed by heavy frost in fall to avoid disease issues the following year.

Growing Tips

• Cornflowers are drought-tolerant and easy to grow. It is a great flower to introduce children to gardening. Deadhead cornflowers to keep them flowering.
• Cornflowers are perfect for cutting and drying, and they make a great addition to any cottage garden, wildflower meadow, or border. Dwarf cultivars are good for edgings and containers.
• Cornflowers are short season bloomers so to extend their flowering season plant a second crop two weeks later.

Common Disease Problems

Aster Yellows: Plants are stunted, develop witch's brooms (excessive growth), petals turn green and become deformed. This virus-like condition is spread by leafhoppers. Burpee Recommends: Remove infected plants and control leafhoppers. Remove weeds in the area which serve as alternate hosts to the disease.

Damping Off: This is one of the most common problems when starting plants from seed. The seedling emerges and appears healthy; then it suddenly wilts and dies for no obvious reason. Damping off is caused by a fungus that is active when there is abundant moisture and soils and air temperatures are above 68 degrees F. Typically, this indicates that the soil is too wet or contains high amounts of nitrogen fertilizer. Burpee Recommends: Keep seedlings moist but do not overwater; avoid over-fertilizing your seedlings; thin out seedlings to avoid overcrowding; make sure the plants are getting good air circulation; if you plant in containers, thoroughly wash them in soapy water and rinse in a ten per cent bleach solution after use.

Downy Mildew: This fungus causes whitish gray patches on the undersides and eventually both sides of the leaves. Burpee Recommends: Rotate crops. Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet.

Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.

Rust: A number of fungus diseases that causes rust colored spots on foliage and stalks. Burpee Recommends: Practice crop rotation. Remove infected plants. Contact your Cooperative Extension Service for fungicide recommendations.

Common Pest and Cultural Problems

Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Aphids are only a problem if the plants are stressed. Alyssum is used as a trap crop for lettuce. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.

Cutworms: These insects cut off the seedlings at the soil level. Burpee Recommends: Place a paper cup collar (use a coffee cup with the bottom cut out) around the base of the plant. They are usually mostly a problem with young seedlings. You can also control by handpicking and controlling weeds, where they lay their eggs.

Leafhoppers: Leafhoppers cause injury to leaves and stunt growth. They also spread disease. Burpee Recommends: Remove plant debris. Use insecticidal soaps. Consult your Cooperative Extension Service for other insecticide recommendations.

Spider Mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for miticide recommendations.

Stalk Borer: The larvae of this insect tunnel up and down inside the plant stem causing the plants to wilt. By the time the plant wilts it is too late to save it. The larva is 1.5 inches long, greyish brown with one dorsal stripe and two lateral stripes on each side. The lateral stripes on the front half are interrupted and the lower brown stripe extends forward onto the side of the head. The eggs hatch in May to early June, after the moth lays them the previous September or October. Burpee Recommends: Remove and destroy all plant debris and nearby weeds.

FAQ

Can I start cornflowers inside? Cornflowers are very easy to start outside and does not need to be started inside, however you can start them inside 4 weeks before you transplant them in the garden.

Can I use cornflowers as a cut flower? Yes, for fresh bouquets, cut newly opened blooms early in the morning and immediately set the stems in a jar of warm water. Later, strip the stems of lower leaves that might foul the water, and arrange the flowers in a vase with fresh water. Cornflowers will last up to a week or even longer if you add some floral preservative to the vase water. Cornflowers are also great for dried arrangements and floral crafts.

My cornflowers are tall, skinny with small flowers, what happened? Usually this is a result of overcrowding make sure they have enough room between plants.

Do cornflowers attract beneficial insects to my garden? Yes they attract bees and butterflies as well as other beneficial insects.

Are cornflowers edible? Yes the flowers have a clove-like flavor and may be used in teas, to decorate cheeses, cakes and rice dishes.