Learn About Chrysanthemums

How to Sow

Chrysanthemum may be grown from seed sown early indoors and transplanted outside after frost, or sown directly in the garden in summer, or grown from potted plants.

Sowing Seed Indoors:

  • Sow chrysanthemum seeds indoors 2 months  before last spring frost date using a seed starting kit
  • Cover the seeds lightly with 1/8 inch of seed starting mix
  • Keep the soil moist at 70-75 degrees F
  • Seedlings emerge in 10-21 days
  • As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
  • Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
  • If you are growing in small cells, you may need to transplant the seedlings to 3 or 4 inch pots when seedlings have at least 2 pairs of true leaves before transplanting to the garden so they have enough room to develop strong roots
  • Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning.  This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.

Sowing Directly in the Garden:

  • Direct sow after all danger of frost.
  • Remove weeds and work organic matter into the top 6-8 inches of soil; then level and smooth. 
  • Sow seeds evenly and cover with 1/8 inches of fine soil. 
  • Firm the soil lightly and keep it evenly moist. 
  • Seedlings will emerge in 10-21 days.

Planting in the Garden:

  • Select a location in full sun with good rich moist organic soil.
  • Prepare the bed by turning the soil under to a depth of 6-12, inches removing any debris, and lightly raking as level as possible.
  • The addition of organic matter (leaf mold, compost, well-rotted manure) benefits all gardens and is essential in recently constructed neighborhoods.
  • Plant on a cloudy day or in late afternoon to reduce transplant shock.
  • Dig a hole for each plant large enough to amply accommodate the root ball.
  • Unpot the plant and gently loosen the root ball with your hands to encourage good root growth.
  • Place the top of the root ball even with the level of the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand.
  • Use the plant tag as a location marker.
  • Thoroughly water and apply a light mulch layer on top of the soil (1-2 inches) to conserve water and reduce weeds.

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 germination. 
  • Mulches also help retain soil moisture and maintain even soil temperatures. For perennials, an organic mulch of aged bark or 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.
  • Careful watering is essential in getting perennials off to a good start. Water thoroughly at least once a week to help new roots grow down deeply. Soil should be damp at about 1 inch below the soil surface. You can check this by sticking your finger in the soil. Water early in the morning to give all leaves enough time to dry.  One inch of rain or watering per week is recommended for most perennial plants. You can check to see if you need to add water by using a rain gauge.
  • Until plants become established, some protection from extreme winds and direct, hot sunlight may be necessary.  Good air movement is also important.
  • After new growth appears, 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.
  • Chrysanthemums may benefit from being pinched up until the Fourth of July. This should make plants bushier and will not prevent blooming as chrysanthemums bloom when the days begin to grow shorter, in fall.
  • “Deadhead”, remove spent flower heads to encourage continuous flowering and prevent seed development.
  • Remove and discard foliage after a hard frost in fall. 
  • In colder regions, apply another layer of mulch (1-2 inches) after the ground freezes in fall. Evergreen boughs (from Christmas trees) provide additional protection. Remove this mulch in the spring.
  • Divide perennials when plants become overcrowded, bloom size begins to diminish or plants lose their vigor. Divide chrysanthemums in spring, just as they begin to grow. Dig clumps from the ground and with a sharp knife or spade, cut into good sized divisions, each with several growing eyes and plenty of roots. Remove any dead or unhealthy plant parts and cut back stems. Replant one division where the plant was originally and plant the extra divisions elsewhere in your garden or give them away to gardening friends. Plant the divisions immediately, or as soon as possible, and water well.
  • Chrysanthemums may also be propagated from cuttings taken in spring.

Growing tips

  • Many gardeners do not cut back perennial flower seed heads in the fall, but wait until early spring before the new foliage appears. This provides food for wildlife over the winter.
  • Chrysanthemums make great long lasting, fragrant cut flowers.

Common Pests and Problems

Common Disease Problems

Alternaria Leaf Spot: Small, round reddish brown spots with white to gray centers form on the upper surface of the leaves. The lesions may encircle the stems and cause wilt. This disease is worse in warm, wet or very humid weather. Burpee Recommends: Avoid getting water on the foliage. Remove infected plant parts and do not work around wet plants. Provide plenty of air circulation. Contact your Cooperative Extension Service for fungicide recommendations.

Botrytis: This fungus causes a grey mold on flowers, leaves, stems and buds. It thrives in cool wet weather conditions. Burpee Recommends: Remove affected plant parts, avoid watering at night and getting water on the plant when watering. Make sure plants have good air circulation. Contact your Cooperative Extension Service for fungicide recommendations.

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.

Root Rots: A number of pathogens cause root rots of seedlings as well as mature roots. Burpee Recommends: Pull up and discard infected plants. Make sure your soil has excellent drainage. Contact your Cooperative Extension Service for recommendations.

Rust, Brown: Dark brown masses of spores form in pustules on both leaf surfaces. Burpee Recommends: Remove infected leaves and discard into the trash.

Verticillium wilt: First seen on leaves in late spring after fruit production has begun. Leaves turn brown along margins and between veins. Leaves will wilt and dry up as the disease progresses. Burpee Recommends: Remove infected plants. Do not plant in areas of infection.

Common Pest and Cultural Problems

Aphids: Greenish, red, black or peach colored sucking insects that can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. 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.

Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage.

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.

Thrips: Thrips are tiny needle-thin insects that are black or straw colored. They suck the juices of plants and attack flower petals, leaves and stems. The plant will have a stippling, discolored flecking or silvering of the leaf surface. Thrips can spread many diseases from plant to plant. Burpee Recommends: Many thrips may be repelled by sheets of aluminum foil spread between rows of plants. Remove weeds from the bed and remove debris from the bed after frost. Check with your Cooperative Extension Service for pest controls.

Wireworms: These insects live in the soil and kill seedlings by girdling their stems at the soil line, bore into stems, roots and tubers. They may be found around the stems in the soil are and ¼ to ¾ inch long, thin, yellow brown worms with a shiny skin. The adults are called click beetles, and are about 1/3 inch long, reddish brown with a hard shell. Burpee Recommends: Rotate crops. Check with your Cooperative Extension Service for pesticide recommendations which must be applied prior to planting. 

FAQ

When is the best time to plant mums? In the spring, either sow indoors two months prior to the last frost, or plant after last frost.

Can mums be used for cut flowers? Yes, cut the stems to the length you need and they make great cut flowers.

Are the mums you see for sale in farmer’s markets in fall good for the garden? The mums you see for sale in the fall are mostly used for fall decorations and are not likely to be hardy in the garden.

Do mums attract pollinators? Chrysanthemums attract butterflies.

When will my mums bloom? Mums will bloom from August to the first frost. They are day length sensitive plants that will only bloom when the days begin to grow shorter.

 

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