Chrysanthemum: Indoor Sow Annual
How to Sow and Plant
Chrysanthemum may be grown from seed sown early indoors and transplanted outside after frost.
Sowing Seed Indoors:
- Sow chrysanthemum seeds indoors 8-10 weeks before last spring frost date using a seed starting kit
- Sow seeds thinly and barely press in. Do not cover with soil as light aids germination.
- 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.
- 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.
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.
- 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.
- Set plants 12 inches apart in the garden.
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.
- 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.
- Remove spent flower heads to keep plants flowering until fall.
- 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 frost in fall to avoid disease issues the following year.
- Chrysanthemums make great long lasting, fragrant cut flowers.
- Great for containers as well as in the garden as a bedding plant.
- Annual chrysanthemum blooms in late summer and fall. It is not hardy and is grown as an annual.
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.
Can chrysanthemum be used for cut flowers? Yes, cut the stems to the length you need and they make great cut flowers.
Do chrysanthemums attract pollinators? Yes, chrysanthemums attract butterflies.
Can I plant these in containers? Yes, the annual varieties tend to be small and good for containers. Be mindful that they will not bloom until late so combine them with something that blooms in summer, or move them to a more prominent location only later in the season.
Do I have to pinch chrysanthemums? Pinching mums when they are about 6 inches tall until early July can result in bushier plants with more blooms in fall.
Why aren’t my chrysanthemums blooming? Chrysanthemums do not bloom until the days begin to be shorter in late summer. They also will not bloom if they are not in full sun or have been fertilized too much with a high nitrogen fertilizer.