Best Planting Time: Chrysanthemums should be planted as soon as weather and soil conditions permit. In general, we recommend waiting until all danger of frost has passed and the soil temperatures are increasing before planting into a garden. If growing in pots, the plants can be started a few weeks earlier than this and moved to a protected area at night or in the event of cold weather.
Soil Preparation: Chrysanthemums will grow in almost any soil type but good drainage is of the most importance. The addition of humis materials such as manure, compost, leaf mold, or peat moss is very beneficial. Superphosphate at the rate of 3 lbs. per 100 square feet is recommended but not essential. Gypsum or Dolomitic lime is also recommended at a rate of 10 lbs. per 100 square ft., especially if growing in highly acidic soil. If growing in pots, a well-draining potting soil consisting of peat and bark is recommended. Avoid anything listed as being for tropical plants and moisture control potting soils. Top soil can be incorporated to add weight and nutrient holding capacity at a 1:5 ratio.
Planting: Shallow planting, no deeper that the plant was in its rooting mixture is best but the plants can be planted deeper as well. We advise starting all plants in pots to begin with. Use nothing larger than a 6” pot for the initial planting. The plants will generally be ready for transplant in 2-3 weeks if using a 4” pot and 3-4 weeks if using a 6” pot. Transplanting to the garden or to a larger pot should be done as soon as good root development is seen around the pot. To check this gently remove the entire plant from the pot. Do not allow the plants to become root bound in the pots as this will slow growth at transplant. If transplanting to the garden space 12 inches apart in all directions for best results.
Cutting Back: If your plants are more than 10″ tall on July 1st, we recommend cutting back to 4″ or 6″, leaving some good green foliage or growth below the cut. The result will be shorter plants and better foliage at bloom time. On large flowered cultivars, select the most vigorous growth that results after the cut and make no further stops or pinches.
Pinching: When growth resumes after cutting back, removal of the very tip growing portion of the stem will promote more branching and flowers, and in some cases help determine bloom date. Large flowered types should not be pinched after July 5th. Small flowered types can be pinched up to Aug. 5th. An earlier pinch date will be necessary for September blooming types.
Lateral Removal: Large flowered types will only achieve their full potential of size and form if growth is restricted to a few stems, three to five at the most is best. After the stems you wish to keep are selected all other side laterals or branches should be removed as they occur. Remove them when they are short and soft as it is easier and so they do not rob the other stems and developing buds of growth.
Disbudding: Large flowered types will only reach their maximum size if flower buds are restricted one to a stem. For best results, remove all but the largest center bud in a terminal bud cluster when bud clusters are still very small. Terminal bud clusters will contain from 3 to as many as 5 buds. Crown buds which are the first to occur and are born singly, produce the earliest blooms.
Watering & Fertilizing: Chrysanthemums do not like to stay wet for long periods of time whether they are growing in pots or in the soil. Be sure to allow the soil to dry between being watered or applying fertilizer. It is best to not allow the plants to wilt but the plants will also tolerate some wilting as well. Be sure your plants need to be watered if they are wilting by checking the soil for moisture. If they are wilting and the soil is wet this could be a sign of a disease.
The regular use of a high Nitrogen and Potassium fertilizer will greatly increase flower size and numbers. If growing in the garden we recommend top dressing with a slow release fertilizer such as Osmocote 14-14-14 at planting time. Be careful to read the rates on the bags and note that slow release fertilizer varies depending upon temperature and humidity. A weekly feeding of a high analysis liquid fertilizer such as Miracle Gro can be beneficial after August 1st and until flower buds show color. Change to a 10-10-10 fertilizer, or no fertilizer, after this date.
If growing in pots two rules of thought can be used.
- Fertilize continually with a liquid fertilizer at a low rate of 100-200 PPM Nitrogen
- Fertilize every third time when irrigating using a higher rate of fertilizer, 300 PPM Nitrogen.
Do not fertilize if the plant are severely wilted in the pots. Plants should be flushed thoroughly with water on occasion so that salts do not build up in the bottom of the pots and burn the roots. To do this, irrigate the plants with clear water until water is dripping out of the pot(s) and allow them to sit for an hour. Irrigate again with clear water until water is dripping out of the pot(s).
Insects: Careful monitoring of your insect population is important. Chrysanthemums are susceptible to most common insects and mites with Aphids, Spider Mites, Thrips, Caterpillars, Leaf Miner and Plant Bugs being the most common. Infestations can rapidly develop from a few insects on a few plants to overwhelming numbers. Spot treatment of individual plants, particularly in the case of aphids, can often prevent spread to a general infestation. Lack of thoroughness in treating the underside of leaves is usually the reason for rapid re-infestation. Do not use the same type of insecticide more than three successive times or insects may become resistant. Soap and light oil spray are quite effective, but the target insect or mite must be contacted to be effective. Don’t use soap sprays on blooms or spray when temperatures are high.
Diseases: Diseases can be hard to specifically identify. Chrysanthemums are susceptible to many different root diseases. The best way to prevent disease is through proper care and irrigation of the plants. The most common diseases are Fusarium, Pythium, Rhizoctonia and Thielaviopsis. The most common symptom of disease is when the plants wilt, especially when the temperatures are high. Be sure your plants need to be watered if they are wilting by checking the soil for moisture. If they are wet and wilting it could be a sign of disease. Curative measures can be very expensive and generally involve the use of chemicals. There are many chemicals available, including some newer biological fungicides on the market.
Winter Care: Chrysanthemums on the whole are not entirely winter hardy in areas of hard freeze. In cold winter areas, dig up plants, prune back, and store in a protective area such as a cold frame, basement, or any area where they can be protected from freezing. If left in the ground mulch heavily with straw, decomposed manure or similar materials. In warmer areas, do not be hasty to cut back old stems until signs of new growth begin at base of plant.