Best Practices for Growing Garden Mums
January 19, 2021 
Mum ‘Misty Lilac Pink’ (Ball Horticultural)
It may be winter, but it’s never too late, or too early, to review your growing practices for mum production to ensure that your 2021 mum crop is top-notch quality. Ball Seed’s “Keys to Producing Quality Garden Mums” resource is a good place to start for a refresh on best practices for growing fall garden mums. We’ve included a few of the tips here with Ball Seed’s permission.
Planting and Media
Planting is the most critical period in the production of a quality garden mum crop. Plant liners directly into the final container whenever possible. A lighter, well-drained media is preferred. A heavier media may delay rooting, reducing the quality of the finished crop. Avoid mixes that are too light and may dry out too rapidly.
Media starting pH in a soilless mix should be 5.8 to 6.4; a soil-based mix should be 6.0 to 6.5.
Thoroughly water liners before planting, with 300 to 400 ppm N from 20-10-20, to ensure that the liner is well fed, encouraging rapid establishment. Water immediately after planting with fertilizer, such as 20-10-20 at 300 to 400 ppm N, to charge the soil — so when roots emerge, strong growth will occur.
If outdoor temperatures are cool (50°F to 59°F), it is recommended that plants be started in a greenhouse with night temperatures maintained between 60°F to 69°F (16 to 21°C), with 65°F being ideal. This allows better take-off and initial growth, which is especially important when growing early flowering varieties. Low night temperatures at planting can promote premature flower initiation.
Garden mums should be grown in full sun; shaded areas can produce taller, weaker plants.
Pinching
Modern varieties do not require pinching in natural-season Fall crops. Pinching is suggested for black cloth, but many growers produce black cloth crops without pinching.
Spacing
A key to excellent quality is to space the plants once they start touching. Spacing plants too tightly promotes weak, stretched, poor-quality plants that are more likely to experience disease problems.
Irrigation and Fertilization
When irrigating, apply enough water to thoroughly wet the soil mass, allowing water to drip from the container. Never let the plant wilt during the early stages of production, as wilting can limit growth and reduce the overall plant size.
Mums are heavy feeders and require large amounts of nutrients during the early weeks of plant development. The majority of nutrients in the plant at flowering are in the plant at visible bud. Therefore, feeding early is critical for strong growth.
A program of regular soil testing is the best guide to determine the optimum fertilization regimen. High fertilization rates and low soil EC levels indicate that plants are taking up the nutrition. High EC levels indicate plants are not taking up the fertilizer — so reduce fertilizer rates.
Fertilizing immediately after planting is very important:
- Feed NH4 + P (20-10-20, 20-20-20) during early crop development (weeks 1-4). A rate of 250 to 350 ppm N will usually work well.
- After loading the plant early, you will want to avoid too much NH4 + P or stretched plants and soft growth will result. Use NO3 and reduced P (17-5-17, 15-4-15, 14-0-14, etc.) to tone the crop and reduce stretch.
- Once plants are at visible bud, slow the fertilizer uptake and monitor the EC to prevent salt damage to the roots.
Slow-release fertilizers, such as Osmocote, in combination with liquid feeds, may also be used. Avoid excess applications of slow-release fertilizers, since they can release rapidly under high temperatures and cause the EC to spike, which damages roots. Mums can benefit from a magnesium sulfate (Epsom salt) supplement. Once plants mature, fertilizer levels should be reduced to maintenance levels.
Premature Budding and Crown Bud Formation
Night temperatures above 68°F will delay flower initiation. As night temperatures exceed 75°F, flowering is inhibited. Several days or more of cool nights, less than 60°F, in late spring and early summer may trigger premature bud formation. This is not desirable and may cause the plants to finish too small.
If small buds are visible in the early stages of production, plants will most often still develop normally. This can be minimized by limiting stress, applying adequate fertilizer amounts (fertility levels should be high), and not allowing plants to wilt. Early applications of 500 ppm Florel one week after planting can help minimize premature bud set by helping to promote vegetative growth; this will not abort the existing buds.
Height Control and Growth Regulators
NOTE: Ball recommends an initial small-scale trial with all growth regulators.
B-Nine foliar spray applications control height and also produce darker, greener leaves and strong stems. Apply 2,500 to 5,000 ppm when breaks are 1 to 2 inches (3 to 5 cm) long to tone the plant and reduce stretch. A second application can be made two weeks later.
Remember that B-Nine application after visible bud will delay flowering. Weekly applications of B-Nine up to the time of breaking color will delay the flowering by one week. Once flower color is evident, B-Nine delay is minimum, but the application will enhance foliage. In greenhouse-forced summer crops, an application of B-Nine at 5,000 ppm can be applied 14 to 21 days after pinching to control the more vigorous varieties.
Bonzi drenches of 1 to 4 ppm can provide very effective growth control, but be sure to apply the correct volume to avoid stunting. Early-crop applications require less ppm than when applied later in the crop to get the same level of control. Bonzi can also be sprayed with rates ranging from 30 to 50 ppm. Florel can be used to promote branching, prevent premature budding, and delay flowering, and is best applied early in the crop cycle at a rate of 300 to 500 ppm. Effectiveness varies by variety.
More Mum Production Resources
Are you in the mood to learn more about producing quality mums? Check out these resources.
Garden Mum Culture Guide/Syngenta Flowers
Scroll down the page and click on the “Culture and Tech Library” box. Once there, search for mums in the Document Library Search and you will find a wealth of cultural information.
Garden Mums – 2020 Protection and Production Tips
Onfloriculture, a blog for Ontario greenhouse floriculture growers, includes some technical information for mum production from Ontario Ministry of Agriculture, Food, and Rural Affairs specialists Drs. Sarah Jandricic and Chevonne Dayboll on irrigation, fertilizer choices, pest issues, and more.
Growing Garden Mums for Fall Sales
Basic production tips from the University of Massachusetts for handling rooted cuttings, container production, scheduling, and fast-cropping mums for fall.
Garden Mum Disease, Insect, and Mite Control Options and Defense Against Fusarium Wilt in Chrysanthemum
Two excellent production articles found on the GGS Pro-Tech Tips blog.
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