Premature budding or early flowering of garden mums could be a major headache for many growers. Last season, I received numerous phone calls and eMails in regard to plants finishing short or flowering too early. Both are a result of premature budding that occurs when plants initiate flower buds prematurely due to stressful weather and growing conditions before reaching reproductive stage.
Occasionally, only terminal buds will initiate too early and in most cases plants, will finish satisfactorily if kept moist and well fertilized. When all terminal and lateral flower buds initiate too early, plants will not always perform well unless flower buds are removed and plants are allowed to regrow under optimum conditions.
In most cases, low temperatures, short days and lack of adequate water and fertilizer in early stages are the main causes of premature budding.
Time & Location
Northern states will experience cold temperatures until the end of June (Figure 1), and several consecutive cool nights below 50°F will have greater influence on flowering than the day length. Small plants moved or planted outside too early and exposed to cold temperatures will flower prematurely and finish short. Crops planted too early in April or May will sometimes finish smaller than the ones planted in June grown under optimum weather conditions. In some cases, plants that budded too early had to be cut back and finished two to three weeks later than originally scheduled.
Garden mums are short-day plants, and some varieties will initiate flower buds with less than 10 ½ hours of darkness under black cloth conditions. A low light intensity in rooting areas combined with short days and lack of night interruption will cause premature budding in the South. The longest day in South Florida is only 13 ½ hours, and this is very close to what garden mums need for flower initiation.
Figure 1. Grand Rapids, Michigan–Monthly Climate Plot for June 2008. Source: NOAA’s National Weather Service
Growers can minimize premature budding related to cold temperatures and short days by maintaining adequate water and fertilization. At the same time, water stress and low fertility alone will reduce number of leaves and restrict branching and vegetative growth. Plants will appear hard and go into a reproductive mode before reaching proper size.
Similar problems may occur with high rates of a control-release fertilizer that could result in very high EC due to uncontrolled release in hot weather. High salts will damage roots and stop plant growth. If a control-release fertilizer releases in a very short time and all nutrients are leached with clear water, plants will later experience more stress from being underfed.
Premature Budding Prevention
In addition, any extreme weather conditions, like very high temperatures combined with low relative humidity or excessive rainfall causing root loss may result in premature budding.
Growers can often prevent premature budding by following these steps:
• Garden mums must never be allowed to dry during the early stages. Keep plants moist and well fed until they reach at least 60 percent of the final size.
• Avoid planting or moving plants outside too early if unable to ensure optimum temperature. Very cold nights will most likely trigger early flower initiation and plants will finish too short. The appearance of small flower buds will indicate the end of the vegetative growth.
• Feed with phosphor-rich fertilizer like 20-20-20 at 250 ppm right after transplanting to promote rooting and vegetative growth. Plants that are well fertilized will continue to develop lateral breaks and will be less likely to suffer from premature budding.
Duration of darkness in different states
on the 15th of each month in 2008 (Source: US Naval Observatory)
• Light cuttings in propagation: Four hours of night interruption from 10 p.m. to 2 a.m. will keep garden mums vegetative. Growers in the Deep South should light cuttings in propagation year-round.
• Use Florel only if necessary. Apply 500 ppm spray when cuttings are fully rooted or one week after transplanting. Florel will delay flowering in some varieties, so it is safer to use temperature and lights to prevent premature budding.
• Mist plants in the middle of the day for several days after transplanting or spacing outside during extreme hot weather. Misting will reduce heat stress and limit potential root loss.
• When using drip irrigation, consider half the rate of a control-release fertilizer in combination with liquid feed to minimize extreme EC fluctuations. This feed combo tends to keep plants more compact and well branched.
• GroLink varieties don’t require pinch to perform best under normal conditions unless terminal buds initiate too early and rooted cuttings have to be pinched. In such a case, use hard pinch by removing at least half an inch of top growth and leaving six to seven leaves. Plants will continue to branch and finish satisfactorily with minimum delay.
• Cuttings should be purchased from reliable suppliers that keep mother stock clean and vegetative at all times. The cutting quality and growing practices in early stages of the crop will surely determine if one has to deal with premature budding for the rest of the season. However, a proper variety selection, scheduling and attention to detail will be the key to producing reliable garden mums year after year.