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Crop Tips: Chrysanthemums

Thursday, September 15, 2022 | Jose Chen Lopez

Chrysanthemums (Mums) may be the world’s most grown flowers. With over 200 varieties, they come in a wide variety of floral colors. There are three primary types of chrysanthemums: pot mums, cut mums and garden mums. They are adaptable to a wide range of climatic conditions, making them suitable to grow just about anywhere. Chrysanthemums are relatively easy to take care of, whether you grow them in the greenhouse or outside.

But there are cultural guidelines for the different varieties of chrysanthemums that need to be followed to ensure successful propagation and growing. Consult your plant supplier for detailed growing requirements of the varieties that you are planning to grow as their hardiness varies greatly depending on the cultivar. Remember that not all varieties require the same growing environment and some may be more ideal for your greenhouse environment or outdoor growing conditions than others.

Some points to consider:

Growing Medium

Chrysanthemums prefer a well-drained, well-aerated soilless medium with high water holding and cation exchange capacity. The growing medium should hold enough available water and nutrients to facilitate optimal plant growth during the heat of the summer months. Professionally produced growing media most commonly purchased for chrysanthemum production are ‘high porosity’ media, such as Premier Tech Horticulture’s PRO-MIX^® HP, PRO-MIX^® BRK and/or PRO-MIX^® BRK20.

These growing media are composed of sphagnum peat moss that will retain water and nutrients and professional grade perlite and/or composted bark that provide drainage and aeration to help reduce potential root disease problems. Mums grow best with a starting and growing-on media pH of 5.7 – 6.2.

Outdoor garden mums crop. Photo: Premier Tech.

Watering

In mums production, it is important to maintain moderate to high growing media moisture. Allow the growing media to cycle from moist to slightly dry. Avoid both excess dry downs and long periods of wet media, especially in poor weather conditions, as this increases potential for root disease.

To prevent water spotting or burning on sunny days, it is best to water earlier in the morning or later in the afternoon.

Fertilization / Nutrition

It is always recommended to have a comprehensive analysis of your water (alkalinity, EC, pH and potential nutrients) prior to beginning production. Water quality has a direct influence on the growing medium’s pH and availability of nutrients. It is recommended to choose a fertilizer that has between 60 – 75% of the total nitrogen in the nitrate form.

A fertilization program should consider some general nutritional guidelines, such as providing the correct amount of acidification or buffering to maintain proper growing medium pH, the correct nitrate-N formulation, the ideal balance of macro and micro nutrients for optimal plant growth and proper fertilizer application rate.

Most chrysanthemums are considered heavy feeders. If applying a water soluble fertilizer, they need a constant feed of 200 - 250 ppm nitrogen. If using a controlled release fertilizer, apply it at a conservative rate as hot weather increases the rate at which the fertilizer releases. Also use a product with a longer release as the summer heat will reduce the posted longevity of the product. Depending upon the variety, fertilization rates can be reduced when flower buds began to show color. The optimal media EC should be 1.5 to 2.0 mmhos/cm (2:1 extraction). Leach using clear water during production if EC is too high to prevent damage to root system and leaves.

Potential Problems

A number of pests attack chrysanthemums. Most notorious are leaf miners and thrips. Aphids, fungus gnats’ spider mites and whiteflies can also become a problem. Disease problems include Fusarium, Pythium, rhizoctonia and leaf and flower blights. These problems can be kept to minimum if basic cultural guidelines and practices are followed.

Controlling humidity levels, providing adequate air movement and the use of Premier Tech Horticulture’s PRO-MIX products with BIOFUNGICIDE* will help minimize any potential issues. Also avoid keeping the growing medium wet and allow it to dry between waterings will reduce root disease problem.

*All BIOFUNGICIDE™ products are available under BIOSTIMULANT in Canada and in Latin America.

This mum is being attacked by Pythium due to root damage caused by high salts from controlled release fertilizer. Photo Credit: Premier Tech.