Friday, June 20, 2008

Greenhouse and Nursery - Fertilizing Garden Mums

We have dozens of garden mum growers in Delaware and mums are a good fall item for garden centers. The following is information on fertizing garden mums for growers.

Many growers will be potting up garden mums and it’s a good time to revisit your fertilizer program. Mums are heavy feeders during the first few weeks. After flowers are formed, nutrient demand diminishes. Your fertilizer program and fertilizer selection should be based on irrigation water quality, so have your irrigation water tested if it hasn’t been done and conduct regular soil tests to monitor soil fertility.

There are several ways to fertilize mums. Some growers use 100% water soluble fertilizer through a drip system, some use 100% controlled-release fertilizer and some use a combination of water soluble and controlled-release. To start plants off right and prevent premature buds:
Use moistened soil when potting up plants, then water-in freshly planted cuttings with a fertilizer solution containing 200 to 300 ppm of 20-20-20 immediately after planting. The cuttings will establish faster and grow more rapidly.

Do not stress the young plants during their first 4 to 5 weeks of growth, especially during the first 10 days of the crop. Keep plants moist, well fertilized and properly spaced.
Check plant roots regularly to monitor plant health.

To encourage soft growth that branches freely, use 250-300 ppm 20-20-20 or a fertilizer that is at least 60% ammonical nitrogen as a constant feed during the first 2-3 weeks for all fertilizer programs. If using controlled-release fertilizer, keep in mind that its rate of release is affected by its formulation (rate of release), soil temperature and frequency of irrigation. Most formulations release at temperatures of 70°F or above, therefore during cold temperatures of late spring/early summer temperatures, fertilizer is going to be slow to release, when plants need the most fertilizer. This is why liquid feedings become important, to get plants moving and create vegetative growth. Liquid feeds of at least 60% ammonia forms of nitrogen, combined with no water stress, are important to minimize premature budding!

Examples of Fertilizer Programs for Garden Mums

1) 100% Water Soluble Fertilizer Using Drip Irrigation

After plants are established using 20-20-20 the first few weeks, switch to 200-250 ppm of 20-10-20 constant feed for 3-4 applications and then rotate to a calcium nitrate based fertilizer such as 15-0-15 for 1 application, then repeat. Once plants start to show color, reduce to 100 ppm constant feed.

2) Combination of Water Soluble Fertilizer and Low Rate of Controlled Release Fertilizer

Use 250 ppm of 20-20-20 at time of planting and constant feed for first two weeks then change to 20-10-20, 300 ppm once per week and use clear water from first color until sale.

Information from the June 5, 2008 edition of the New England Greenhouse Update.

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