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How to Maintain Healthy Roots in Outdoor Container Crops

By Ball Seed|August 14, 2025

With so many container crops in production this time of year, Dr. Josh Henry of Ball Seed Technical Services wanted to discuss keeping roots healthy when the weather is unpredictable. Field-grown container crops, including garden mums and fall container programs, are subject to fluctuating weather conditions such as temperature and precipitation extremes, making root zone management especially critical for these crops.

Excessive rainfall, nutrient leaching, and disease pressure can cause plant stress, poor growth, and crop losses. In particular, heavy summer rains are a major concern for growers, as they can leach nutrients and reduce the air-filled pore spaces, stressing the plants and making conditions more favorable for root rot pathogens to cause disease.

A proactive approach focused on maintaining healthy roots through disease prevention, irrigation, and fertility management is the key to success. Henry recommends the following three processes to implement:

1. Stay Ahead of Root Diseases

  • Wet, saturated conditions are conducive to root and crown rot pathogens, causing disease. Watch for low spots and improve field drainage.
  • Develop a comprehensive fungicide drench rotation covering major pathogens like Pythium, Phytophthora, and Fusarium. Utilize labeled fungicides, including strobilurins, thiophanate-methyl, and etridiazole.
  • Incorporate biological options that support root health. Some species of Trichoderma and Streptomyces are effective.

2. Manage Fertility with the Weather in Mind

Heavy rain can rapidly leach nutrients, leading to deficiencies. Fertilizing immediately after rain replaces low-EC rainwater with essential nutrients.

Consider a combination of controlled-release fertilizer (CRF) and water-soluble fertilizer (WSF) for consistent fertility. Incorporate a low to medium rate of CRF as a base to buffer against leaching and use WSF for quick corrections and flexibility.

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3. Avoid Irrigation Extremes

  • Water based on crop needs and weather, not based on a timer. Check moisture using the 1-5 scale or by weight and let pots dry slightly between waterings to promote deeper rooting. Aim for a 15% leaching fraction (LF).
  • Reduce irrigation after rain to prevent excess saturation, and consider the forecast to decide if watering is necessary.
  • Prioritize morning irrigations to reduce wet foliage and humid microclimates in the canopy.

For additional information on root zone management in outdoor container crops, please read the original article found on the Ball Seed website.

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Ball Seed is North America’s leading wholesale horticultural distributor. The Ball Seed team combines extensive experience, innovative thinking, and world-class customer service to ensure professional growers have the best products, most efficient tools, and dynamic growing solutions. See all author stories here.