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How to keep the blooms going!

Poorly-fertilized hot pepper. Tomatoes (background) are well-fertilized.
Photo: Anne Sawyer

Now that summer is in full swing, you’ll likely need to fertilize container plants to maintain optimum growth...and keep those blooms going!

If you used a pre-fertilized commercial potting media, you won’t need to fertilize for the first two to three weeks after planting.

If a controlled-release fertilizer was mixed in at planting, you may not need to fertilize for eight to ten weeks. Once that time has passed, however, you may start to notice slowed growth, yellowing of foliage, or other signs of plant decline if you haven’t applied additional fertilizer.

Why fertilize now?

Nutrients in containers decline quickly as a result of rapid plant growth and frequent watering, which can leach nutrients from the potting media.

What kind of fertilizer should I use?

There are many fertilizer options for container plants:

  • Liquidor soluble fertilizers, for example, are easy to apply during routine watering and may be applied every week or two at full strength or more frequently if diluted. 
  • Inorganic soluble fertilizers are best for rapid delivery of nutrients to plant roots. If using organic fertilizers such as fish emulsion or kelp extract, be aware that nutrients may not be available quickly enough for fast growing plants, although organic fertilizers are often a great source of micronutrients such as iron or manganese. 
  • Controlled-release fertilizers are an excellent option for container plants. They can minimize nutrient losses through leaching and provide plant nutrients for several weeks to months: duration depends on plant growth, watering frequency, and temperature (warmer temperatures can release nutrients more quickly).

Dangers of over-fertilizing

Regardless of which fertilizer you choose, always follow label instructions for application! Over-fertilizing is detrimental not only to your plants, but also to your wallet and to the environment.

Author: Anne Sawyer - Extension Educator, On-Farm Food Safety in Horticulture

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