The ABC's of Fertilizing Containers

March 31, 2011

Credit: All photos by Doreen G. Howard
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A continuous supply of nutrients and fertilizer is an absolute for lush container bouquets and productive edibles, I learned the hard way as a novice gardener.

My containers filled with petunias, salvia, lettuces and tomatoes looked awful, especially when compared to those I planted in the ground later. I was starving the container plants, because I didn’t replace nutrients that were leached out of the potting mix every time I watered.

Now I use this three-step fertilizer program, and my container gardens flourish.

A. Incorporate timed or slow-release fertilizer into potting mix when filling containers. (If the potting mix contains fertilizer, skip this step.) Fertilizer pellets are coated with a polymer that let them dissolve at varied rates; the thicker the coating, the long it takes for the fertilizer in pellets to be released into the potting mix. Most brands feed plants for at least 60 days, and some supply a steady stream of nutrients for up to 120 days. Check the label on any product you buy for this information.

Slow-release food is also available in organic form. Fish meal pellets are formulated similarly to synthetic fertilizers. Cotton seed meal, feather meal and alfalfa pellets are other slow-release organic choices. All feed plants for about 60 days. The alfalfa also contains a hormone, triacontanol, which promotes plant growth.

B. Apply water-soluble fertilizer every two weeks to supplement the slow-release fertilizer. Water-soluble ones deliver nutrients directly to plant roots and are easy to apply. Just dissolve them in water and pour the liquid into the container for a nutritional boost. Follow package directions for dilution rates and the amount of fertilizer to use on each container.

Organic choices such as fish meal emulsion and liquid kelp work well, too. In fact, some plants like ferns and lettuce respond better to organic products than to synthetic fertilizers.

C. If plants need a quick pick-me-up due to stress or heavy production of flowers or fruit, feed plant leaves directly. Deadhead old blooms, cut back damaged foliage and then spray water-soluble fertilizer on leaf tops and undersides. The spray delivers nutrients directly to where photosynthesis takes place. Results are dramatic—you’ll see growth or renewal almost overnight.

Use any spray bottle or garden sprayer and follow dilution rates given on the fertilizer package. A word of caution about foliar feeding. Don’t do it when temperatures are above 90ºF or when the sun is beating of plants directly. The fertilizer will burn leaves. The best time to foliar feed is in the morning or early evening.

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Doreen Howard has written for The Old Farmer's Almanac All-Seasons Garden Guide for 15 years and is the former garden editor at Woman’s Day as well as a photographer. She has grown more than 300 varieties of heirloom edibles and flowers in the last two decades.

In stores now!

Look for Doreen's newest book, Heirloom Flavor: Yesterday's Best-Tasting Vegetables, Fruits and Herbs for Today's Cook. Find in stores everywhere including Walmart and on the Web including amazon.com.

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