Babcock: Spring best time to fertilize perennials

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Deb Babcock

Deb Babcock's gardening column appears Thursdays in Steamboat Today.

Find more gardening columns here.

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Choosing the right fertilizer for your plants can be tricky. Remember that some native wildflowers and some succulents, such as sedum, grow best when not fertilized.

— The gardening catalogs that we pour over this time of year often show the plants at their peak bloom, bursting with lush foliage and vibrant colors. To replicate that look once the plants are settled into your garden, you'll probably need to fertilize them.

Shopping in the gardening section of your favorite store can be daunting; there are so many fertilizer choices. Instead of guessing which one to buy, take a little time to learn the difference between organic and manmade fertilizers and dry, water-soluble and slow-release formulas. All are fine choices, but some might fit your needs better than others. Regardless of which you choose, always apply according to the label directions.

Chances are your perennials will get along just fine in your garden without any extra fertilization. However, they'll likely grow a little slower and not be as showy as the photos in the gardening books. Here's why:

Although plants in the wild live off the nutrients found naturally in the soil, Mother Nature limits the number of plants and the varieties that a particular amount of space can sustain. In our gardens, we tend to crowd in lots of plants with many differing requirements that all compete for the limited amount of nutrients already in the soil. To achieve vibrant growth, we need to help them out with additional nutrients in the form of fertilizer and/or organic compost.

Because perennials use up a huge amount of energy early in the spring as they begin another season of growth, now is a good time to give them a boost. For your plants that are grown for the flowers they produce, your fertilizer should have plenty of phosphorus, which is the middle number on the package (for example, 5-10-5). Nitrogen, the first number (5-10-5) is needed for foliage growth, and the third number, potassium, is needed for root growth and is especially helpful in the fall when plants store energy below ground, although it's not as necessary here, since our soil generally contains plenty of potassium. The three numbers refer to the percentage of each nutrient that is present in your package of fertilizer; the remaining percentages are mostly filler to help in application. A soil test will help you determine which nutrients, if any, are deficient in your soil.

Many gardeners tend to prefer organic fertilizers because manmade varieties tend to put a lot of salt into the soil over time. Because organic fertilizers release nutrients much slower than manmade ones, they might not give you as much foliage growth or flowers and should be applied again in mid-summer.

Some perennials do better without any fertilization. Native wildflowers such as Echinacea (coneflower), penstemon, and succulents such as sedum grow best when not fertilized.

If you work some compost or organic matter into the soil around your perennials at the start of each growing season, you'll also help the plant growth through slow-release nutrients as well as soil aeration and drainage.

Deb Babcock is a Master Gardener through the Colorado State University Cooperative Extension Service Office in Routt County. Questions? Call 879-0825 or e-mail gardeners@co.routt.co.us.

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