Garden Talk: September 27, 2007

From NGA Editors

Choose Among the Best Catmints

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Catmints are widely adapted, dependable, easy-care perennials. There are more than 20 species commonly available, and some flower better and have a more attractive growth habit than others. To determine the best varieties for home gardeners, the Chicago Botanic Garden grew 36 different catmints over an eight-year period -- from 1999 to 2006, evaluating them for ornamental traits, pest and disease resistance, hardiness, and adaptability to soil and environmental conditions. They were grown in full sun on well-drained soil with minimum maintenance. (Poor soil drainage is usually the downfall of catmints.)

The top catmints featured abundant lavender flowers from spring to fall without deadheading, and healthy green foliage. Four catmints received 5-star ratings -- the highest possible. ‘Joanna Reed’ grows 24 inches tall and 48 inches wide. ‘Six Hills Giant’ and ‘Walker’s Low’ grow 30 inches tall and 48 inches wide. ‘Select Blue’ is a low grower reaching only 14 inches tall and 30 inches wide. Eighteen other catmints received 4-star ratings and were deemed good choices for many gardens.

For more information on this study, go to Issue #29: A Comparative Study of Cultivated Catmints at: Chicago Botanic Garden.

Import Seeds With Ease

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Gardeners love to travel and invariably stumble across seeds of unique varieties when visiting other countries. Until recently you’ve needed a phytosanitary certificate to import seeds into the United States. However, the rules have now changed.

The USDA has instituted new procedures for importing "small lots" of seeds. Small lots are defined as less than 50 seeds each of up to 50 varieties. There’s no charge for importing these seeds. All you need to do is fill out the online permit that is valid for three years. The seed needs to be professionally collected with the appropriate information on the packet, such as the collector/shipper’s name, the country of origin, and the scientific name (at least the genus).

For more information on how to import small quantities of seed into the U.S., go to: Animal and Plant Health Inspection Service.

Evaluating Home Soil Test Kits

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Testing the soil is important for determining soil fertility and health. Whether it be for a lawn, flower garden, or vegetable garden, knowing your pH, nitrogen, phosphorous, potassium, and other nutrient levels will help determine what soil amendments you need to add before you plant. One of the quickest and easiest ways to test your soil is with commercially available home soil test kits.

Researchers at the University of California, Davis, tested five widely available soil test kits to determine their accuracy when compared with professional soil laboratory tests. They analyzed Salinas clay loam soil for the pH, nitrogen, phosphorous, and potassium levels using the home test kits and the professional soil laboratory results.

Researchers found the LaMotte Soil Test Kit and Rapitest kits performed the best, with at least 90 percent accuracy in these categories. Some kits were more accurate with certain nutrients. For example, nitrogen levels were most accurately determined by Rapitest and Quick Soiltest, phosphorous levels by Rapitest, and pH by LaMotte Soil Test Kit. Potassium was determined with equal accuracy by all kits except the Soil Kit.

For more information about this soil test kit research, go to: Hort Technology.

Wash Tree Roots Before Planting

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Fall is a great time of year for planting deciduous trees around the country. If you’re planting large balled and burlapped trees, you know there is as much work involved moving the tree to the hole as there is in planting it. Now new research from Virginia Polytechnic Institute may help make planting large trees easier and more successful.

For years home gardeners have been told to keep the rootball intact when planting to ensure the most success. But researchers in Virginia have experimented with a technique first tried by the Community Forestry Consultants in Spokane, Washington. Before planting they washed the soil off the rootball to create a bare-root plant. It seems there are several advantages to root washing. It exposes the root system so you can prune any circling or damaged roots. Root washing allows you to more easily locate the root crown, and makes the tree easier to handle and plant at the proper depth.

Continuing this experiment, researchers at Virginia Tech wanted to find out if root washing had any negative impacts on the tree's future growth. So they washed the roots of one-quarter of the 3-1/2- to 4-inch-caliper red maple trees. One-quarter of the remaining trees were planted with the rootball intact, one-quarter had the soil removed by air blasting, and one-quarter were dropped 10 feet (to simulate removal from a truck), which caused some of the soil to fall off the roots. Researchers planted a group of these trees in March and another group in July in the 95-degree heat. By October, to their surprise, all the trees, regardless of the treatment, were deemed healthy and had similar growth rates. They plan on continuing the trials next year.

For a copy of the May 15, 2007, issue of American Nurseryman magazine with the article “The Bare Root of the Matter" about this research, go to: American Nurseryman Magazine.

 
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