Garden Talk: July 1, 2013

From NGA Editors

Awesome Asters

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Asters have long been favorites for the late-season garden. Their cheerful, star-shaped blossoms (the word ″aster″ is from the Greek for ″star″) in shades of white, purple, blue, pink, and red offer a lovely contrast to the yellows and golds of late blooming daisies, the muted tones of ornamental grasses, the glowing oranges, reds, and yellows of changing tree foliage, and the crisp, clear blue of the fall sky. Unfortunately, the beauty of the flowers can be marred by unsightly leaves affected with powdery mildew and rust, especially on the popular New England and New York asters.

To help gardeners choose the best-performing asters for their gardens, Richard Hawke, Plant Evaluation Manager at the Chicago Botanic Garden, recently released the results of a six-year evaluation of 119 different asters, comprising both native and non-native species and cultivars. Plants were grown in full sun and part sun trials at the USDA Hardiness Zone 5, AHS Heat Zone 5 garden and given minimal maintenance to duplicate common home garden conditions, with no insect or disease treatments or winter mulch. Plants were rated on a scale of one to five stars for cultural adaptability, disease and pest problems, winter hardiness, and their ornamental qualities associated with flowers, foliage, and plant habit. Although the goal of the evaluations was to identify asters best suited to the Upper Midwest, the results can be helpful to gardeners in other regions as well.

Here we need a brief aside about the scientific names of asters. Alas for gardeners, taxonomists have decided that the botanical generic name Aster is no longer accurate for our native species. Our North American asters now have a variety of new generic names, all uniformly daunting to pronounce and spell. For example, Aster novae-angliae is now Symphyotrichum novae-angliae; Aster divaricatus is now Eurybia divaricata; and Aster umbellatus now goes by Doellingeria umbellata. Whew! You may find these asters listed by their newer appellations in some catalogs and references, while others still retain the older names.

Seven asters received top billing. Those rating five stars included 'Jindai' Tatarian aster (Aster tataricus); white wood aster, both the species and its cultivar 'Eastern Star'(Eurybia divaricata); 'Snow Flurry' heath aster (Symphyotrichum ericoides); calico aster and its cultivar 'Lady in Black'(S. lateriflorum); and 'Raydon's Favorite' aromatic aster (S.oblongifolium). Nineteen other aster received a four-star rating.

To read A Comparative Study of Cultivated Asters and see rating of all asters in the study, go to Chicago Botanic Garden.

Begonia 'Sparks Will Fly'

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Garden impatiens has long been a favorite for adding color to shady spots in the annual garden. But a new disease threat, downy mildew of impatiens, has caused widespread devastation of this plant in many areas, many gardeners to look for some new choices adapted to low light conditions.

An eye-catching candidate is the new begonia 'Sparks Will Fly' (Begonia hybrida) from Burpee Home Gardens. Adapted to part to full shade and not susceptible to impatiens downy mildew, its vivid tangerine-colored flowers stand out above a mound of bronzy foliage from spring until frost. Reaching about 15-18 inches tall and 15-18 inches wide, it can be used in ground as an edging plant or in containers or hanging baskets. Fertilize monthly throughout the season to keep the plants thriving and pinch back any that start to become leggy. You'll get another visual treat when the flowers flush yellow in fall as the weather cools.

To read more about Begonia 'Sparks Will Fly', go to National Garden Bureau.

Math in the Garden

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We all know plants are amazing organisms, but did you know that some of them have done their math homework as well? Remember back in the dim reaches of high school math class learning about Fibonacci numbers, where each number the sequence is equal to the sum of the previous two? It turns out that many plants with spiraling shapes, such as cauliflower, artichokes, and sunflowers, make use of the Fibonacci sequence to pack their florets as tightly as possible, thereby maximizing the their ability to gather sunlight for photosynthesis. How does a plant accomplish this feat? It uses the hormone auxin to direct the growth of the florets in this most efficient spiral pattern. The way auxin and certain proteins interact within a sunflower, for example, gives rise to the astounding pattern of disk florets -- and later seeds -- in the center of the sunflower. In a recent study, researchers using a mathematical model to predict where auxin would accumulate in a sunflower were able to reproduce exactly the real Fibonacci spirals in sunflowers.

For more about this study, go to Science Shot. For more about Fibonacci numbers in the natural world, go to Fibonacci in Nature.

Bountiful Beans

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If you like to be up to the minute with your garden news, you'll be glad to learn that All-America Selections has just announced the first of its award winners for 2014! Vegetable Award Winner 'Mascotte' is a compact variety that will be welcomed by gardeners short on space or who grow veggies in containers. So whether you garden in the ground, in a pot on your deck, or even in a window box, you can enjoy a tasty harvest of long, crisp, slender pods that are held above the leaves for easy picking. 'Mascotte' shows high resistance to several troublesome bean diseases. Add to this its showy white flowers and you have a variety that will make an excellent addition to an edible landscape.

Like all bush beans, 'Mascotte' needs full sun and warm soil and weather. Plant seeds 2-3 inches apart in rows 12 inches apart. Pick beans regularly and the harvest will go on for weeks. Sow seeds every two weeks until midsummer for a continued harvest. 'Mascotte' matures in just 50 days, so in many parts of the country gardeners will still be get in one more planting this season that will mature before frost.

For more about 'Mascotte' bush beans and other AAS winners, go to AAS.

 
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