Garden Talk: September 29, 2005

From NGA Editors

Five Steps to Bulb Planting Success

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The best time to plant spring bulbs depends on where you live. Ideally, wait until the soil temperature is below 60°F. As a general guide, plant in September through early October if you live in USDA Hardiness Zones 4 or 5; October to early November in zones 6 or 7; and November to early December in zones 8 and 9. Plant bulbs that have been refrigerated for 8 to 10 weeks in late December to early January in zone 10.

To discourage voles or gophers, add a handful of sharp gravel to the planting hole or plant bulbs in wire or fabric baskets. Don't mulch where rodents are a problem.

Layer two different species, such as tulips and grape hyacinths, in the same bed for exciting color combinations. Plant tulips first, then add enough soil to achieve the proper depth for the grape hyacinths. Plant the grape hyacinths between the tulips.

Set the bulbs in a planting bed or in separate planting holes with their roots or basal plate downward. If you are unsure which part of the bulb is the bottom, plant the bulb on its side.

Plant a variety of bulbs to extend the flowering season. In addition to daffodils and tulips, include some early-flowering bulbs, such as crocuses, snowdrops, and scilla, to herald the start of spring. Late-flowering alliums will continue the show into early summer.

Fall Cleanup Q and A

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Cutting Back Perennials
Question: After the first frost, should I cut back the flower stalks on my perennials? Or is it best to leave them as is and cut them back in the spring?
Answer: If winter temperatures in your region are regularly below 0 degrees F, don't cut back the perennials until late winter or early spring. The dead foliage helps protect the plants from cold. After the ground freezes, cover the whole bed with a loose layer of straw. Leave it until early spring and then gradually remove it as temperatures warm.

Pruning Ornamental Grasses
Question: What is the proper method of cutting back ornamental grasses for the winter?
Answer: Most gardeners wait until after the grasses have bloomed so that they can enjoy the ornamental plumes. The seedheads are also attractive in winter, so you may want to wait until spring to trim them. Then, cut the dead grasses back to about 6 inches; the new growth will quickly cover the old stubs. Some gardeners use a hedge trimmer, as this is much faster than using a hand clipper.

Composting Leaves
Question: I would like to make a 4x4x4 fenced-in area and compost fall leaves. If I fill the bin in early November, will the leaves decay by the middle of May, when I can rototill them into the soil?

Answer: Composting essentially stops when the weather turns cold, and plain fallen leaves alone can take a year or more to decompose. To speed up the process, shred the leaves with your lawn mower, then till them into the soil this fall. By spring they should be decayed enough for planting.

Plant Protector Bags

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With fall around the corner, thoughts turn to protecting prized plants from frost. Many gardeners watch the forecast for threats of frost and then run out to protect plants with blankets, buckets, and plastic tarps. A new product makes it easier to protect warm-season annuals -- such as peppers, basil, and potted plants -- not only from frost but also from high winds and damaging rain.

Plant Protector Bags are made from a spun-bonded polypropylene material, and they protect plants down to 27°F. They allow air, light, and water in, yet they don’t stunt plant growth. The bags come in two sizes: 40" x 45" and 50" x 55". To use, simply pull the bag over the plant and tug the drawstring to shut the open end around the base of the plant. They are best left on for only 24 hours at a time.

For more information on the Plant Protector Bags, go to: Easy Gardener.

Shrub Dogwood Trials

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Shrub forms of dogwood (Cornus) make excellent landscape plants and are widely used by landscapers around the country. They are known for their green or variegated foliage, attractive flowers and fruits, fall foliage color, and colorful stems in winter. However, with so many dogwood varieties available, it's often difficult for homeowners to choose the best one.

Since 1999 Longwood Gardens in Kennett Square, Pennsylvania, has been evaluating 33 different types of shrub dogwoods for plant habit, size, foliage, flowering, fruiting, and pest resistance at their USDA zone 6 public garden. They have rated each species on a scale of 1 to 5 for each characteristic. Here are the top-scoring dogwoods by category.

The top-ranked species dogwood was Cornus sericea var. coloradensis. This North American native had better leaf, stem, and fruiting than other species and a more symmetrical, round habit.

The top variegated-leaf dogwood was Cornus alba 'Argenteomarginata'. This cultivar has beautiful green and white variegated leaves with a tinge of rose coloring in summer. It was especially resistant to disease.

The best yellow-twigged dogwood was Cornus alba 'Bud's Yellow'. It has exceptional stem color from a distance. The best red-stemmed dogwood was Cornus sericea 'Baileyi'. It stood out for its bright stems and nice plant form.

For more information on these dogwood trials, contact: Longwood Gardens.

 
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