Green Scene

In spring garden, weeds and faded blooms need attention

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By Joel M. Lerner
Saturday, April 10, 2010

With spring upon us, many plants have seized the opportunity to begin growing -- including many weeds. Flower blossoms opened quickly this year. The earliest to open are already in need of triage, and planting beds are begging to be cleaned up and weeded.

Weeds that are starting to sprout need attention. These germinated in fall and winter, including chickweed, speedwell, henbit, shepherd's purse and yellow rocket. They can be pulled by hand or with a weeding prong. One of the greatest banes to those who hate weeding is known as hairy bittercress (Cardamine hirsuta). This member of the mustard family grows everywhere in the world except Antarctica. It is self-pollinating, blooms throughout the year and loves moist soil. The weed is short-lived, having a life cycle of six weeks.

The most diabolical aspect of hairy bittercress is that by the time you realize there's a problem, damage control must happen immediately. The first flowers bloom in February and March, quickly forming seedpods that turn brown. If you touch one, it explodes, spraying seeds over about a three-foot area around each plant. If you're working near an infestation of bittercress, you can feel the seeds sprinkling onto your exposed skin. These seeds will sprout in days. As soon as new plants appear, begin pulling them and continue whenever you see them.

Plants considered weeds should be pulled as soon as seen. If you pluck several handfuls a day, they can be kept manageable. As has often been said by avid gardeners, weeds are plants growing where you do not want them. For example, I have seen acreage taken over by native hairy loosestrife (Lysimachia ciliata). It creates a handsome mass, growing 2 to 3 feet tall and wide with yellow flowers. Native obedient plant (Physostegia virginiana) displays beautiful pink flowers in summer. The best flowering is in full sun, but this plant is anything but obedient. It will cover large areas but might not maintain its upright spikes of "obedient" flowers.

Care for fading flowers

After daffodil and tulip flowers fade, cut stems that held flowers (called scapes) to the base. Let daffodil foliage season until it turns brown. Bulbs can be left in the ground to rebloom next year. Minor bulbs such as crocuses, hyacinthoides and scilla will season without cutting scapes. Tulips are best dug as their leaves yellow and brown. Lay them in the sun to dry for about two weeks, protected by chicken wire cages if wildlife is a problem. When the bulbs dry, knock off soil, separate the bulbs and place them in a porous bag with vermiculite to keep dry. Store them in a cool, dry location until replanting in November.

If perennials browned last fall and were not cut back, cut the stems now before new growth begins. Examples are liatris, verbenas, mums and black-eyed Susans. If liriope and perennial ornamental grasses have browned and died back, clip them to 4 to 6 inches. Use shears, a string trimmer or a lawn mower on its highest setting.

Some winter or early-spring flowering perennials such as leatherleaf sedges (Carex buchcananii) and evergreen sedges (C. pendula) shouldn't be cut back. They can be slow to renew or not renew at all. Don't prune bergenia, low mat-forming dianthus or winter-blooming hellebores, except selective pruning of browned leaves.

Prune forsythia, flowering quince and winter jasmine after blooming. Cut forsythia in half or to a height where it will not require pruning again until after it blooms next year. Flowers will form on this year's new growth. Flowering quince doesn't need pruning if it flowered well this year. When more wood than flowers show, cut it back to 18 inches. Winter jasmine only needs pruning when it has overtaken an area and is growing where you don't want it. It can be cut to 12 inches after flowering. It is an interesting ground cover year-round when planted over a wall or on hillsides. Renew only overgrown plants that have lost ornamental value.

Spring fertilizer

Fertilize deciduous shade trees only if you didn't fertilize them last fall. Use a general-purpose fertilizer that's not too high in nitrogen. (Formulations of 5-10-5 or 10-6-4 are good.) Be sure it doesn't contain weed killer. Use five to seven pounds per 100 square feet on the area under the tree's canopy. Follow label instructions. I prefer organic fertilizer with phosphorous derived from rock phosphate. If there isn't any rain, water the fertilizer in to help dissolve nutrients. And incorporate organic material into the root zones of plants. It helps tree roots retain moisture and increases soil's ability to hold nutrients. One inch of compost around the root system at tree base is the perfect complement to fertilizer. Don't pile compost against the bark.

There's no need to wait until summer to plant in containers, but annuals should not be planted until after the last frost date -- May 1 in the Washington area. Use perennials, trees and shrubs in pots, urns or basins, making sure the containers are large enough to accommodate several plants. A good guide is 30 inches in diameter and 16 inches deep for one woody plant (Japanese maples, false cypresses, junipers, or dwarf conifers) and three or four small perennials. Add annuals in May. Container plantings require watering, fertilization, pest control and good drainage.

Insects are waking up now, and disease-causing organisms that were dormant in winter are emerging. Spray dormant-oil insecticide or fungicide. Spraying now will ensure the least negative impact on the environment by reducing the need for additional spraying during the growing season.

If you don't want to use a petroleum-based product, make your own by mixing one cup of vegetable oil with two tablespoons of liquid dishwashing soap (not dishwasher detergent). Slowly add one gallon of water. Be sure to use a clean sprayer.

Thwart nibblers

Install low, inexpensive plastic or wire fencing around areas where rabbits like to dine. Eighteen to 24 inches is tall enough, and when leaves mature, rabbits stop eating them. Home remedies such as mothballs, dried blood, castor oil and cayenne pepper have limited success. They may need to be reapplied frequently.

Try protecting plants from deer with fences in the form of a wall, chain link or deer fence. The latter is rigid black plastic mesh eight feet tall that can be snaked around trees, through the woods, to be self-supporting. Other popular remedies include motion-sensor-activated water sprays, lights, sound, soap, hair and animal-based products using egg mixtures. These products are available at garden centers and home improvement stores or on the Internet.

Another method of deterring deer is to use plants that they don't eat. Some suggestions are viburnums, magnolias, thorny hollies, hellebores, rohdeas, foxgloves, irises, daffodils and catmints. Check with your Cooperative Extension Service, http://csrees.usda.gov/Extension/index.html, or your local garden center for a list of deer-resistant plants.

Prep hardware

Finally, the diligent gardener should clean, sharpen and oil shears, pruners and other cutting tools. Wash rakes, shovels and hand tools. Sand and oil any wooden handles with linseed oil mixed with just enough kerosene to thin the linseed oil so that it soaks into the handles. Get a head start on the season and you'll be ready for all your gardening chores.

Joel M. Lerner is president of Environmental Design in Capitol View Park. He may be contacted at info@gardenlerner.com.


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