Tidewater Gardening - June 2009


Small Shrubs for Small Lots


K. Marc Teffeau

   The fourth Friday of the month is casual group lunch day in my office. We order out and have lunch delivered and take a longer lunch hour than usual to chat and chew. One of the ironies – and there are many – about working in downtown Washington, D.C., is that there are so many neat things to see, but you never have time to see them. Well, my office made an exception to that scenario in May when we moved our lunch date and had our casual lunch out at the National Arboretum. Some of the late flowering azaleas were in bloom, but between the timing and all the rain, the display had already peaked.
    Along with the trend away from the “McMansion” type homes on two acres is the move to smaller homes on smaller lots. As a result, there is an increase in demand for woody shrub and tree material that has a limited height, spread and grows more slowly.
    Dwarf evergreens can fill this landscaping niche and the best place to see a collection of these plants is the Gotelli Dwarf and Slow-Growing Conifer Collection at the U.S. National Arboretum. This seven-acre collection is by far the best display of dwarf plant material on the east coast.
    You can access a virtual tour of the collection at the National Arboretum Web site – www.usna.usda.gov – but you really need to see this display of evergreen plant material on site to appreciate the beauty, color and diversity that these shrubs and trees can bring to a small landscape.
    Generally, the definition of “dwarf” in the plant world includes plants that do not grow to the normal size of the species, or takes many years to do so. They are slow-growing and are generally about 1/20th the size of the normal species. Semi-dwarf plants may be 1/10th of the size.
    Usually most dwarf and semi-dwarf conifers will grow to a height of less than 6 feet in 10 years. Another interesting aspect of dwarfs and semi-dwarfs is that they may have different foliage and color than the parent. These plants can be used to provide year-round interest in the landscape, can be used by themselves or in front of taller plants, mixed with larger shrubs in shrub beds, serve as edging material or in raised beds. They can even be used as container plants.
    Most dwarf conifers prefer sunlight, but some do better in light shade. Their planting area needs to be well drained. If not you might consider raised beds to improve drainage.
    It is important that you know the required growing condition for the individual plant in question as some like microclimates protected from direct sun or the wind. Being evergreens, they will have a tendency to go off-color during the winter because of the cold temperatures and wind blowing over their needled foliage.
    Almost every genus of conifers has dwarf or slow-growing selections available. This is particularly true of species like the Norway spruce, pines, junipers, arborvitaes and false cypresses. There is even a dwarf selection of bald cypress, Toxidium distichum, ‘Peve Minaret,’ which is ideal for a small garden and turns a dusty red in fall.
    Many homeowners may be familiar with the dwarf Alberta spruce, Picea glauca albertiana ‘Conica,’ but there are a number of other dwarf firs like Abies balsamea ‘Hudsonia’ that work well in the landscape. A list of possible plants also include Tsuga canadensis ‘Pendula,’ Chamaecyparis lawsoniana ‘Minnima Aurea,’ Juniperus communis ‘Compressa,’ Juniperus squamata ‘Meyeri’ and Pinus mugo ‘Gnom.’
    Check with your local garden center to see what they may have in stock or could order for you. This is one of those times when it is worthwhile to do a little investigation before buying and planting. Check out the local library as they will have a number of excellent reference books on dwarf conifers.
    It is now time to divide and replant German iris in the perennial bed. Cut back the leaves and divide the clumps into single plants with one or two sections of healthy rhizome. Discard any diseased plants.
    If disease has been a problem with your iris, it may be wise to try a new location for them. Iris borer can be controlled with a systemic insecticide sprayed on the fans.
    If you haven’t done it yet, remove all old flower heads from rhododendrons and lilacs. These dead flower heads are best broken out by hand. Do this now to increase growth and the development of flower buds for next year.
    Weeds are the number one garden problem at this time of year. Mulching greatly aids in their control. Even if you haven’t mulched your plants yet, it’s not too late. First, clean up the bed of existing weeds. If you use a hoe, be sure not to cultivate too deeply around shallow-rooted plants. This is a good place to use a swan, scuffle or rocker hoe as they do not penetrate the soil deeply.
    Azaleas and boxwood are two shrubs that are especially vulnerable to careless cultivation. Do not mulch too deeply. Two inches is adequate in the landscape. Over-mulching is one of the main causes of plant death in the landscape.
    Roses have already reached their peak bloom. To make sure they continue to bloom all summer, keep to a regular watering schedule. Also, break off old blooms as soon as the petals drop off. Roses should be ready for a light application of 5-10-5 fertilizer, or an organic equivalent, now that their first blooming period is coming to an end.
    Grass clippings, weeds and other organic refuse will decompose rapidly in a compost pile during the warm summer months. To speed up the decomposition, shred the organic matter as fine as possible, add a thin layer of soil, lime and high nitrogen fertilizer, and keep the pile moist. Turn the pile every couple of weeks to help in the process.
    Many of the houseplants you placed outside for the summer will be making vigorous new growth now. Pinch and shape them as they grow to produce nice symmetrical full plants to bring back into the house next fall. Be sure to keep the insects under control so you don’t bring them back into the house too.
    Be on the lookout for the bagworm. This insect scourge of cedar trees and other narrow-leafed evergreens hatches out around the first of June. Each little “Christmas ornament” hanging on your cedar tree now contains between 200 and 1,000 eggs, ready to hatch when the temperature is right.
    Bagworms are best controlled as soon as they hatch, as the older and bigger they get, the harder they are to control with insecticides. The best “organic” control method is to hand pick and destroy the bags before the beginning of June.
    For the bags you can’t reach and remove, treat with an insecticide. Early in the hatch, spraying the plant with Bt or Bacillus thuringiensis is the best control. Sold under the trade names of Dipel, Bt or Biotrol, this naturally occurring bacterium is effective for caterpillars in the early stages of growth.
    Stop cutting asparagus in mid or late June when the spears become thin. After the last cutting is made, fertilize by broadcasting a 10-10-10 fertilizer at the rate of 2 lbs. per 100 sq. ft. Allow the tops to grow during the summer to store food in the crowns (roots) for the crop next spring.
    Start making successive plantings of green beans two weeks apart to provide for the entire growing season.
    It is still not too late to put in late vegetable transplants of tomatoes, peppers and eggplants.
    A last vegetable gardening hint: for very efficient, steady feeding of vegetables, sink a large can or bucket with many holes in its sides into the soil and fill it about 2/3 full of rotted manure or compost. Rain or occasional watering will keep a rich supply of nutrients seeping out to feed plants in a circle several feet wide. This is kind of like an organic liquid plant feeding.
    Happy Gardening!!