With July's oppressive heat and humidity, most gardening homeowners take a well-deserved vacation from the garden. After all, the lawn barely needs cutting every week and the rightful decision has been made to leave the clippings behind to enrich the humus content of the lawn surface. Shrubs and trees appear to be holding their own, albeit without problems. On the whole, this is an easy month by garden standards, but still there are problems without apparent solutions.
Consider the demise of the rose garden. Once upon a time, it was the showplace of the landscape. Seldom did a week pass that the hybrid tea roses were not pampered and fussed over. Routine inspections allowed you to stay on top of things. Problems really never got you down, but the schedule did.
The next year, interest in the rose garden ebbed and plants suffered. Neighboring trees began to cast lengthening shadows over the roses, soon preventing veteran roses from ever flowering again.
Today, so much of the rose garden is in shade that only severe pruning of overhead trees would allow roses to flower once more. In such cases, cosmetic pruning could be undertaken now, with major surgery postponed to early March of next year.
Then, there is the black spot disease that now afflicts every rosebush. Some have made no effort to control the problem, in which case the disease is so widespread that only near-total surgery will rectify things. If you were to hand pick all tainted and spotted leaves, the plant could well be devoid of foliage.
Here are some corrective measures to consider for troubled roses:
Poor Growth. Soak the plants first, fertilize, then water again. Since the rose season is a brief one, no fertilizer should be applied after mid-August so plants terminate growth early in September. The July choice for fertilizer is plain-and-simple fish emulsion, but apply an inorganic product (Peters's 20-20-20, MiracleGro, Ra-Pid-Gro) in mid-August. Another stimulus is magnesium sulfate, commonly called Epsom salts. Stir a tablespoon into a gallon of water, then apply to the soil for each rosebush. One application now and another in August will work miracles.
Black spot. From spring through early July, make weekly sprays of Ortho Funginex (generic name is Triforine) to all roses, preferably in the evening when no rain is forecast. Thorough sprays with Funginex will keep your roses free of disease. If any leaves become spotted, pick the leaves promptly to prevent infecting other foliage; also, check the mulch or soil weekly for fallen leaves. Summer black spot is controlled with Funginex, but you should alternate this with Rubigan from here on to promptly stop powdery mildew. Discontinue Rubigan the last week of September, but continue with Funginex to mid-October. Make every effort to stop diseased leaves from overwintering in the garden.
Insects. Weekly plant checks will indicate whether routine sprays are needed or not. Diazinon sprayed to roses every 10 days (at night, of course) will halt most pests, but new products on the market (Avid, Pentac, Tempo II) offer outstanding control of all insects, including thrips. By joining the Potomac Rose Society, you will have access to these and other solutions for serious rose maladies. If you're deluged with Japanese beetles, buy traps at the garden shop and mount them quickly; the only other option is every-other-day spraying of Sevin to flowering roses.
Watering. Overhead watering is out. Instead, put down some soaker hoses, snaking them around your roses and covering the hose with mulch. Twice-a-week soaking of roses this way will turn plants around quickly.
Next, if you accepted our challenge of two weeks ago to propagate cuttings from azaleas and other shrubs, your next inspection of the cuttings will verify that they have taken root and can be transplanted. Don't move any cuttings without checking each to verify the presence of roots.
Opt for three- or four-inch plastic pots, one per cutting. Pre-mix your 1-1-1 soil formula (equal amounts of milled or compressed sphagnum peat moss, perlite and vermiculite) in a paper bag, dumping the contents into a plastic dishpan of hot water to wet your materials down. Once moist, spoon the soil onto sheets of newspaper atop the kitchen counter to surface dry for a few minutes, then spoon into the pots. Since the pH is less than 4, add a teaspoon of lime to each pot, forking it into the soil.
Scoop out just enough soil in the middle of the pot to accept the rooted cutting. Move the cutting to the small plastic pot with a plastic spoon, working soil around the cutting afterward. Flush out the air pockets with an immediate application of warm water while the pot drains in the sink. Label each pot at this point to identify the cutting.
Move all the pots onto cookie sheets to eliminate the need for saucers. Move the plants into a room with bright indirect light, but no direct sun on the plants. Average room temperatures in the 80s are well suited for the plants.
Once transplanted, the cuttings will require lightly moist soil at all times; this usually translates to wetting the soil every other day. Alternate waterings with weak applications of fertilizer, perhaps fish emulsion if you have it, otherwise liquid 5-10-5 at one-third the rate suggested on the label. Rotate pots a half-turn whenever you wet the soil. Plants will be transplanted to six-inch pots in early September and moved outdoors prior to a final transplant to the garden the last days of September.
Other weekend chores:
Inspect trees for crown gall, a black, tumor-like growth most often found on twiggy branches, but sometimes on tree trunks just above the soil line. Most often, galls are found on almond, apple, apricot, cherry, euonymus, honeysuckle, juniper, nectarine, plum, maple, oak, raspberry, rose, sycamore, walnut and willow plants. Trees and shrubs almost never attacked include andromeda, beech, birch, black gum, boxwood, cedar, cryptomeria, deutzia, firethorn, hemlock, holly, magnolia, mimosa, redbud and tuliptree.
The disease is caused by soil bacteria, which transfers infected nucleic acid into a wound on a plant, and from there into the cell structure. Galls generally average several inches in diameter, even massive on tree trunks. Most gardeners think of galls as "black knots."
Should you find any galls on shrubs or trees, remove them soon afterward. Disinfect the cutting edges of hand pruners or pole-tree pruners between cuts with a solution of one part chlorine bleach to five parts water.
Remove aluminum foil and jute wrappings from trunks of dogwood trees now that the borer season is ending. Conversely, if you have not done so already, wrap the trunks of flowering and fruiting fruit trees with jute or aluminum foil to deter the peachtree borer.
Trunks should be wrapped from the soil line to where the first limb veers off the trunk; mound soil over the jute or foil at the base to prevent borers from boring under the wrapping. Remove wrappings in early October.
Trees are under siege by scale, which over-wintered on woody branches and trunks of trees, including ash, beech, locust, maple, oak, sycamore and willow. Scale eggs were laid late last summer and early fall, appearing as clusters of "dirty white snow" on host trees.
Scale recently has exited the egg and is now crawling and feeding on trees, inflicting severe damage as they siphon carbohydrates from the veins of foliage. Scale feasts on leaves for the next few weeks, after which they will start mating and females will lay clusters containing upwards of 1,000 eggs each. July control of scale is essential to prevent another siege next year. Sapling trees should be sprayed with Sevin in the evening hours. Veteran trees within range (25 feet) should be sprayed with liquid Cygon in the cool of the evening with the Ortho tree and shrub hose-end sprayer.
Jack Eden is the host of "Over the Garden Fence" Sundays from 10 a.m. to 1 p.m. on WTOP Radio (1500 AM).