While summer maintenance chores demand considerable time on summer weekday evenings, a handful of serious garden projects await your attention as we close out the first week of July.
Here are some tasks to nip problems in the bud:
Check host shrubs and trees now for evidence of fireblight disease. Fireblight persists until it is surgically removed, so if you find it the pruning needs to be done now. Fireblight shows up as limp, black leaves hanging from limbs of apple, apricot, brambles, cherry, chokeberry, crab apple, cotoneaster, hawthorn, kerria, mountain-ash, pear, photinia, plum, pyracantha, quince, raspberry, rose and spirea.
Some varieties are more susceptible than others. With apple trees, fireblight is almost certain on Idared, Jonathan, Rome Beauty and Wealthy varieties. With pear trees, Bartlett, Bosc and Clapp's Favorite, and Flemish Beauty attract fireblight worst of all. Common pyracantha is a target, but "Everlasting Thorn" pyracantha resists the disease. "Rock Spray" cotoneaster is also immune.
Over-fertilized trees and shrubs are vulnerable to the disease, which enters the plant through blossoms, fruit spurs, foliage and then twigs. As spores move from cell to cell along a branch, reddish-brown cankers develop in the sapwood. Leaves along the diseased limb turn black, as if scorched by fire.
If you find any blackened leaves on shrubs or trees, prune immediately to eliminate the disease. Pencil-thin limbs may be cut with pruning shears, but thicker branches require the use of a pole-tree pruner.
In every case, move three to five inches inside the innermost black leaf and cut at that point. When the branch falls to the ground, scrape away the outer bark to make sure that the red-black color of the cambium has not progressed to the point of pruning. As long as the dark color is some distance away from the cut, the disease has been eliminated.
Between cuts, wash down the cutting edges of the pruner or the pole-tree pruner with a rag dipped in a solution of one part chlorine bleach to five parts water. This kills any fireblight spores that may come in contact with the cutting edges of the tools.
Despite the product claims, the spring "fireblight spray" of 17.6 percent streptomycin sulfate will not kill fireblight spores that have previously entered the plant. However, spraying just-opened flowers in April with the product will prevent fireblight spores from entering the plant.
Peach tree borer season is here, so wrap the trunks of host trees this weekend with jute or aluminum foil, wrapping from the soil line up to where the first limb veers off the trunk. Wrap firmly, overlapping a bit. Mound soil up and over the wrapping at the base of the trunk to prevent borer entry there. At the top, seal with masking tape. This borer is the primary assassin of apricot, cherry (flowering and fruiting), nectarine, peach and plum trees. Wrappings should remain in place until Columbus Day.
June-bearing strawberry plants are yielding their last fruits, in which case you should plan on spading these two-year-old plants from the garden next weekend. As for the 1991 harvest, we hope you bought year-old June-bearing strawberry plants in the spring, in which case you're certain to enjoy the fruits next June. If you failed to buy plants back in the spring, get the garden shop on the phone now to seek out year-old plants. Ideally, these new plants will be planted over the next two weeks in the very rows from which older plants are soon to be spaded. We'll update this in next week's column.
Fruiting cherry trees are now surrendering their fruits (sweet and tart), but the concern for the moment is how the leaves are doing. Check your trees now. Do you find tiny holes in the leaves, not a handful, but a lot? If so, you have a problem on your hands.
Over the next three weeks, leaves with holes are going to drop from the tree; they have to because they're diseased. It's called cherry leaf spot, but in tree circles it's best known as "shot-hole" disease because the leaves appear to have been damaged by a shotgun. The disease is in the "doughnut" holes that have fallen from the leaves, so this gives you some idea of the difficult task confronting you.
First, there is nothing you can do for the moment; do not fertilize the cherry tree under any conditions.
Second, the leaves will stop falling in a few weeks, at which time you should remove any mulch below and around the tree. The rationale is that diseased "doughnuts" are embedded in the mulch, so by removing the mulch you also remove the source of next spring's infection. At the same time, spade any grass under the tree canopy, turning it over and burying disease spores in the soil at the same time.
Finally, healthy leaves will remain on the tree until late October. When they drop, every leaf must be removed from the soil. In the absence of mulch, bamboo raking of the area will suffice. Soil should be left bare over the winter. Come March 15-25 next year, you should bring in pine bark nuggets to mulch the soil under and around the tree, and "shot-hole" disease will be history.
Don't be shocked to find a massive leaf drop in the next two weeks with peach and nectarine trees, especially in view of the cool, damp spring this year. Yes, you could have circumvented the problem had you sprayed lime-sulfur on woody branches last November or late March of this year, but that's spilled milk. The question is what to do now?
For the moment, there is nothing you can do. The damage is history.
Peach leaf curl is a disease striking neglected nectarine and peach trees. Spores spend the winter on woody tree limbs and infect flower buds as they begin to swell. Spraying buds after swelling occurs isn't productive since the spores have already invaded plant tissue. Sprayed in November or mid-March, lime-sulfur kills overwintering spores, thereby breaking the disease cycle.
However, as leaves drop from host trees, set the stage for disease control by weekly raking of fallen leaves from the soil. By doing so, you will minimize spores wind-blown to the trees in early fall.
Forgetting the daily soaking of window-boxes and container plants proves that nobody is perfect, including us. Remember that every plant needs almost a quart (32 ounces) of water every day, so omitting the water jeopardizes the plants you've worked so hard to save. If you've somehow lost plants along the way, raid the budget for replacements and get them planted right away. Bring home some charcoal from the garden shop to work into the soil before setting in the replacements.
Rejuvenate the bedding garden this weekend or next. Fertilizer applied in late April has long since run its course, so prospects for summer and early fall flowers hinge on a second feeding now. Apply one pound of 5-10-5 inorganic for each 100 square feet of bedding garden, sprinkling the granules over the soil or mulch, not on plants. A 12-ounce coffee can filled almost halfway provides one pound of fertilizer.
At the same time, prune all annuals (not perennials) back to within five inches of the ground. This removes any accumulated "auxin," a growth-inhibiting hormone, in upper cell tissue, thereby promoting substantial reflowering of all annuals up to the first killing frost. Plants so pruned include asters, geraniums, marigolds and petunias.
Also run a check of soil pH in view of the strong chance that it has dropped from the favorable range. Any test showing a pH below 6.5 justifies an immediate application of pulverized lime to set things straight. Sandy soils will have to be limed every other week.
If you have youngsters, start a children's garden of some size as their first venture with plants. Start with seeds for annuals, instructing the children how to plant and water. Accompany them on the daily rounds of their garden to instill a sense of commitment and responsibility. Shower them with praise so their initial plant experience is rewarding. Jack Eden is the host of "Over the Garden Fence" Sundays from 10 a.m. to 1 p.m. on WTOP Radio (1500 AM).