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Last year, I planted healthy Purple Wave petunia plants in a container, but they hardly grew and hardly bloomed. I’ve seen great Purple Wave plants everywhere in the past. What did I do wrong last season?

Without knowing your exact environmental conditions last year, we will try to give some possible reasons things could have gone wrong. Any petunia will require at least 6 hours of sun a day. Any less than that will cause low bud counts and stringy-looking plants.

Using improper soil for a container-grown plant could be another reason. Stay away from topsoil, which is too heavy, holds too much moisture, and restricts root growth. Use a light, “soilless” mix with peat and perlite.

Fertilize every other week with a 20-20-20 fertilizer. “Wave” petunias are rapid growers and heavy feeders. Use a container large enough to let those Wave petunias grow. A pot no smaller than 12 inches would be best.

My rhododendron has a black, sooty substance on its leaves and stems. What is it and how can I correct this problem?

That black substance is probably sooty mold growing on the deposits of honeydew (excrement) left by an insect. It is often a homeowners’ first sign of trouble in the landscape. Aphids, scales, whiteflies and mealybugs produce this sugary, sticky substance. They all feed by piercing and sucking a plant’s juices. The sooty mold itself does not injure the plant. But if left untreated, it will shade the leaves, reduce growth, and invite other unwanted guests to dinner.

You can simply wipe off the sooty mold. More importantly, you need to find the source of the honeydew. Be sure to consider where your rhododendron is planted. If it is positioned as an understory feature with taller trees, your plant may not be infested itself, but merely be the honeydew recipient of an “abovestory” tree problem.

Examine your plant carefully, using a magnifying glass if necessary to identify the culprit. Aphids are a maximum of 1/8-inch long, pear-shaped, and green, pink, black, dusty gray or white fluffy-coated insects that cluster on leaves, buds, and young stems. To see if you have whiteflies, just shake a branch. The winged adults are visible and will temporarily fly away. Scales species appear as white, gray or brown bumps on the undersides of the leaves. Mealybugs are soft, oval, 1/10-inch long insects with distinctly segmented pinkish bodies.

Once you’ve identified the insect, you can select a control. Follow the control product’s directions for repeat applications. The watchwords for you are vigilance and diligence to keep the insects from making your plant a five-star restaurant!

My garden does not receive a lot of sun; it’s mostly dappled shade throughout the day. Are there any vegetables and/or fruits I can grow?

Fruits need full sun to flower and set fruit, but there are some vegetables that will tolerate partial shade. Many of these are members of the cabbage family: broccoli, cauliflower, Brussels sprouts, and cabbage. Some other nice, green “leafies” that will grow in partial shade are the many varieties of lettuce, spinach and Swiss chard. Last on the list are some of the underground veggies: beets, potatoes, radishes and turnips.

I have been growing sweet pea vines, but they have no blooms. The vines are healthy-looking; what can I do to get them to bloom?

Sweet peas are an old-fashioned, vining garden flower presently enjoying a new burst of popularity. They are normally easy garden plants to grow, requiring only an average garden soil with reasonable drainage and a sunny location.

They are cool season crops, like their garden cousins. They will grow and bloom best when cooler temperatures prevail. Sow them early in the spring garden (early to mid-April). For an earlier jump, start them inside 4 to 6 weeks earlier. Like most legumes, treating the seeds with a legume inoculant prior to planting will help insure a stronger start.

The earlier planting can net a more bountiful harvest of flowers because they will reach blooming age while the weather is still on the cool side. Once the weather gets too warm, blooming slows or stops altogether.

Will reseeding plants like spider flower (Cleome), Verbena bonariensis, cosmos, and others successfully seed themselves through 2 inches of mulch applied last fall?

Well… yes and no. The three annuals (and might I add, prolific reseeders) that you mentioned are sure to show up again in your garden, however, not necessarily where you wanted them. They won’t actually start sprouting with a good cover of mulch. Assuming that you had mulched with a shredded wood material, the myriad of seedlings cast upon the wind will most likely end up in the cracks of your (and possibly your neighbors) flagstone, and practically any spot where it can reach the bare soil. All three of these annuals can easily be lifted and relocated back into your garden. Then next fall, if you clear a patch of mulch from the soil and shake a few dried seed heads over the soil in the desired garden bed, you’ll more than likely get at least a few in the “right” spot.

While tilling my perennial beds this spring, I noticed small orange-yellow, worm-like insects (roughly 1/8 inch in diameter and 1 inch long). What are they? Are they good guys or bad guys?

Sounds like you’ve got a crop of wireworm (Limonius spp.) larvae crawling in your perennial bed. These larvae are more foes than friends. Wireworm larvae are slender, orange-brown creatures with three pairs of short legs close to their head. They can be up to 1 inch long. The larvae have a small knob toward their rear on the underside. Larvae damage or kill plants by devouring seeds and boring into roots, tubers, and bulbs. Their appetite for gladiolus corms, potatoes, and carrots, among others, is heightened in soil previously planted with lawn grass.

Adult beetles, unlike their progeny, feast on leaves and flowers but cause little damage. These hard-shelled, elongated, dark-colored, 1/3- to 3/4-inch long beetles are also called click beetles because they make a clicking noise as they flip over from back to front. Every spring, females lay eggs on plant roots. Although the eggs hatch in 3 to 10 days, wireworm larvae spend the next two to six years dining on roots, tubers and bulbs in the spring and fall. They burrow deeper into the soil during the winter. Once mature, the larvae pupate in late summer.

You can manage the wireworm larvae population by working an appropriate insecticide into the top 6 to 8 inches of soil. Some experts suggest burying raw potato pieces 4 to 6 inches deep to attract larvae, checking the potatoes every other day to destroy the larvae. Applying parasitic nematodes to soil could also discourage these larvae.

I have a row of evergreen azaleas growing near my concrete driveway. The first couple seasons they looked very good, but now they look worse every year. The foliage is turning more and more yellow. Can these plants be saved?

The symptoms you describe appear to be iron chlorosis. This is a very common problem in acid-loving plants like azaleas. It is caused by a deficiency of iron in plant tissues. Although soil is seldom deficient in iron, the iron is often in a form that the plant cannot take up through its roots. This is especially true when the soil’s pH is 7 or higher. Plants located near concrete driveways, paths or walls are especially susceptible to chlorosis.

First, get your soil pH tested. There are several reliable products on the market that can correct the problem. Make sure the product label is followed correctly in accordance with the results of your soil test. Depending on the results, you can increase the soil acidity by adding the correct proportions of iron sulfate, ammonium sulfate, or sulfur. You can also mulch the soil with leaf mold or pine needles in combination with the application of an appropriate fertilizer for acid-loving plants. With some immediate treatment and moderate long-term maintenance, your azaleas should be looking as good as they did when you first planted them.