Rabbits, rotted zucchini, mystery plants and more gardening questions solved

DEAR JESSICA: Any idea what this plant is? It comes up every year and spreads itself even though I yank it before it blooms. Its flowers are dusty pink, and the vein running through the leaf is also pink. — Jennifer Siegel, West Babylon

DEAR JENNIFER: That's common milkweed (Asclepias syriaca). You've likely been seeing butterfly activity in the area; that's because species of this plant, also called butterfly weed, are the only food sources consumed by monarch butterfly caterpillars. Eating its leaves actually makes the butterflies poisonous to birds — who somehow know it — so it also serves as a natural protection from predators.

The plant, a tender perennial that won't survive our winters, grows 5 to 6 feet tall and self sows, which explains why it keeps returning. If you want to contain its spread, remove seed pods before they burst open in fall.

I do recommend, however, that you allow at least some it to remain in your garden. The plant, which often grows in the wild, has been diminishing in recent years. Without it, the monarchs, whose population already is dwindling, would become extinct, so I'd encourage every gardener to plant at least a little milkweed — even if in an out-of-the way spot. Not only are they beautiful, monarch butterflies are important pollinators.

DEAR JESSICA: Last year for Mother's Day, my son bought his mother a miniature rose bush from our local Stop & Shop. It did well over the summer and when fall came we brought it indoors, but it didn't do well. I brought it back outside after Memorial Day, and it is thriving again. I never see mini roses outside of supermarkets. Will it survive winter in our zone? — Frank Kolovich, Islip

DEAR FRANK: Despite their delicate appearance, miniature roses are quite tough. They can handle winters in our Zone 7 — as well as all the way down to Zone 5. 

You are correct in observing that these plants typically are sold only in supermarkets. They might show up at other retail outlets, but mostly, they're sold in foil-wrapped pots for gift-giving.

Miniature roses have the same cultural requirements — and pest and disease vulnerabilities — as full-size roses, except they require more water. Outdoors, plant them in an area where they will receive full sun, and keep the soil consistently moist (but not soggy). Fertilize every three to four weeks during the growing season, and prune in early spring, before they emerge from dormancy. 

DEAR JESSICA: I hope you can help identify this daisy/mumlike flower planted by our landscaper about 10 years ago. The first few years, it grew with a defined center stalk (about 5 feet tall) with many "branches" — all covered with yellow flowers. Now it's more of a 3- to 4-foot-tall bush with lots of branches, all covered with flowers. Either way it looks spectacular. It's at the end of our driveway and gets lots of attention when it's in full bloom in late summer to fall. — Irmgard Prenner, Franklin Square

DEAR IRMGARD: That's Helianthus salicifolius, a perennial commonly called willowleaf sunflower. Typically growing 4- to 6-feet tall with a spread of up to 20 inches, it is well-suited for the back of the bed, as I see yours are planted behind a border of Liriope (lily turf). 

Its seeds are a good food source for birds, and the plant attracts bees and butterflies, as well. The plant spreads via underground roots, so you may find yourself pulling up unwanted seedlings, but I wouldn't classify it as invasive. It can be divided as needed (do so in spring, just as it comes out of dormancy.)

I'm wondering if the area where it's planted was more shaded the first few years — was a nearby tree removed? Willowleaf sunflower typically is shorter and fuller when grown in full sun. It can tolerate a bit of shade, but grows taller and spindlier under those conditions.

DEAR JESSICA: I am growing impatiens in a planter. Although they're nice and full, how come the petals are discolored? — Jen Randel, Holbrook

DEAR JEN: Because your plants appear to be thriving — there's no sign of wilt, and the foliage looks healthy — I'm confident ruling out disease.

Sometimes, overexposure to sunlight can "bleach" blooms. In addition, some impatiens do this as their flowers age. There's no cause for concern; it's just cosmetic. If it bothers you, you might move the planter into an area that's a bit more shaded. 

DEAR JESSICA: I planted this crape myrtle about two months ago. It looks healthy except the tips of some branches do not have leaves. The leaves that are on the insides of the branches look healthy. Should I clip the tips that look dead or leave it alone? How much water should I give this tree? — Janet Dwyer, Kings Park

DEAR JANET: It appears the branch tips on your tree are dead, but there's only one way to know for sure: Scratch off a small section of bark from the leafless portion of each branch (using your fingernail) and check the color of the tissue within. If it's green, the wood is alive and should eventually leaf out; if it's not green, that portion of branch is dead and should be pruned away (always prune on the diagonal, just before a lateral branch).

Since you just planted the tree in spring, it wasn't exposed to the erratic weather we had last winter while in your yard, but we don't know where it came from or what the conditions were. Oftentimes — and especially this year — crape myrtles, many of which are borderline for our climate — can suffer branch die back over winter. Another possibility is that the roots aren't establishing well, and that could be due to improper planting, an obstruction in the soil or even the tree being rootbound when you got it. The latter would be more likely if it came in a pot rather than being balled and burlapped, but if it was B&B'd, there's a chance roots were damaged when it was dug up from its original home. 

Crape myrtles are pretty drought resistant once they're established, but you should water your tree deeply once a week (unless it rains) during its first growing season in your garden.

DEAR JESSICA: We planted vegetable seeds several weeks ago, and the young plants were eaten by rabbits. Please advise how to prevent rabbits from eating young plants. — Ed Lee, Bethpage

DEAR ED: You'll see all sorts of repellents sold in stores and find countless home remedies online — and some offer (limited) success. But the most effective way to keep rabbits away from your plants is to install chicken wire around garden beds. Nearly foolproof, a 30- to 36-inch fence with mesh openings of an inch or smaller is your best bet. Rabbits do tend to dig, so the fence should penetrate 8 inches below the soil line. Never use chemicals or mothballs (or flakes), as they are toxic and carcinogenic to humans and pets.

DEAR JESSICA: When I got home from vacation the end of May I realized my Knockout roses looked dead. They started to grow new canes and even have buds now. I do not know when and if I should cut away the canes that look dead, three bushes are involved. Any advice from you would be greatly appreciated. — Iris Zimmerman, via email

DEAR IRIS: The dieback you're seeing is likely due to the weather. The good news is Knockout roses bloom on new growth. Go go ahead and prune any canes that are dead — just cut them all the way back to a the nearest live branch. 

DEAR JESSICA: I planted four zucchini plants in a raised bed with potting soil around Mother’s Day. I haven’t watered much due to all the rain. I got six nice, fat, healthy zucchini, and now all of the ones that are growing are starting to get mushy and yellow at the tips. Any advice? — Sue Lund, Elmont

DEAR SUE: That's blossom end rot, a disease caused by a calcium deficiency, which typically results from uneven watering. That's because when plants don't get consistent water during the time fruit is developing, calcium won't reach the fruit, and its cells collapse. In addition, when the soil's pH is out of range for the plant (for zucchini, the range should be 6.0 to 6.5) nutrients, including calcium, aren't made available to the plant. Excess nitrogen also can result in rot.

Before planting next year, test your soil (pH test kits are inexpensive and widely available). If the pH registers below 6.0, incorporate dolomitic lime into the soil following the guidelines printed on the package label. In addition, mix a low-nitrogen, slow-release fertilizer into the bed before planting.

One way I like to dose my tomato, pepper, eggplant and squash plants with calcium is with water left over from boiling eggs; it's rich in calcium from the shells so why pour it down the drain? You can also add crushed eggshells to soil at planting time or top dress with them anytime. This won't be enough to reverse blossom end rot, but may prevent it if started early in the season.

For now, treating with a liquid calcium foliar spray such as Enz-Rot or Rot Stop should remedy the problem. Drench leaves completely (until the product drips off); affected fruit won't be cured, obviously, but new fruits that develop should be rot-free.