Garden detective: To thrive, shamrocks need a rest

I hope you can help me, I am desperate. I have a pot of shamrocks that were given to me in 1989, and they have flourished over these many years and brought me great joy and luck. Just recently I decided to repot them, as they were outgrowing the pot they were in. When I removed them from the pot, I discovered there were two large root plants, so I potted them in separate pots. Since that time, both plants appear to be dying. Is there anything I can do to bring them back? -- Bob Hagan, Kings Park

Shamrocks are revered by the Irish because St. Patrick is said to have used them as a visual prop to explain the complexity of the Trinity: three parts, one leaf; three beings, one God. Ever since, the plants have been thought to bring good luck and have even become the national symbol of Ireland. The word "shamrock" comes from the Celtic seamrog, which means little clover. We don't really know what kind of little clover St. Patrick used, but we assume, perhaps incorrectly, it was black medic or common white or red clover. However, the plant being sold as a shamrock today is actually Oxalis regnellii, which grows from a rhizome and sends up compound leaves, comprised of three triangular leaflets, atop 6-inch-long petioles. It flowers profusely in spring, when it's covered with inch-long white, five-petaled trumpets. I spoke with and shared photos with Mr. Hagen to confirm his plants were, indeed, Oxalis regnellii.

Grown as houseplants, these shamrocks should be located near an east- or west-facing window, away from radiators and other heat sources and in a spot free from cold drafts. Your plants might be fine if you allow them to take a rest now. Stop watering and place them in a cool, dark spot for two to three months. Don't panic when the leaves turn brown; just pull them off.

At the end of their hibernation, bring the plants back into the sun, resume watering and give them a dose of 10-10-10 fertilizer. This also would have been the ideal time to divide them, replanting with the root system just below the soil surface. May the luck of the Irish be with you - and your shamrocks.

Dying Rhododendrons might have pests

I have very large rhododendrons that have been dying. In places, the bark is wrinkly and flaky. The leaves turn yellow and get brown spots and holes in them. Is this a fungus or some other kind of disease? How do I treat this? I have had so-called "tree experts" come and spray, but it didn't do anything at all. I have given them food for rhododendrons, but they just keep dying. I don't want to loose these magnificent plants. What can I do? -- Coleen Bruno, Ronkonkoma

It sounds like you might be dealing with rhododendron borers. Larvae tunnel into the bark, weakening the branches until they break off without much effort. The leaves on affected branches also become pale and spotted, which seems to be what you're reporting. To confirm whether this is the problem, break off a branch and look inside it for tunnels created by the borer. If you see that telltale sign, cut away any affected branches, and if the problem continues in spring, use an insecticidal spray containing chlorpyrifos. Timing is important for maximum effectiveness, so you'll need to know when the adults are out and about. Buy some pheromone traps, and treat the plant seven to 10 days after the first borer is captured. Then prune out affected branches in late summer.

If you do not see tunnels inside branches, it's possible a fungus is to blame. Rhododendrons require well-draining soil and adequate air circulation. The presence of heavy clay soil and the practices of watering too much or late in the day could create a perfect breeding ground for fungi. In my experience, except for during drought, established rhododendrons don't really need any supplemental irrigation. Fungal diseases should be addressed by applying a fungicide in late spring.

Maple can be saved after snow removal damage

My poor miniature Japanese maple lost three branches due to heavy snow blown on it from snow removal from my driveway and front path. It was planted two years ago, and unfortunately both the landscaper and I did not think of this area as a risk for when it snows. Some branches are completely off, but one is still hanging on barely. Is there anything I should do now? Transplant in spring? -- Phyllis Celli, East Northport

Certainly cut back any broken branches immediately, especially the one that is barely hanging on. This month, you can safely move the tree.

To get as much of the root system as possible, you'll need to dig a large hole. If the trunk is 2 inches in diameter, dig a hole at least 9 inches out from the tree in all directions.. If the trunk is thicker, then, naturally the hole should be wider. It's a good idea to wrap the roots in burlap or plastic and tie it into place before moving the tree. This will minimize the mess and keep the roots together while you haul it to another part of your yard.

Move the tree, remove the burlap or plastic and plant the tree in the desired location in a hole the same depth as the one you dug to remove it. Apply mulch and water the tree immediately. Set a drip hose around the tree and water regularly throughout the year.