Garden Detective: Butterfly bush, aphids, spider mites

DEAR JESSICA: I know you advise cutting butterfly bushes almost to ground level in early spring, before they break dormancy. Does that apply to a bush that was just planted last summer? Also, do we cut straight across or cut retaining the round shape? -- Don Ambrosio, Commack

DEAR DON: Butterfly bush (Buddleia) should be cut completely down in early spring at just a few inches above ground level. There's no point in trying to retain any shape as new growth will replace it in no time. Although you don't have to cut down a year-old plant, doing so will prevent it from becoming unruly. Gardeners sometimes are apprehensive about cutting back large, older plants, but rest assured, those, too, will return nicely by summer and with a neater shape. Timing is crucial: It's important never to prune them in fall or they'll likely die.

DEAR JESSICA: My hydrangea has been blooming proficiently every year, although last year I noticed aphids under the leaves. I tried spraying them with insecticidal soap. This year as I was clipping the old blooms, I noticed that there are aphids on the stems now and some spider mites starting to infect it. What's the best way to treat and get rid of them? I hate to lose this plant, as it is very pretty. -- Mari James, Sea Cliff

DEAR MARI: Aphids, or plant lice, are tiny parasitical insects with piercing-sucking mouthparts, which they attach to soft plant parts in order to suck the life out of them. They often can be dealt with by rinsing plants with a blast of water from the hose, essentially knocking them off the plant.

While insecticidal soap certainly can be used against aphids, I prefer exploiting the food chain and letting nature take its course. Ladybugs are natural predators of aphids, each capable of consuming anywhere from 75 to 300 aphids per day. So you can imagine what a whole boxful of them will do to your pest population.

Some of the larger nurseries and garden centers on Long Island sell ladybugs for just this purpose, but only in early spring. If you're unable to find them locally, you can buy them online. I found a pack of 900 for $14.95 at Gardens Alive! (the exclamation point is part of their name.) From the website: "One package of about 900 Sta-Home adults will produce more than 10,000 pest-eating larvae in your garden within 30 days! We ship at the proper time for your area or on the date you specify."

Spider mites also are targeted by ladybugs, so you might be able to kill two pests with one stone. Avoid using general garden pesticides, as they can also eliminate the pests' natural predators and create a bigger problem. If the spider mites are not eliminated along with the aphids and continue to be a problem, look for a miticide or acaricide and follow package directions precisely, reapplying every 10-14 days until control is achieved.

DEAR JESSICA: We have 40 mature, 8-year-old arborvitaes that this past year have become deer food. These trees, which had provided our back and side yards with a natural border, are now so naked that we can see through to neighboring yards. We live in Shoreham, where small herds of deer live. Someone suggested topping these lovely trees to spur growth on the eaten lower half. Do you have any suggestions?

-- Michael Genzale, Shoreham

DEAR MICHAEL: Unfortunately, there is nothing that will help sufficiently fill in the lower half of your trees. That's why it's so important to be careful to retain a wider-at-the-bottom shape when pruning evergreens. I understand this wasn't your fault and your deer visitors weren't likely aware of this protocol, but nonetheless, you're left with the damage.

Topping is something that absolutely, positively should never be done to any tree for any purpose. Although trimming branches does spur new growth from those same branches, it won't help other branches.

As you've noticed, arborvitaes are a favorite food of deer, especially during winter when other food is scarce. The trees usually can recover from minor deer browsing damage, but if the lower branches are, in fact, naked, they likely are past the point of no return. The good news is that this doesn't mean you have to remove the trees. Water them during dry spells over the summer and fertilize with a product labeled for use on evergreens in May to keep them healthy and possibly even get some new growth. Then plant some low-growing junipers or other evergreen shrubs in front of them to block the damage.

To prevent further damage, alternate monthly applications of Deer Off and Deer Fence repellents, sticking to just Deer Fence during winter months.