Garden Detective: Scotch broom, squash problems

DEAR JESSICA: I have two Scotch broom plants. When is the best time of year to prune? Should they be cut back?--Gail Slotnick, Plainview

DEAR GAIL: I love Scotch broom -- for the first couple of years -- then I usually want to take a blow torch to it!

The beautiful, old-fashioned, spring-flowering shrub is a member of the pea family. It's quite charming in the beginning, but typically becomes top heavy and flops over onto the ground after a few years. And it doesn't respond well to rejuvenation pruning; cutting it to the ground or even halfway down won't necessarily stimulate healthy new growth.

So, what to do? If you want to keep this plant around (I've spoken to many gardeners who consider them temporary and rip them out when they begin to misbehave), you certainly can do so, and pretty easily, too: Just completely remove about 20 percent of the stems, cutting them all the way back to the base. You can do this safely at any time of year.

DEAR JESSICA: Could you please tell me how to treat squash in the garden? Every year, mine are attacked by something and die early. This year was the worst.-- Frank,via email

DEAR FRANK: Very likely you have squash vine borers. The pests begin life innocently enough, as beautiful moths. They lay eggs near the base of squash (or cucumber or melon) plants, and when they hatch the larvae bore into the stems and feast on the plant tissue within until it collapses. By the time you realize what's going on, it's often too late. To add insult to injury, they cocoon in the soil, where they survive very nicely over the winter and re-emerge in late spring as orange-and-black moths ready to repeat the carnage. Sometimes there's even a second generation in August. This is why your problem is recurring.

The moths lay eggs only early in the season, so delaying your plantings until, say, the end of June, is a surefire way to avoid the first wave. Another great solution is using floating row covers. Sunlight, water and oxygen can get through these barriers but the moths cannot. Remove the covers in early summer. If those two options aren't practical for you, keep a close eye out for the red, flattened-oval eggs next spring and pick them off plants and the surrounding soil as soon as you find them. You'll need to be vigilant and hunt at least once a week to avoid damage. If you miss some, you'll see the telltale signs of attack: small puncture holes in the bottom portions of the stalks and stems, and frass, or caterpillar excrement, which looks like sawdust.

If it comes to that, slit open punctured stems lengthwise near holes using a razor blade, and pick out the borers. Then mound soil up at the base of the plant to cover the injured part of the stem. This will encourage new roots to grow. If all else fails, use a product labeled for use against squash borers, such as all-natural Btk, and follow directions precisely.

DEAR JESSICA: I never know what to do with my lavender plant in the fall. Do I cut it all back? Cut some back? I haven't been doing anything, and then in the spring I have been cutting off the dead branches. It is now covered with blooms so maybe I am doing something right. What do you suggest? The next issue is my neighbor's yard. It is covered in ivy, and the ivy is over my fence and invading my yard. Other than Agent Orange, what should I do? I have tried to pull the plants, but being 59 years old, I find that physically challenging.-- Corinne,via email

DEAR CORINNE: I've got good news and bad news. First, the good news: You can cut back lavender either in spring or fall. Aim to maintain a nice shape and remove the dead portions of any stems. And if you trim it back in summer after it blooms, you might get another flush later in the season.

Now, the bad news: English ivy (Hedera helix) is extremely difficult to control. It holds on for dear life with tendrils, aerial roots and a sticky substance called glycosides, which also can cause skin irritation when you're trying to remove it. Standard herbicides are no match for it because the ivy's waxy leaves are virtually impenetrable. I have some growing in my yard, too, thanks to a previous owner, and although I've only tried half-heartedly, I haven't been able to eradicate it, either. Left unchecked, it can take over your entire yard and, as you've learned, your neighbor's yard, too.

Some non-selective herbicides can be very effective. Using them requires a great deal of care because they will kill everything they touch, even grass. Products like Ortho Brush-B-Gon will work, but I can't stress enough that extreme caution is needed because they are root-absorbed and will destroy everything in their paths, including nearby trees.

For you, this doesn't sound like an option, because although the vines are on your property, they're all part of one plant, and you'll likely end up killing the whole thing and alienating your neighbor or even risk becoming embroiled in a legal action. I've heard some crazy stories.

The safest and most effective way to remove it is with lots of physical labor. Cut it down to a few inches from the ground and then pull or dig up the rest, taking care to get the whole root system. Unfortunately, even if you eliminate it from your property, eventually more will likely invade from your neighbor's side.