<b>Maeve asks:</b> When is the recommended period of time to prune the vertical water sprouts out of my ornamental plum tree? Each year they grow several feet.

Plum trees are recognized for their tendency to produce prolific water sprouts and, if not removed, they literally take over the tree, producing shade so the limbs and foliage become starved for sunlight. Not only do they create a shade problem, they prevent the wind from flowing through the tree canopy, and even more importantly, they rob the rest of the tree of energy that is needed for the tree to thrive and keep its attractive form.

Now to answer your question: Most gardeners will prune out the tall sprouts, sometimes 5 feet or more in length, when the tree is dormant since it is much easier to visualize one's pruning cuts when the leaves have fallen.

I prefer to keep ahead of the on-going problem and prune out the newly forming water sprouts midsummer, and as needed, again during dormancy. Summer pruning doesn't seem to invigorate the sprout growth as much as the traditional dormant pruning. Whenever you choose to remove the vigorous vertical sprouts, remember, pruning in any form always stimulates new growth near cuts.

When removing the sprouts, use caution not to cut too deeply into the main limb as that can leave an open wound that will not heal as readily.

<b>Mike asks:</b> What is wrong with my boxwood? The hedge has been in this location for several years and then all of a sudden one of them will start to turn brown-yellow and dieback begins.

There are two immediate cultural problems that can cause dieback: Poor draining soil that is waterlogged or very dry soil. Perhaps you have failed to check on the soil moisture, thinking that during the winter it isn't necessary to waste water.

Our cold weather can also add to the problem. If you see some new growth down in the center of the shrubs, prune the dead sections out above the new growth and add some mulch at their base, keeping the mulch away from the main stem. Surface mulch will aid in breaking up the soil compaction.

The other possibility is you might have a soil-borne fungal disease called phytophthora root rot. Dieback symptoms can fit into this category if your soil is heavily compacted, doesn't drain well and is overly moist. Cut out the dead areas of the shrub and see if the tissue under the bark, close to ground level, shows a dark discoloration.

If this is the case, the fungus may have become established in the soil and then it is best to remove the diseased shrub and substitute a shrub that is resistant to the fungus.

If you are reluctant to replace the diseased boxwood, since it is an important part of your landscape, try this:

Dig up all of the diseased boxwood and as much of the surrounding soil as possible. Replace the soil with new, uninfected soil and plant new boxwood. This solution has been known to be successful and is worth a try.

<b>Katie asks:</b> Can I plant an Italian stone pine tree outside after it has been used as a small Christmas tree? How large will it grow? Any other information you can offer is appreciated.

Yes, you can plant the tree outside, but it will probably need help adjusting to the cooler outside temperatures since it was grown under greenhouse conditions and then has been in a warm house during the holidays.

Place the container tree in a sheltered and sunny warm spot during the day for several weeks and protect it at night. (A frost-free cover placed over the tree should be sufficient.) Even though it can tolerate a temperature range of 10 to 90 degrees F. once established, it really prefers temperatures of 50 to 75 degrees F. until it is acclimatized.

Do not let the soil dry out, especially while it is still in the container, or allow it to remain in standing water in a tray under the pot.

When it is time to plant the tree outside, give it some timed-release fertilizer and the soil should be amended with peat moss or a 50:50 ratio of fir bark mixed into the native soil to promote good draining.

Italian stone pine, Pinus pinea, can reach heights of 40 to 80 feet and grow as wide as 40 to 60 feet. Obviously, this is not a pine for a small garden and space should be a major consideration before planting. It will tolerate heat and has an attractive flat-topped globe appearance. It is a perfect choice for a beach property that has an abundance of acreage.

<i>Send your gardening questions to The Garden Doctors at pdgardendoctor@gmail.com. The Garden Doctors, gardening consultants Gwen Kilchherr and Dana Lozano, can answer questions only through their column, which appears twice a month in the newspaper and online at pressdemocrat.com.</i>