Q: I live outside of Baltimore MD and I also have a home in Southern Delaware. I want to move to Delaware an established lilac, Chinese Maple and two rhododendrons.

When do I do this (time of year)? How critical is the root structure? Do I have to have a backhoe to get enough of the roots.

A: The size of the rootball is determined by the size of the plant, so if you have large plants you'll need large rootballs. A backhoe may be needed, if you want to save digging energy.

For the rhododendrons, you could dig them in September.

As for the lilac and maple, I would wait until they're going dormant for the winter (any time after the first hard frost). Deciduous trees prefer being dug up when they're "napping".

To determine rootball size, measure the diameter of the trunk about 6" above ground level. Dig 10-12" of rootball for every inch of trunk diameter, i.e., if the trunk is 3" in diameter the rootball should be 30-36" in diameter.

This should get you the minimum amount of roots for the plant to survive the move, but it's still always a risk when transplanting.

Before digging, water the plants thoroughly 7 days before the move and again 2-3 days ahead. This will get them well-hydrated, and will also moisten the soil (slightly moist soil holds a rootball a little better than dry soil).

When they're planted, water once a week as needed, checking the soil moisture first to be sure they need watering.