Q: We just had the city out to fix our backed up water and they pulled a lot of roots out of the pipes. We had it cleaned 6 months ago but the worker said that tree roots actually grow faster in winter. Is this true and if so - why?

A: Yes, indeed, it is true that roots do most of their growing at a time of year many would least expect it - fall and early winter. As to why, all I can say is, "Because Nature made it that way."

When the crown of a tree begins to enter dormancy in autumn, we get to experience its splendiferous fall colors. However, although the top is "going to sleep" for the winter, the roots are just beginning their greatest period of growth activity. They grow up until the ground freezes deeply, at which point they become inactive.

Notice I said "inactive", not "dormant". Roots don't really go dormant like the crown of a tree does. During their "inactive" phase, they can easily be "awoken" to begin growing again if the ground temperature warms up. So, if we have a warm winter where the ground barely freezes, roots can actually be growing just about all winter long.

As to why they got into your sewer, there must be a breech in it somewhere. Tree roots can discover breaks very easily, and when they do, they're in the sewer. They don't "break in", they just discover an opening and take advantage of it.

You probably have the old clay-tile-laid-end-to-end sewer system, which can move around as the ground shifts over time. When the tiles move around, plenty of small openings develop and Voila, tree root invasion.

Short of having your sewer system replaced, which would be expensive, you may have to resign yourself to having the sewer snaked periodically.

You can also try copper sulphate, which supposedly kills the tips of the roots as they begin to sneak into the sewer. Many hardware and building supply stores carry this product. Read and follow the label directions very carefully, and Good Luck!