I know that dandelions are deep-rooting. Can anyone advise me on other plants with this characteristic?
I am especially interested in shrubs, and in plants that will grow in shade.

Thanks in advance!

Do you consider alfalfa to be a shrub? It might not do well in the shade. What about clover? Not much height with Dutch white clover, but crimson is much taller.

I am truly curious about the prerequisite of it being a deep-rooting plant. At what depth do you consider something to be deep-rooting and where would information like that be kept for plants? I have never seen that statistic mentioned.

I never thought about how deep... A friend of mine asked this question of me and I did not know so I took to the forums! Some plants have deep tap roots, more deep than others. I will look into this elsewhere and report back soon as I am able.

I am just wondering what situation she has that would have prompted such a prerequisite. Maybe wanting deep-rooted so they are more drought tolerant?

I believe that she wanted more drought tolerant plants. She knows to use native or adapted plants. I believe she is also looking for serious erosion control. I do not think the area gets much sun...

I would direct her to Sally Wasowski's "Native Texas Plants" book which details ground cover (and everything else) for all soil and sun types. It's an excellent book.