Final answer:
Clothilde should look in Chapter 3: Caring for Your Herbs for tips on maintaining her elderberry plant to prevent overgrowth.
Step-by-step explanation:
Clothilde, who is looking for tips on maintaining her elderberry plant to avoid another overgrowth, should consult Chapter 3: Caring for Your Herbs in The Big Book of Herbs and Herbal Medicine.
This chapter is likely to contain the information she needs about proper herb care techniques, which would include elderberry among other herbs. Since elderberry is an herbaceous plant, the guidelines in this chapter should provide the necessary advice on effective maintenance practices to prevent overgrowth.