Question: Can I use pre-emergent weedkillers around my trees and shrubs? How about in my flower beds?
Answer: In theory, pre-emergent weedkillers attack only the seeds as they start to sprout. As a result, they should be safe around any existing trees and shrubs. Nonetheless, you always want to read the directions very carefully before applying them. As for the flower beds, your nurseryman can recommend two or three pre-emergents whose prime use is in perennial gardens to stop the growth of crabgrass and other annual grassy weeds.