Learn how to revive an overgrown succulent garden. See: Why You Really Need Rocks. See why in my review below. In garden beds and those areas that guests see first or are likely to linger, be vigilant about weeding. The needle-like structures present on the surface of cactus are known as spines and represent modified leaves. The plump leaves of the plant tend to be a grayish-blue with a hint of pink. This will enable you to identify hidden pests, and treat each plant individually rather than the whole garden. In my book Designing with Succulents (2nd Ed.), I explore this subject.