If Shasta daisies and black-eyed Susans are crowding out other plants in a perennial bed, you can dig and divide them in the fall to rejuvenate them.
Both have a tendency to grow thin at the center of a clump of plants, and especially for black-eyed Susans, garden author Troy Marden, in his Southern Gardener’s Handbook, suggests digging vigorous plants from the edges of the clump and transplanting them back to the middle, so that the clump remains full.
Editors of the Southern Living Garden Book suggest this method for digging and dividing perennials: use a shovel or spading fork to cut into the soil 6 – 12 inches beyond the plant’s perimeter, then dig under the roots and lift the clump out of the ground. Tease some of the soil from the root ball, then pull the clump apart, or cut it into sections using clippers or a sharp-bladed shovel. Trim damaged roots, stems or leaves, then replant the divisions.
If you’re moving divisions to a new bed, it’s best to have the bed prepared before you dig them up. Both plants thrive in full sun in well-drained soil that is kept evenly moist. Black-eyed Susans are especially durable once they are established.