LSU AgCenter Horticulturist
(08/07/20) It’s August in Louisiana, and we don’t recommend doing much in the garden or, shall we say, not much in this heat. Right now, it’s enough of a chore to help our struggling plants survive. It’s best to stay on top of watering, preventing pests and removing weeds from garden beds.
During summer, Southern turfgrasses and tropical plants are thriving. But most of our annual bedding plants, shrubs and trees are just trying to stick out the heat.
One thing you can do this month besides getting fall vegetable garden seeds started or planning big landscape installations for the fall is to dig up and divide perennial flowering plants such as daylilies and irises as well as ornamental grasses.
In general, most prolific perennial plants such as lilies, irises and ornamental grasses need to be replanted or divided over time. When you notice plants beginning to decline, it is typically an indication of overcrowding. If you begin to notice a decrease in the number of flowers and an overall decline in plant health, it’s probably time to divide plants.
Plants that are overcrowded begin to decline in vigor and health due to increased competition for sunlight, nutrients and water. This will be most noticeable when plants start to look a bit ragged.
Signs usually manifest when clumps begin to decline and die out in the center, and they may stop flower production altogether. When you begin to notice this decline, it’s time to start dividing the plants to help decrease competition for nutrients and water.
It’s best to try to accomplish this task first thing in the morning or in late evening when the temperatures are not too hot. When dividing plants, use a spade or shovel to carefully lift the clump of plants from out of the ground. Be careful and try to prevent as little damage to roots as possible. When you’ve got a good clump out of the ground, use a garden knife or spade to cut clumps into smaller pieces for transplanting.
Transplant to a new container or in another portion of the lawn or share them with friends or family. Be sure to water plants in well to avoid added stress. Continue to watch plants over the next few weeks to ensure adequate water as they establish new root systems.
Dividing and replanting during the late summer and early fall allow plants to establish a good root system before going into dormancy during cooler winter months.
Overall, perennials are best divided in the very early spring when they are just breaking dormancy or in the late summer after they have stopped flowering and begin looking a bit ragged. Avoid disturbing perennials when they are forming flower buds or are in bloom.
Overcrowded daylilies can be divided and replanted after flowering. LSU AgCenter file photo
Irises, like these in a rain garden, can be thinned and transplanted during August. Photo by Rick Bogren/LSU AgCenter