Divide perennials in the fall

With fall and cold weather approaching, it’s time to think about and prepare for dividing perennials. For those of you who are new to gardening, this is a way to get free plants and rejuvenate some perennials that have stopped flowering, have bare clustered areas where some have died, or have simply lost vigor.

The general dividing guidelines are that spring bloomers should be divided in the fall while fall bloomers should be divided in the spring. By doing this, most of them will bloom without missing a season. But many of them can be divided at any time if you can accept skipping the flowering season. In addition, some warm-weather-loving perennials and some winter-hardy plants in your garden are best divided in the spring because they may not have time to root before a hard freeze kills them.

Examples of plants that can be divided in the fall (some can also be divided in the spring) are mat-forming Dianthus spp (cloves and pinks) and Rudbeckia spp. (Black-eyed Susan), Echinacea purpurea (Purple Coneflower), Coreopsis grandiflora, Salvia spp., Hemerocallis spp. (Daylilies) and others. Bearded iris can be divided in August as well as later in the fall.

Try to work when it is cool or cloudy. Before dividing, water the plants to be divided until they are completely hydrated. It will also make drilling easier. If possible, prepare the area where the divisions will be planted before digging and dividing to minimize transplant shock. If this is not possible, keep the sections moist and away from heat. If necessary, they can be planted temporarily in a temporary location or in containers for care until they are planted in their final location. These methods can also be used if you waive them.

Most perennials are easily divided. Depending on the plant, dig up the clump or cut off part of it and examine the roots. Some, like daylilies and irises in general, will break apart easily or can be cut. Others will need to be chopped up with a knife, shovel, or other tool that will do the job easily. Some plants with woody stems may need to be cut down with a saw or axe. Remove dead material and damaged roots and stems.

Making fewer large divisions will create a new variety more quickly, but if you need more plants, use smaller cuttings. In any case, make sure it has a number of good, healthy roots attached to the stems to support its leaves.

Plant at the same depth they were growing by looking at the stems to see the soil line. Since iris is planted shallowly in the ground with the rhizome exposed, cut the leaves into a short fan to help prevent them from blowing away before putting in new rhizomes to anchor them. For plants like sage, I usually thin the foliage significantly to reduce stress from too few roots trying to keep too much foliage moist.

Mulch and keep plants moist until established.

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