With half of this summer over, gardeners need to start to prepare for the inevitable – winter.
All fertilizing should now stop. The dividing of spring perennials should begin.
The process of dividing those yearly plants will ensure that they stay healthy and provide an abundance of blooms. The standard rule to divide them every three or four years has many advantages.
One of which is that most plants have increased in size since they were planted or last divided. While that is true for all perennials, only spring bloomers should be divided at this time of year.
Fall bloomers are best divided in the spring. That procedure gives them ample time to rejuvenate and prepare for the coming season. They will need time to reestablish themselves.
Divided summer and fall flowering perennials have the whole spring and early summer to grow new roots. Once being transplanted or divided they will provide superb blooms at their regular time of year.
It should be noted that is only a rule of thumb. Often, as the need arises, gardeners experience few problems when transplanting in the growing season. Slicing a blooming perennial in two and quickly replanting may cause some setback, but with proper care and moisture the transplant will be successful. Never allow the plant to dry out.
As long as the plant has a lengthy period of time to recover before flowering again, transplants or divisions of Rock cress (Aubrieta), Basket-of-Gold (Aurinia), Moss phlox (Phlox subulata), Bleeding heart (Dicentra), Pasque flower (Pulsatilla vulgaris), Bloodroot (Sanguinaria canadensis), Heartleaf brunnera (Brunnera macrophylla), Lenten rose Hellebore (Helleborus x hybridus), Candytuft (Iberis sempervirens), and Irises can be safely divided.
Often large clumps of old perennials will start to die out in the center. A telltale sign is the doughnut shape that many acquire, and they need to be uprooted.
Any plant that has begun to give poor flowering performance may be in a state of decline and needs immediate attention. Uprooting large clumps will reveal that the plant has become congested and the roots need thinning.
Often the surrounding soil has been exhausted and would benefit from a good dose of compost.
Or simply uprooting, dividing, and moving to a fresh location can solve the problem.
Generally bearded irises are divided shortly after they flower in July or August. Newer hybrids may flower much later in the summer. If the plan is divide the total collection, it may be prudent to divide and move them all at once.
They are notorious for allowing weeds to grow between the rhizomes. Weeding is an extremely labour-intensive activity that is best solved by uprooting large infested clumps. Grasses can be removed once the rhizomes have been separated from the soil. Tediously, picking out individual grass roots is the only sure way to eradicate them.
Once weeded, large rhizomes can be broken apart to make new plants. Always move the rhizomes to a new location every three to four years.
Increasing the number of your favourites by dividing them is a major advantage for growing perennials. Increasing their representation in your garden or sharing the extras is a great trading community activity.
Offering plants to the local horticultural society is a neighbourly way of sharing the surplus. Often those plants are used in community gardens or they are placed in a plant sale.
Spring is the very best time for dividing most ornamental grasses, and especially the fall-flowering types such as Fountain Grass (Pennisetum) and Maiden grass (Miscanthus).
Once a plant has grown so large that it collides with others it is time to transplant or divide it into several pieces.
It is best to watch for signs of smaller leaves and fewer flowers.
Always divide in cool weather.
That will allow for healthy division and regrowth. If the plant is being transferred to a pot for later planting or distribution, water thoroughly and often.
Keep in a shaded area to assist in rapid recovery.
Ron Stevenson is a member of the Fergus Horticultural Society
