When to Transplant PCIs: Wait for Fall

Kathleen Sayce

Pacific Coast Iris (PCI) can be so touchy to lift and transplant that gardeners may wait years––letting a particularly choice plant increase in size so that half or more of the clump can be left alone, just in case it really doesn't want to be moved. Translate 'doesn't want to be moved' as 'dies' and you have a pretty good idea of the PCI response to conditions or changes in conditions that it doesn't like. PCI aren't easy plants. They are a good challenge to a gardener's skill set, in a rock gardening sort of a way. The payoff is that when they thrive, the flower show is amazing, and unparalleled in the iris world.

Iris tenax x innominata seedlings in their third year. These plants flower weeks later than modern PCI hybrids, extending flowering from early June into early July. Photo by Kathleen Sayce

I have a pale yellow PCI seedling in my garden that I left to grow an additional year, just in case it doesn't take well to being divided and replanted. I'm waiting this spring to see how it responded to being moved last fall. If it survives, no, if it thrives, then I'll be sending plants out to several growers to see how it does in other gardens. It has many marks of a new and desirable hybrid, and the flowers are nicely complex, with a delicate turquoise flush, golden yellow signal and reddish veins, an open and upright flower, a sturdy base of leaves and strong shoots. The current test is to see how it transplants; desirable PCI seedlings often fail at this test.

This seedling PCI last year had lovely flowers with golden signals, reddish veins and a turquoise flush on the falls. This year, I dug it up, divided it, and moved it. Will it thrive? We'll know in a few months. Photo by Kathleen Sayce. 

Choosing when to divide and transplant PCI can be funny to watch from outside the garden. The gardener pulls soil and mulch away from the base of the plant, looks closely, shakes her head, pats the materials back in place, then moves over to check the next plant, then the next... then goes away for a few days or a week. Or two weeks. Or a month. We are looking each time for that clear sign of a growing PCI–-live white roots on the base of the leafy shoots. Live roots grow twice a year, in spring and fall. In cool moist climates, new roots can grow for several months, almost year round, while in climates with prolonged dry summers, they might grow for only a few weeks: 6-8 at most in fall and spring, with cold weather slowing growth midwinter, and dryness slowing growth midsummer.

Fall is a good time to transplant PCI. These plants have sturdy shoots with white roots on the current year's fan. The new fans are visible as tiny sprouts above the roots, on the left side of both transplants. These transplants are from a vigorous yellow-flowered I. douglasiana selection. Photo by Kathleen Sayce

Why this spring and fall root growth pattern? PCI are native to the West Coast of North America, which has a Mediterranean-type climate. This means that there is a brief to very prolonged dry season each summer, depending on latitude, when PCI go summer dormant. When rains return in the fall, they produce tiny new fans of leaves with tiny buds of roots; and older roots just behind them, on the current year's fan, start growing again. The new fans elongate in late winter and spring, and shoots emerge to bloom in early spring to early summer, depending on latitude and climate. In late spring to summer, PCI set seed, and go dormant for the balance of the summer season. They awaken in fall with the onset of cooler temperatures and rain, producing new roots and tiny new fans.

Nurseries know this, and depending on where each is located, aim to ship plants when their roots are growing strongly. This is most often in the fall. For gardeners accustomed to shopping for new flowers by seeing flowering plants at a nursery, and taking them home, this delay can be frustratingly long.

Patience is everything in a garden. Growing PCI is a study in patience. You see the plant. You find a nursery that sells that plant, and place an order. You wait. That fall, or the next, it arrives, and you plant it, and you wait. Perhaps it dies––these are PCI we are discussing, after all. So you try again. When it flowers, you see that it's the plant you sought. Or not. And you try again.  But what a reward with success.