Established irises usually resist freeze-thaw cycles handily, but newly planted seedlings and late-transplanted adult cultivars are vulnerable, especially if the winter is very wet. It can take months for the dirt in newly planted beds to settle and compact. During this time, the sun, Jack Frost and the rain can combine to coax the plants up to where their roots are exposed, to be cooked by the sun. A good precaution is to cover those vulnerable beds with 1-2 inches of finely shredded wood mulch just after the first hard freeze of the winter. What the mulch does is provide a sort of insulating blanket over the roots, absorbing/deflecting the winter sun, tending to keep the temperature below the mulch more even during the 24-hour cycle, and shielding the roots from direct rainfall. You'll have to remove this mulch in spring, of course, but you'll have saved your plants.
Pot your plants upon receipt in July or August so they can develop a root ball in the pot. Unpot the entire ball of wax in October. Started this way, newly acquired irises are not likely to heave. If you have left-over bricks from recent construction or have access to bricks, place one over the rhizome.
ReplyDeleteWalter Moores
I've found that using bricks causes me to lose some varities. I think the bricks absorb moisture and thus leads to rot. I know make hooks out of wire and anchor the rhizomes that way.
Delete