RE: CULT: How Late is too Late?

Because fall and winter vary so much from year to year, it's a gamble guessing when the first damaging frost or killing freeze will be.

Based on experience, I've learned that seedling transplants with baby rhizomes less than a quarter inch in diameter will have a hard time making it thru the winter without protection. Larger than an inch or so, they probably will make it unless they are especially intolerant of the up and down weather.

I try to guess with the smaller ones whether or not they will have time to grow enough before persistant cold (i.e., occasionally frozen soil) stops them.

For me, that seems to mean finishing planting smaller babies one or two months before first damaging frost, depending on what the weather is doing - if it's still in the 90s and dry, I will gamble and plant later. As we get closer to cold weather, the smallest size I will try planting gets bigger.

If seedlings or mature rhizomes don't have enough time to really get some good growth in before they are shut down by cold, I will either put water filled cola bottles around them as 'mulch' to absorb heat during the day and keep soil warmer at night, or cover with non-woven fabric plant bed covers (i.e., Reemay), or both. If it ever turns really cold in the winter here again, I will cover with Reemay and leave it there until spring.

I've experimented enough with both to know they can make a big difference in how well late transplants/purchases make it thru the winter. Also works for late/early spinach, lettuce, and tomatos.

Another useful indicator for me - are the winter weeds growing? If yes, then I figure soil temperature is also warm enough for iris roots to grow.

I've planted old dried up overlooked rhizomes as late as November here, but prefer no later than late September. Average first frost is Oct, first killing freeze can be anywhere from Oct to December, ground has frozen as early as November, usually after Christmas, only froze the surface of the soil one or two nights the last few years, then there was the year it got down to minus 25 F. ugh. If we have subzero weather this winter, I will probably try to mulch the smaller seedlings rather than count on Reemay or water bottles.

I hope some of those rambling thoughts are helpful!

My question was/is 30 days before your first freeze or 30 days before a hard
freeze? Down here there is a big difference between the two. Our first
freeze is traditionally on Halloween. However, our hard freeze is not until
late December, early January.
A lot of locals have planted their iris in December with little to no bad
effects. Has anyone done any research on this?

Dana D. Brown
Seems the minimum was 30 days of 45 degree soil temperature for good survival on Long Island. As the time period increased survival and prospering increased. ..... Of course this was with shrubs.
George Mason Portland, Oregon


it is all a
matter of how long those conditions which are essential to the transplants
getting down good roots will remain present in any given locale.
Anner Whitehead

Richmond VA USA


--
Linda Mann east Tennessee USA zone 7/8
East Tennessee Iris Society <http://www.korrnet.org/etis>
American Iris Society web site <http://www.irises.org>
talk archives: <http://www.hort.net/lists/iris-talk/>
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