What is the best month to split perennials ? What is the best time of year to transplant perennials ? I live in northern Illinois. Mary G.
Splitting and or transplanting
I do it in the Spring when things are just popping up, or in the Fall...when done in the Fall just make sure they have time enough to establish their roots before a freeze.
I divide spring blooming perennials after they bloom and the same with fall blooming perennials.
I prefer spring, it gives the divisions a chance to make roots .
Dividing
Spring is probably the best time to divide most perennials. However, with care, it can be done most of the growing season. Never divide in the middle of winter (I speak from experience). If you have mister (one of the patio cooling types works just fine) you can put it on the freshly divided perennial for a week and have 100% success in the middle of summer assuming temperatures are reasonable.
Transplanting
If weather is cool (below 75 degrees for the daily high) and the plant is small enough to dig a root ball as big as the plant itself, you can move it any time. If the perennial is enormous it should be cut down to the size of the root ball when transplanted. Some perennials like baptisia, lupine, and rhubarb that have tap roots do not transplant well, so spring is best. However it will severely set back the growth of that plant for the year, and may even eliminate that year's bloom.
Since we had a freeze here last night, I'd be leery of dividing plants. If you really have to transplant something now, I'd get as big a dirt ball as possible and move it fast, water, and mulch it. Maybe we'll get some warm days after this obnoxious cold we're getting so early.
In general, I divide Fall and Summer blooming perennials in the Spring and Spring Bloomers in the Fall. Iris are best divided 1-2 months after they bloom which usually means July for me. Not my favorite time to divide. Daylilies seem to do fine divided about anytime of the year.
Susan
This message was edited Dec 18, 2009 7:00 AM
I agree with Susan 100% - even the awful time to divide iris in the midst of July.
So, you would divide Hostas in the spring then?
After bloom. I'd divide in September/October and they'd have the chance to develop new roots and bloom again the following year.
Hostas are incredibly tough, and can be divided any time the ground isn't frozen, even in the middle of the summer. The only disadvantage to dividing them when they are in full foliage is that they look "unbalanced" until the following year; the usual perfect symmetry is ruined. I prefer to divide mine in early spring, just when they are breaking dormancy or early fall, just as they are beginning to fade.
Thanks for that!
As a general rule, I divide perennials as others have suggested above, but you do run into the occasional plant that is more particular about timing. Specifically, Pulmonaria comes to mind. When divided in spring, just after blooming, they bounce back quickly, however one year I was anxious to increase them and divided them in fall- big mistake! They barely made it, but were still pathetic looking the next spring. Later I found some info about them that noted to only divide early in the growing season.
Didn't know that about lungworts.... and am glad for the info as I have some larger plants that need dividing. Thanks.
Thanks, Neal. That saves those of us who have them some grief.
It was such a bummer that year I divided the lungworts in the fall, they had done so well that summer and produced so many dividable side shoots I was anxious to create a large drift of them. Only the next spring to have pitiful foliage and few blooms on the survivors. Experiences like that sure do stay with ya, LOL!
But now you have tons, yes?
Well, sadly, no. That was in my last garden, when I lived in a moist, woodland environment. I did bring some here, but they weren't as vigorous in this dryer, more open environment. Then last fall we had backhoe work done that got started several days before I was told it would, and the lungworts I did have were casualties of that destruction. I had found pieces of the clump afterword, and replanted them, but it was late November, and none survived.
Well, Neal, you did save some of us who might have made your mistake so a big thank you from me to you.
Aw, poor guy. But, looking in my green crystal ball, I see some tall, speckled lungworts in your future ....
That's the beauty of DG, being able to share those mishaps, and hopefully help others avoid them. As well as the bountiful successes!
Pagancat, oooohhh! I would love to see your "vision" come true ;-) I had actually forgotten about the Pulmonarias, and this thread reminded me. Although I'm sure come spring, seeing the species tulips that echo the colors (in reverse) of the immature and mature lungwort blooms would have reminded me.
Uh huh - but you get the 15% off of Bluestone's Pulmonarias only until Jan 20th .... unless, of course, you have a better source, hmm?
And those kinds of visions *always* come true!