I'm not really a 'northern' gardener, but I'll stick my 2 cents in anyway.

I think it would be hard to develop a fixed rule of thumb for this. The growth rate of any plant depends on so many variables; variety, climate, microclimate, etc., that virtually every plant in your garden will be different, and they will be different each year.

Example; I have 2 clumps of Blue Fescue, both started from the same seed in Spring '04, and planted out side-by-side at the same time. They grew equally until this summer's dry spell. One died out in the middle, and the other did not. I'll divide the one that died out, and move the other, leaving two equally sized plants in the original location.

I haven't read Harper. What's her reasoning for nicking one side of a grass each year? It seems like one effect would be to move the plant in the direction opposite the side you nicked, but how does it rejuvenate it?

Donn, thank you.

I think Harpers reasoning is to reduce the plant each year. I suppose if you amend the soil it would stimulate growth to that area.

I am mainly concerned with Miscanthus, as that seems to be the most popular plant I sell. Do you (or anyone else that can answer this) have any larger Miscanthus, and how long have you left them alone. At what year do they seem to look their best, and when do they seem to go downhill.

I'm not looking for anything set, just a general idea of what people are doing.

I'm wondering if some people never divide at all.

I would be very interested in hearing from anyone about this, please.

And thank you again Donn, as always.

Polly

I'm a northern gardner: zone 5a in western Catskills with a relatively short growing season, and I grow seven or eight (who counts) Miscanthus cultivars. I divide only when I must, as determined by size (whether or not plant has outgrown its spot) or performance (excessive floppiness and/or dying out in the center, which often go hand-in-hand).

I do not see value in Ms Harper's advice to divide yearly other than for propagation. Otherwise, why bother? In my experience, it is better to wait until their centers die before dividing. (There are many reponses in this forum dealing with "how" to divide, so I won't go into that much.) Taking a chunk of a plant from just one side is something I don't recommend, because the plant is apt to grow lopsidedly.

Center die-back is a natural habit of grasses (from their first year) and becomes noticeable in most M. sinensis cultivars after about three years. But that does not mean they must be divided that frequently. (Early die-back that is apparent in Spring may not be so at summer's end, as they are apt to "fill-in.") Usually five to seven years of growth will necessitate division, or once a plant's overall width noticeably exceeds the height of its foliage. A rule of thumb for most sinensis cultivars: the bigger the plant the longer before it must be divided; M.s. "Adagio" or M. "Purpurescens" about every four to five years. This coming spring I will divide a M.s. 'Variegatus' in its seventh year; and a M. "Purpurescens" in its sixth year (I should have divided the latter last spring.)

Waiting so long to divide, means that the plant is more easily divided while it is in the ground (in Spring before or as new growth begins). Be sure, though, to remove all of the plant's dead center to prevent lopsided growth. Have new beds prepared or line up many willing recipients (or buyers).

Don, thank you! That was extremely helpful.

I try to explain to my customers about the dieback in the center, and flopping as a sign of needing division, but I'm often asked how many years. I think your 5-7 sounds proper, and I did not realize that the size of the cultivar would be an indicator of how often to divide. I sell many Miscanthus cultivars, many large. That's what seems to be popular for my customers.

Regarding Ms. Harpers book, it just brought the question to mind. Ms. Harper gardens in warm Virginia on sandy soil, and I assume she has a much faster growth rate than I. So division every three years may be necessary for her, although I did not understand the taking of 1/3 of the plant per year, either.

Thank you again, very informative.

Polly