A common summer question is when should I divide my perennials in the fall. If I sense that the questioner has the ability to smile my quick answer is August 20 at 2pm.

Usually I add the qualifier that if it is dry wait until the first fall rains start to arrive. That is not necessary this year.

You can divide any perennial now but the conventional wisdom is that if it has already bloomed do them now. If they are currently blooming or will bloom later wait until next April.

The exception to both rules in my mind is ornamental grasses who would respond best to division in late May.

Any time you transplant or divide one of your garden perennials you should reduce the leaf surface. Remove maybe a third to one half of the existing foliage. If you are transplanting a shrub a bit of pruning might be in order too.

I will admit that in recent years the above idea has been challenged by the researchers, especially with trees and shrubs. The new idea is that the transplant stressed plant needs every bit of green material possible to manufacture food to promote root development.

If you are looking to transplant a shrub or tree I would first determine whether it is evergreen (keeps its leaves all winter) or deciduous (looses it leaves).

If it is deciduous I would wait until at least some of the leaves have dropped naturally. Almost all deciduous plants have little risk of winter dehydration once their leaves have dropped.

With evergreens; whether it is a conifer, rhododendron, holly... you get the idea, I would move rather quickly to give the plant as much time as possible to reestablish its root system.

There is a real risk that evergreens could be damaged by dehydration given our normal temperatures and winds during the winter. March is especially a problem most years.

It would even make sense to offer some additional wind protection to first year evergreens. If the site is protected, or the transplanting occurred in the spring, the risk of course is much lower.

Everything I have said about dividing and transplanting applies to bring new plants to the garden in the fall. I've said it many times but will repeat it again.

Early fall is actually the best time to plant. The air temperature is dropping and the soil temperature remains high. With that you get more root development and less top development, That's just the formula for successful planting.

Since it was pouring rain at 2 pm August 20 I guess that we are all behind schedule. But don't despair. You still have plenty of time but no reason to delay.