fall planting

Many homeowners and neophyte gardeners think that the best time to install new plantings is in spring.  In fact, with enough care you can plant almost any time of year here in the Northwest except the dead of winter-- but fall is the very best time to plant or transplant shrubs, trees, and most perennials.  It is also the best time for starting many things from seed.

There are two reasons why fall works best for getting plants off to a good start.
1. Most importantly-- plants have a stronger start if they can develop robust root systems before putting on a lot of shoot growth.  Plants have a sort of energy budget-- more flowers mean less leaves, more shoots mean less roots.  In fall, plants are moving toward dormancy, beginning to slow down or shut down completely in shoot growth.  As long as temperatures remain mild, root growth will at the same time increase.
2. With cooler, wetter weather, soil moisture is more constant and transpiration (loss of moisture through leaves) is minimized.  So general stress and transplant shock are minimized. 

Here in the Puget Sound region, we can usually count on at least a month of mild temperatures if we plant sometime during September or (ideally) October.  The only plants we may want to get into the ground a little earlier (August or September) are those that are a bit tender.
Plant acquisition for fall installation is a good news/bad news situation:  many garden centers are offering sales, sometimes radical reductions in prices, for all plants.  On the other hand, inventory is likely to be limited, and availability of special orders will also be limited.

New fall plantings should be well-mulched, and if temperatures plunge close to freezing or below, extra protection may be called for.  Particularly for plants installed after the end of September, for the next couple of months you may wish to throw a tarp, blanket or Reemay covering over them when nights are expected to be very cold.