Autumn is the
time for planting almost all broadleaf deciduous trees and shrubs, needle bearing evergreen trees and shrubs, as well as flowering bulbs, hostas,
iris, peonies, daylilies, yuccas and other hardy perennials. This is so because a series of conditions converge that sets the stage for a unique growing environment that not only greatly diminishes the possibly of transplant shock, but also allows plants to use their energy in ways that other seasons simply don't.
In the fall, throughout Washoe Valley and many neighboring areas, the soil is still warm while water evaporation rates have slowed and the air temperatures have cooled down considerably from the intense August highs. This unique type of climate allows plants to root quickly without the typical stress associated with the searing summer heat of our high desert region.
The way this works is that for most plants the above-ground growing season is more or less over by early autumn, and yet, since the soil is still warm, such plants will typically redirect their energy from leaf growth to root development. In other words, we could say that since next year's growth depends upon the ability to find moisture, and since such an ability depends upon a root system large enough and healthy enough to support such growth, plants "look to the future" in the fall by taking advantage of the warm soil, the lingering moisture, and the fact that foliage production has been suspended until the distant spring. And since this is what plants normally or naturally do in the fall, transplanting your plants at this time allows them to adjust to their new home at a time which is normal for the type of growth (root growth) needed for adjustment. In this way, plants get a considerable head start -- some say even a year's worth of growth -- over both spring and summer planting.
Fall planting is better than springtime planting because when we plant in the spring, plants will often simply sit there waiting for the soil to warm before attempting to establish their proper root depth. This delay can impact upon spring and summer growth since the plant's energy will have been more severely divided between above- and below-ground activities. If the plant had been planted in the autumn, the root growth needed for this year's growing season would already be in place, thus allowing the plant to direct more of its energy toward stem, leaf and flower production.
Fall planting is much better than summer planting because the autumn air temperatures protect plants from the severe set-back associated with the stress of hot weather transplant shock. When we plant during July and August, plants are forced to divide their energy between above-ground and below-ground activities at a time when evaporation rates are at their zenith. During the hottest part of the growing season, plants typically need more water to survive anyway, but this need is compounded if the plant has not had time to adequately integrate its root ball with the surrounding soil. In other words, when we plant during the heat of the summer, we must be ever more mindful of the plant's needs. That is, we must over-compensate for the plant's lack of time to integrate itself with the surrounding terrain by watering more often, at least until the plant can catch up with what would have already been established if the plant had been planted in the fall.
For perennial seeds that need to be chilled in order to germinate (many grasses and wildflowers need chilling), it is good to plant (or scatter) the seeds just before the first snowfall, usually around the end of October. The timing is right for at least two reasons:
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