Fool-Proof Fall Planting
As blazing summer heat retreats and the idea of being in the garden becomes appealing again (fun even?), a truly time-sensitive question arises. “Should I plant now or is it better to wait ‘til spring?” For those eager to “make their garden better” now, but are seeking a horticultural blessing, read this and go forth shovel in hand, confident you’ve made a sound decision.
- Gradually falling temps and autumn rains dramatically reduce stress for newly planted trees and shrubs. That translates into less time spent watering than spring planted trees and shrubs (what we collectively call woody plants).
- Shorter, more overcast days reduce the possibility of sunburn on large, soft-leaved plants, like Hydrangea (above) and Viburnum, for example.
- Even if deciduous plants have dropped their leaves and evergreens appear to be slumbering, as long as soil temperatures remain above 40° F. plants are producing new roots. Bear in mind soil temps drop much more slowly than air temps.
- Fall planted woodies are under no urging from Nature to produce new shoots, leaves and stems. Just roots, so these are plants that are getting established.
- Potential insect or disease issues that could be problematic going into summer are quite simply a nonissue in fall.
- Fall soils tends to be drier than spring. Always try to avoid planting in our heavy soils for a few days following a heavy rain. Digging in muddy clay soil can destroy structure, compact soil and affect future root development.
- For whatever reason, the roots of oaks and evergreens respond more positively to the warm soil temperatures of fall than the wet, slow-to-warm soils of spring.
- Rhododendrons (below) and evergreen Azaleas need to be well-established facing Old Man Winter. Typical winters dictate these broadleaf evergreens should be settled in their new homes by mid-October.
- The overwhelming majority of perennials thrive with fall planting. The later you plant the more imperative it is to mulch after the ground freezes, thus reducing the chances of “frost heaving” that often accompanies the freeze/thaw cycles of up-and-down winter temps. If you’re transplanting Peonies, Siberian Iris and Oriental Poppies, they MUST be moved in fall. There’s really no debate on those three plants.
P.S.- Love, love, love leaf mulch or cotton bur compost for mulching perennials.
- One of the admittedly few gardening advantages of the Upper Midwest is the miracle and beauty of spring flowering bulbs. Take that, smug gardeners in milder climates that scoff at our “limited” palette of plants. We can have tulips, daffodils, hyacinths, crocus and the charm of “minor” bulbs without having to refrigerate them.
I always like to buy bulbs early for best selection and store them in a cool, dry location. Restrain your fervor to plant until soil temperatures are consistently in the mid-50s. If you’re among the gardening majority that don’t have a spare soil thermometer lying around, wait for either of these two phenomena before planting: the first hard frost (one that kills tender annuals and veggies) or the deciduous trees and shrubs are showing considerable fall color and leaves are dropping.
- All this being said, there are a few widely accepted exceptions to the fall-is-great-for-planting rule. Whether it’s because of root structure or because we’re pushing the northern limits of a plant’s hardiness, in a typical fall we like the following to be in the ground no later than mid-October: any Birch, Japanese Maple, Magnolia, ornamental (non-fruiting) Cherry and Pear, and Redbud.
And, of course, who doesn’t like planting better when the temps and humidity are both low? Let’s face it, fall planting is full of advantages and pretty much fool-proof!
Chief Horticultural Officer