November: Care for the Perennials
Everyday I hear someone say, “I wish it was summer."
As much as I like to wear flip flops and T-shirts, I look at fall and winter as a vacation from yard work and a time to rest and reflect on the past year’s successes and ponder the rebirth of spring.
Like us, our gardens need time to rest and refuel to impress us once again with their beauty and wonder.
(But check out the stunning reblooming iris that's still going strong behind the Caleb Mills House.)
There is a large amount of information about preparing your garden for winter. Many people will simply strip the plants clean to the crown at the soil level. This is effective for easy clean up throughout the fall, but it isn’t ideal for plant health.
Exposed soil will generally freeze 10 times faster than soils that are covered with plant material, leaves, mulch, etc. Long term freezing of plant roots will increase the chance of plant death.
If you have shrubs and perennials in flower pots and plan on leaving them over winter outside, don’t be surprised to find many of them dead by spring. Roots of plants are still alive through winter, but when frozen solid, they are unable to take up water and oxygen.
I would suggest healing them in the ground, and apply a generous amount of mulch around. The plants should be good to go in the spring.
As a general rule, it is good to leave as much of the plant foliage as possible over winter.
There will be exceptions. If you have had disease or insect problems with a particular plant, you need to remove as much of the dead foliage as possible. Many insects and fungal diseases carry over winter in leaves and twigs, like apple scab. Don’t put this plant material in your composting pile — dispose of it off the property or burn it.
Mulching leaves into the lawn is fine as long as it is not excessive. Once the leaves pile up to the point that sun light cannot reach the grass plant, your yard will yellow and die. I compost all the leaves on campus and it takes two years to break down into fine compost.
If you are expecting the leaves to decompose by spring, it isn’t going to happen.
I leave you with a short list of plants that need special attention before winter:
• Hardy mums – leave all foliage until April 1, add some leaf cover to prevent cold damage. But don't expect all of them to come back — they aren’t that hardy.
• Ornamental Grass – Leave foliage until the end of March, then cut back to 6 to 8 inches above the ground (centers can freeze out).
• Semi evergreen perennials (Hellebores, liriope, Ivy) — Do not cut back in the fall. Cut them back only after they have turned brown, around the first first of April if needed.
• Broadleaf evergreen shrubs — These can burn in the winter if not protected. Consider protective wax sprays, burlap, etc. for boxwoods, azaleas, Rhododendrons, and Hollies.
• Butterfly bush — Cut back to 12 inches above ground before winter, and add leaves or burlap around the base to protect. These bushes can freeze down through the stems in the winter.
This butterfly bush is still blooming at the end of October. To prepare it for winter, cut back the stems to about 12 inches (see pictures below), then nestle leaves or burlap around the roots.
The semi-evergreen perennials shown below should be left alone. They provide nice color through the fall and winter. Cutting them off could also allow water to freeze deeply in the roots and kill them over a hard winter. Just leave them alone and enjoy their winter beauty.
Finally, for plants like hosta (shown at left), after you've trimmed back the bloomscapes, allow the foliage to die back naturally. The dead leaves will provide a helpful winter insulation. Just clear the dead material off the plant in the spring when we're out of danger of a hard freeze.