With colder weather approaching, it’s tempting just to let Mother Nature put an end to your gardening season. But if you take the time to properly put your garden beds to rest, you’ll have better results next spring and summer.

Bob Hedlund, perennials manager at Tonkadale Greenhouse, suggests that you start putting your garden to bed when the temperatures consistently drop into the low 50s and 40s. As you watch the weather, evaluate your garden design. Add, move and divide perennials at this time to provide color and interest throughout your bed.

Division is a useful technique to help keep your perennial border healthy and neat. Cut or pull apart the root clumps, leaving two or three new shoots per segment. Plant the new divisions at the same depth as the old plant, water thoroughly, and keep the soil moist for several weeks. Good fall candidates include Asiatic lily, bearded iris, day lily, Jacob’s ladder, peony, tall phlox and Siberian iris.

Final fertilizing should be completed by the end of July or the first week in August in zone 4, which covers Minneapolis. Top dress your beds with manure after first frost, Bob suggests.

Let some of your plants stand over the winter. Many varieties provide beautiful winter interest because of the seed pods, berries or dried stems. They also provide food for the birds, shelter for critters and a place for pollinators to overwinter as well. Some gather snow, which insulates the garden from extremes in temperatures and the damaging effects of freezing and thawing cycles.

Tonkadale Greenhouse hydrangeasGood plants to leave standing:

  • Perennial grasses
  • Bergenia
  • Coral Bells
  • Asters and mums
  • Shrubs, especially hydrangeas with their brilliantly dried blooms
  • Rudbeckia (black-eyed Susan)
  • Sedums
  • Echinacea (coneflower)
  • Achillea
  • Monarda (bee balm)

Five Golden Rules for Fall Gardening

Bob has Five Golden Rules for Fall Gardening.

1) Feed the soil after the first hard frost. Here are some suggestions on enriching your garden soil:
https://tonkadale.com/enrich-soil-to-grow-healthier-plants/

2) Mulch your beds. Winter mulching:

  • Protects plants from the drastic temperature changes in the soil that arise from freezing and thawing.
  • Insulates plants from extreme cold.
  • Prevents soil erosion.

Mulch your perennial beds with 4-6 inches of mulch, dried leaves, shredded bark or marsh hay. Make sure whatever material you use is weed-free. If you’re covering peonies, do not cut down peony foliage until it is damaged by frost. Once the soil freezes, simply rake some leaves over the plants, then remove the mulch in spring.

Don’t mulch too early or you may encourage disease and pest problems or even promote your perennials to re-grow. Wait until after the first hard frost.

So what is really happening when you cover a plant for winter? “Sometimes the cold temperature is not what damages the plant, but rather the freeze/thaw cycle affecting the soil and causing it to ‘heave’ the plant,” says Jessie Jacobson, Tonkadale’s general manager. “Insulation works both ways. It can prevent the soil from cooling off too quickly, but it can also prevent it from warming up promptly when the time comes.”

When the seasons change, “be sure to remove that mulch in the spring before temperatures begin to warm up too high and either 1) mold begins to form or 2) it suppresses the perennial from growing,” Jessie says. “Frequently check for plant growth or mold to remove the mulch, but keep some on hand to temporarily add protection for a late frost.”

University of Minnesota Extension has more information about protecting trees and shrubs from winter damage.

3. Clean up your garden after the first hard frost. 

  • Remove weeds and unwanted annuals.
  • Remove dead and diseased foliage from shrubs and perennials.
  • Dig-up non-hardy bulbs such as cannas, dahlias and gladiolas, let them dry and store them in a cool, dry place.
  • Cutting back your perennials in the fall will eliminate cleanup in the spring and encourage fresh growth in the spring.

4. Water is essential for winter survival

Make sure to water trees, shrubs, and perennials throughout the fall (about 1 inch of water per week) until the first hard frost occurs. Summer drought can create stress for these plants in the dry winter months.

5. Plant spring blooming bulbs. Tonkadale has instructions on the best way to plant bulbs.

And don’t forget Bob’s final rule:

Relax and spend time in your fall garden.