Yes you can plant before winter sets in. Late August and early September, about 4 to 6 weeks before the first hard frost occurs in zone 4, is actually the best time to get many perennials, hardy seeds, shrubs and trees into the ground. You will also be taking advantage of the end of summer sales at the garden centres and the plants will have time to get a healthy head start on spring. They go into warm soil at a time when there is usually more even rainfall and low evaporation and roots will continue growing even after above ground foliage becomes dormant. This is also the perfect time to reseed your lawn or lay new sod. Late August is the perfect time to plant cool weather fast growing vegetable seeds for harvesting before frost.
For perennials, dig a hole three times as wide and as deep as the root ball and place a handful of cured compost or root promoter in the planting hole. Place the plant in the hole, teasing apart some roots from the root ball. Fill in with soil to slightly above the level at which the soil was in the container. Tamp the soil and water well. Shear back by half late blooming perennials to promote root growth rather than bud and flower growth. Add a 7-10 cm layer of mulch or shredded leaves placed 5 cm away from the plant stem. This will keep the soil warm and prevent frost heave. Water as necessary up until the ground freezes.
A List of Suggested Plantings for Late Summer and Fall:
Flower Seeds: larkspur, pansy, snapdragon, spider plant, sweet pea, plus other seeds listed in seed catalogues as ‘hardy’ annuals
Vegetable seeds: baby carrot, lettuce, Mesclun mix, radish for fall harvest, chives for spring harvest, and garlic cloves for next summer’s harvest
Bulbs: deer and rodent resistant bulbs such as camassia, daffodil, glory of the snow, scilla, blue and striped squill
Perennials: aster, astilbe, bergenia, Chrysanthemum x grandiflorum, daisy, hens and chicks, hosta, Japanese anemone, lady’s mantle, oriental poppy, peony, pinks, viburnum
Grass Seed or Sod: standard types of mixes suitable for zone 4
Shrubs: ninebark, blueberry and other shrubs hardy to zone 4 with some exceptions*
Trees: catalpa, cork tree, crabapple, hawthorn, horse chestnut, linden, maples hardy to zone 4, pine, spruce
*Plant in Spring: Christmas and Lenten rose, gas plant, rhododendron and azalea hardy to zone 4, birch, fir, hemlock, hornbeam, magnolia, oak, willow, yew
A PDF file can be downloaded below
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