Creating a beautiful, functioning landscape depends on putting the right plant in the right place at the right time. Iowa State University Extension horticulturists describe the correct plants and care to give late summer and early fall plantings. To have additional questions answered, contact the experts at firstname.lastname@example.org or call 515-294-3108.
Late summer and fall is an excellent time to plant balled and burlapped and container-grown trees and shrubs. Evergreens should be planted by early October in Iowa. Evergreens retain their foliage (needles) through winter. Evegreens need adequate time to get established at their new site before the onset of winter to prevent desiccation injury. Deciduous trees and shrubs drop their leaves in fall and go dormant. Deciduous trees and shrubs can be planted up to mid- to late November.
Late summer and fall planted trees and shrubs should be watered on a regular basis during the remainder of the year. Periodically check the moisture status of the plant’s root-ball. Water newly planted trees and shrubs when their root-balls begin to dry out. Continue watering until the ground freezes in winter.
Late summer (mid-August to mid-September) is the best time to seed new lawns and overseed existing lawns. Late summer planting has several advantages over spring seeding. The seeds of cool-season grasses germinate quickly in the warm soil of late summer. The warm days and cool nights of early fall promote rapid turfgrass growth. The growing grass also has less competition from weeds as few weed seeds germinate in the fall.
After seeding, keep the upper 1 inch of soil moist with frequent, light applications of water. Most turfgrasses should germinate in two to three weeks if the seedbed is kept uniformly moist. Gradually reduce the frequency of watering, but water more deeply, when the turfgrass reaches a height of 1 to 2 inches. Mow the grass when it reaches the height of 3 to 3 ½ inches.
Late summer and early fall is an excellent time to plant many perennials. It also is a good time to move or divide perennials, such as peony, daylily, garden phlox and oriental poppy. Perennials planted in late summer or early fall should be mulched with 4 to 6 inches of straw, pine needles or other materials in late fall. Mulching helps prevent repeated freezing and thawing of the soil that can heave plants out of the ground. Plants heaved out of the soil may be severely damaged or destroyed due to the drying of the exposed plant crowns and roots.
Unfortunately, fall planted garden mums usually don’t survive the winter even when given winter protection. Flowering mums purchased in late summer or early fall should be regarded as temporary additions to the landscape. Spring is the best time to plant mums in Iowa. Spring planted mums have the entire growing season to get established and usually survive the winter much better than those planted in fall.
Peonies are available as potted and bare root plants. Potted peonies are often available at garden centers and can be planted anytime during the growing season. Bare root peonies are best planted in late summer/early fall (September in Iowa). When planting bare root peonies, position the “eyes” (buds) 1 to 2 inches below the soil surface.