Fall: Caring for Your Native Plants Garden

Fall Gardening Tasks

• Divide spring-blooming perennials
• Plant spring ephemerals
• Plant trees and shrubs
• Maintain perennials
  • Retain seed heads
  • Cut seed heads back
  • Collect seeds
• Leave the leaves

• Fall can be a good time to propagate perennials that bloom from spring to mid-June as this gives the plants time to establish roots before winter weather sets in.

• For clumping plants, such as Allegheny Spurge, Bellwort and Blue Vervain, gardeners can dig up the clumps and use their hands to gently pull apart the roots into smaller sections, making sure each has viable shoots. A garden knife can be used to slice apart large, dense root balls. Sections should be immediately replanted and watered.

• Mayapple, Virginia Bluebells,  and Wild Ginger grow from rhizomes which can be cut into pieces with a sharp, sterile knife, making sure each has one growth point (node) and roots. Pieces can be replanted at the original depth with the node facing up.

• Native irises can be divided in the early fall when their leaves begin to yellow. Entire clumps of rhizomes can be lifted from the soil with a spade and pulled apart, retaining healthy roots and one or two leaf fans.
• Large, old rhizomes which have no fans, or which are soft and smelly, should be discarded.
• Irises should be replanted with the top surface of rhizomes just visible at the soil surface. Soil should be tamped firmly around the roots. The newly planted rhizomes should be watered but not mulched as that can lead to rotting.
• Refer to the table Dividing Native Perennials for details on other plants.

• Fall is also a good time to plant spring ephemerals, such as Spring Beauty, Virginia Bluebells, Mayapple, or the trilliums, which are dormant at this time of year.
• It is best to plant them from either corms or rhizomes because it can be challenging to grow these plants from seed, and they may take up to seven years before they will flower.
• It’s a good idea to use markers to help locate plants again in the spring and to plan for other species, such as ferns or ground covers, to fill the blank spots after the ephemerals die back in the summer.
• See the recorded presentation on Native Spring Ephemerals for more details on these plants.

• Fall is the ideal time to install woody plants. Warm soil, cool air temperatures, and increased rainfall in this season help trees and shrubs establish healthy root systems before the ground freezes.
• While it can be tempting to plant large specimens, foresters recommend that younger plants are more likely to establish successfully.
• General tips for proper planting include:
  • Digging a shallow planting hole 2-3 times width of root ball
  • Carefully spreading out the roots
  • Placing the root flare (where roots attach to the trunk) just above ground level
  • Filling the hole with unamended soil to encourage the roots to grow beyond the hole into the surrounding soil.

• For more planting details based on the root type of the plant  (containerized, balled-and-burlapped, bare root), see this fact sheet on How To Plant a Shrub or Tree .
• A final step in planting is to provide proper mulching with shredded bark mulch or arborist’s chips. These materials should be applied only two to three inches deep, ideally all the way to the drip line (outer edges of the branches).
• The mulch should ring the tree rather like a donut, keeping clear space of at least 6 inches all around the trunk to prevent moisture retention and rotting.

• One reason to consider cutting back at least some seedheads is to control the spread of self-seeding plants in the garden. Examples include plants in the Rudbeckia genus, asters, and goldenrods.
• Gardeners may also want to cut back the seedheads in public-facing beds to give a tidy appearance. Seedheads of plants such as Sundrops, Beardtongue, or Lyreleaf Sage can be cut back to their attractive evergreen rosettes, allowing them to serve as winter-hardy ground covers.

• A third reason to cut back some seedheads is to collect seeds for propagation purposes. This can be a way acquire additional plants inexpensively or to share them with friends and neighbors.
• Refer to helpful guidelines from the Lady Bird Johnson Wildflower Center, the Xerces Society, Plant NoVA Natives, and Missouri Botanical Garden:
  • How to Collect and Store Seeds
  • Collecting and Using Your Own Wildflower Seed
  • Native Seed Propagation Methods
  • Growing from seed
• The last source includes a video on “Winter Seed Sowing” by two expert propagators from the Virginia Native Plant Society.
• Consult a spreadsheet of seed germination guidelines for details on many native plant species.

Images from “Winter Seed Sowing,” Northern Virginia Bird Alliance

• A final consideration for autumn garden care is deciding how to handle fallen leaves. For forested parts of the yard, the most sustainable practice is to allow leaves to overwinter in place.
• Not only does this approach save time and money but it results in a natural recycling of nutrients. The gradual decay of leaves builds organic matter in the soil while providing a protective covering that prevents erosion.
• In addition, a layer of leaf litter provides important protection for overwintering bumble queens and the larval stages of butterflies, moths, and fireflies.
• See a recorded presentation “Exploring the Effects of Leaf Litter Removal on Insect Communities” for important information on delaying spring clean-up of leaves.

• Another beneficial use of leaves involves placing them whole or shredded as a mulch under lawn trees and foundation shrubs and in flower beds. Care should just be taken to keep leaves from piling up against the trunks of any woody plants and to avoid smothering the evergreen basal rosettes of herbaceous species.
• Gardeners can also run a mower over leaves on any lawn areas as a nutrient supplement or can add them as the “brown” or carbon component in making compost.
• See the recorded presentation “Leave the Leaves and Other Beneficial Practices” for more details.