October in the Ornamental Garden

Most of the chores on your September to-do list still apply in October – weeding, deadheading, dividing and transplanting perennials, planting new trees and shrubs, weeding, and more.   Start your list by checking the  PMG/Monthly Gardening Tips/October located in the Gardening Resources section of this website.

Plant spring-flowering bulbs during the first half of this month; it’s best to get this done by one month before the first hard freeze.  The cooling temperatures of fall are good because they encourage root growth at the base of the bulb and prepare it for a good start come spring.  But if temperatures are too cold, the root and shoot growth of the bulb can be adversely affected.  So when’s the ideal time to plant?  When nightime temperatures are staying in the 40°–50°F range.  How might this advice be impacted by climate change?  That’s uncertain, but let’s all start noting our observations.

If you’re not sure which bulbs to plant or how to do it, check out Spring-Flowering Bulbs/The Garden Shed. For a list of deer-resistant bulbs, see Mich.State Ext. The narcissus or daffodil is a favorite for good reasons; not only is it unbothered by deer or other pests, your cache of bulbs expands and spreads wonderfully.

Fall is the ideal time to plant or transplant most shrubs and trees, though it’s NOT the ideal time for planting broadleaf evergreens. But mountain laurel, boxwood, and hollies CAN be planted in the early fall if they are kept moist and mulched.  If you’d like to add a flowering tree, consider the options discussed in this new publication from Virginia Cooperative Extension:  Selecting Landscape Plants: Flowering Trees.  For guidance on choosing the right tree for your yard, take a look at one of these websites:

• Virginia Native Plant Finder  (an interactive site that allows you to plug in variables)
• Right Tree-Right Place Tree List/Tree Stewards (comprehensive and local)
• Piedmont Natives Plant Database/Albemarle County.org  (searchable)

You can continue to divide perennials that bloom in spring or early summer — at least during the first half of this month.  After that, watch weather forecasts closely since you should complete this job by four to six weeks before the ground freezes.  For expert guidance, see this recent Garden Shed article:  Guidelines for Dividing Perennials.

Cut back perennials with disease or insect pest problems to reduce the chance of infection the following season. Bee balm (Monarda) and phlox (Phlox paniculata) with powdery mildew are examples. Remember to destroy — not compost — diseased stems and leaves.

October is NOT the time to prune for most shrubs and trees except to remove dead limbs.  There are exceptions to every rule; to be sure about the best time to prune your particular shrub or tree, look it up on the Pruning Calendar contained in When to Prune/The Garden Shed.

After the first killing frost, you’ll want to cut back most browning perennial foliage, but leave some seed heads for those you want to self-seed or to provide food for wildlife. During the winter, when food is scarce, seed-eating birds, such as finches, sparrows, and chickadees, will dine on the seed heads of Echinacea, Rudbeckia, Helianthus, Coreopsis, lavender, Russian sage, thistles, and grasses. Be sure to cut back hostas and remove all their leaves from the ground as soon as the frost takes them; dead hosta leaves harbor slug eggs.

Leave seed heads in place for annuals or perennials that you want to self-seed; alternatively, you can wait for the seeds to mature and scatter them now in the areas where you hope to see them next spring.  Some annuals and biennials that reseed themselves include cleome, cockscomb, cosmos, foxglove, hollyhock, larkspur, money plant, sweet William, forget-me-not, Shirley poppy, zinnia, four-o-clock, marigold, and impatiens.

Certain plants do not like to be cut to the ground before winter because the foliage protects their crowns. Plants that like some winter foliage protection include: butterfly weed (Asclepias tuberosa), chrysanthemums, coral bells (Heuchera sanguinea), Siberian bugloss (Brunnera macrophylla), Salvia x sylvestris, lungwort (Pulmonaria), bearded penstemon (Penstemon barbatus), catmint (Nepeta), and Shasta daisy (Leucanthemum x superbum). If a perennial is growing new basal leaves, cut off the spent stalks, but don’t disturb the base.

This is a good time to attack the invasive autumn olive and oriental bittersweet.  Bittersweet leaves tend to remain green in fall after most other plants have changed color or dropped their leaves, so infestations are easy to spot. Also, as autumn proceeds the berries on bittersweet vines become more noticeable as they change from golden to red.  Another factor working in your favor is that in fall, sap is moving down toward the roots, so the cut-stump method works well.  To use the cut-stump method, you’ll need a concentrated form of herbicide to paint onto the stems right after you cut them —  as close to the ground as possible, as shown in the photos below (and yes, there is poison ivy in that bed of invasives, along with the bittersweet). There are ready-to-use stump-killer products on the market.  For details on the cut-stump method, see Controlling Invasive Plants Effectively & Safely with Herbicides/Blue Ridge Prism.org and Non-Native Invasive Plant Species Control Treatments/Va. Dept.Forestry.

 

 

 

 

 

 

 

 

 

 

Eliminate invasive tree-of-heaven (Ailanthus altissima) to help combat spotted lanternfly, which was recently sighted in our area.  It turns out that tree-of-heaven is the favorite plant of spottted lanternflies.

Ready your indoor holiday bloomers for the holidays.  By manipulating the amount of light they receive, you can control their bloom schedule. Such plants include:  Christmas cactus, kalanchoe, amaryllis, and poinsettia. For specific instructions, refer to  “The Ornamental Garden in October,” The Garden Shed, Oct. 2016.

Does your lawn need a renovation due to the summer drought?  For help in answering that question and guidance if renovation is needed, see this new article, Cool Season Lawn Renovation, Va.Cooperative Extension (2021).

SOURCES:

Featured Image:   Pink Muhly grass (Muhlenbergia capillaris). Photo courtesy of Missouri Botanical Garden PlantFinder, Mo.Botanical Garden Plantfinder/Muhlenbergia capillaris

“Where are my bulbs?  Why aren’t they flowering?” Michigan St.Univ. Ext

Blue Ridge Prism Invasive Fact Sheets

“Planting a Tree or Shrub,” Univ.of Maryland Ext