The Ornamental Garden in October
I consider October to be the “Countdown Month.” Although some chores can be pushed off to November, I work with one eye on the calendar, one eye on the first frost date, and one eye on the accelerating rush of leaves to the ground.
What tasks should move to the must-do side of our October maintenance lists?
MUST DO TASKS
- Cut back perennials. Refer to the October 2015 article, “Tasks and Tips in the Ornamental Garden” for a list of perennials that should be cut back and a list of perennials that should NOT be cut back.
- Dig up canna lily, caladium, dahlia, tuberous begonia, shamrock (Oxalis), and elephant ear (Colocasia) after the tops are browned by frost. Allow to dry; clean off soil; and store in peat moss or vermiculite in a cool location free from frost.
- Continue to plant spring-flowering bulbs until the ground freezes. Bulbs do best if planted about one month before the first freeze. In our area, there’s a 50% chance of first hard frost (32 degrees) by October 31; a 10% chance by October 13; and a 90% chance by November 18.
- DO NOT PRUNE trees or shrubs unless you are removing dead limbs. You might mistakenly prune off buds that have already set for spring bloom, or you could encourage a late-season blush of growth just when a plant should be getting ready for dormancy.
- Take in any houseplants that still remain outside before nighttime temperatures fall below the mid-50s. Wipe the pots clean of dirt and debris; spray off the plants; and check carefully for any insects.
- Start conditioning photoperiodic plants now for rebloom around the holidays. Photoperiodic means they react in a certain way to the daily cycles of daylight and darkness. By manipulating the amount of light they receive, you can control their bloom schedule. Such plants include: amaryllis, Christmas cactus, kalanchoe, and poinsettia. For specific instructions, refer to “The Ornamental Garden in October,” The Garden Shed, Oct. 2016.
- Remove cool-season weeds, such as chickweed, dandelion, wild onion, plantain, and white clover.
MULCHING LEAVES FOR TURF
If you live in a heavily-wooded area, the prospect of raking and disposing of leaves can be daunting. A thick layer of leaves on a grassy area blocks sunlight and reduces turf growth. The leaves also trap and hold moisture, increasing the potential for turf disease. Numerous university research reports have detailed how leaf mulching affects turf performance. In almost every instance, the results show that chopping up deciduous leaves as part of a regular mowing schedule is an effective means of managing leaves without harming the turf. See the report by Purdue University for more details. Michigan State research touted an overall reduction in dandelions and crabgrass over time because the leaf mulch covered empty areas in the turf where weeds could germinate in the future.
Mulching mowers are the preferred equipment for chopping leaves. To reduce the risk of injury from flying debris, remove sticks and limbs before mulching. Wear safety goggles and an air mask over your mouth and nose to protect yourself from debris and dust. Mulching moist leaves minimizes dust concerns, but if leaves are too wet, the mower’s engine will be stressed and the leaves will not be chopped sufficiently small to easily decompose in the soil. Multiple passes with a mower might be required to thoroughly chop leaves. Set the mower height to 3 inches. Sharpening mower blades and keeping air and fuel filters clean will improve the mulching process and extend the life of the mower engine.
MULCHING LEAVES FOR PERENNIAL BEDS
Fallen leaves can be composted, added directly into the soil, or turned into leaf mold (partially decomposed leaves). See Clemson Cooperative Extension, “Soil Conditioning – Establishing a Successful Gardening Foundation”.
Many homeowners collect carbon-rich leaves and add them to their compost piles, where the leaves help to balance the carbon/nitrogen ratio (kitchen scraps are high in nitrogen) and absorb excess moisture. It is best to shred the leaves coarsely, using a shredder or a lawn mower. Whole leaves have a tendency to blow away, while finely-shredded leaves do not allow water to penetrate.
When used on perennial beds, shredded leaves should be spread 2 inches deep or less; even shredded leaves tend to mat together, restricting the water and air supply to plant roots. As leaf mulch slowly decomposes, it provides organic matter which helps keep the soil loose and provides an ideal environment for earthworms and other beneficial soil organisms. This improves root growth, increases the infiltration of water, and also improves the water-holding capacity of the soil. Organic matter also offers essential plant nutrients such as potassium (K), calcium (Ca), phosphorus (P), magnesium (Mg), and boron (B).
To make leaf mold, leaves should be placed in a pile in the fall, and then turned several times in March and April. Over time, shredded leaves naturally break down into a soft, finely-textured substance called leaf mold. This concentrated material is high in calcium and magnesium and retains three to five times its weight in water. After application, it may only last for 1 to 2 years before completely breaking down and moving into the soil. This process adds significantly to the structure and quality of the soil. Leaf mold can be added to vegetable gardens and landscape beds after the soil has been warmed in the spring. Leaf mold can also be added to potting soil, used to top-dress potted plants, or used as a super-premium mulch.
For a detailed discussion on the benefits of mulching, the use of both organic and inorganic mulches, and how to mulch, refer to the Clemson Extension article, Mulching.
WHEN TO MULCH
Organic mulches (leaf, shredded hardwood mulch, pine bark or other organic mulches) used to help moderate winter temperatures can be applied late in the fall after the ground has frozen but before the coldest temperatures arrive. One of the benefits from winter application of mulch is to reduce the impact of freezing and thawing of the soil in late winter and early spring. The repeated cycle of night-time-freezing and warm-day-thawing can cause many small or shallow-rooted plants to be heaved out of the soil. This displacement exposes their root systems and can cause injury or death. Mulching helps prevent the rapid fluctuations in soil temperature and reduces the chances of heaving.
Soil testing in the fall allows time for corrective pH and nutrient management before new growth starts in the spring. Fall sampling also avoids a sometimes busy spring period at the Soil Testing Laboratory, thus avoiding delays in getting soil test results. Fall can often be a wet season. As a rule, if the soil is too wet to work (or is good for making mud pies), it is too wet to sample. Refer to the VCE publication, “Soil Sampling for the Home Gardener”. As a general rule, soil tests are recommended every three years, unless you note specific problems that indicate testing.
TREE SELECTION AND PLANTING
Late fall is the best time of year to plant or transplant deciduous trees and shrubs. Transplant when the trees and shrubs are dormant but before the ground freezes. Evergreen trees or shrubs may be transplanted earlier in the fall before they go dormant.
For ideas on which trees to plant in our area, see the article by the Virginia Cooperative Extension, “Problem-free Trees for Virginia Landscapes.” Although these suggested trees may not be 100% problem free, they have been tested in our area for disease resistance and hardiness. The list includes both native and non-native trees as well as a list of trees not recommended for planting in our area.
The Ornamental Garden in October, The Garden Shed, 10/17, http://piedmontmastergardeners.org/article/the-ornamental-garden-in-october-3/
- Look for topics such as: October-blooming perennials; why leaves change color; regulating light for photoperiodic plants such as Christmas cactus and poinsettia,
“The Ornamental Garden in October,” The Garden Shed, 10/16, http://piedmontmastergardeners.org/issue/october-2016/
- Look for topics such as: October-blooming perennials; fall maintenance; caring for houseplants.
“The Ornamental Garden in October,” The Garden Shed, 10/15, http://piedmontmastergardeners.org/article/the-ornamental-garden-in-october/
- Look for topics such as: which perennials to cut back and which to leave standing, planting cool-season annuals.
“October Tips: Perennials, Annuals and Bulbs,” Virginia Cooperative Extension, https://albemarle.ext.vt.edu/content/dam/albemarle_ext_vt_edu/files/hort-tip-sheets/10-14-perennials.pdf
“October Tips: Trees, Shrubs and Groundcovers,” Virginia Cooperative Extension, https://albemarle.ext.vt.edu/content/dam/albemarle_ext_vt_edu/files/hort-tip-sheets/10-14-trees-shrubs.pdf
“Making Compost from Yard Waste” http://pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/426/426-703/426-703_pdf.pdf
“Spring-Flowering Bulbs,” http://piedmontmastergardeners.org/article/spring-flowering-bulbs/
“Making Compost from Yard Waste,” Virginia Cooperative Extension, https://pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/426/426-703/426-703_pdf.pdf
“Leave Them Alone—Lawn Leaf Management,” Virginia Cooperative Extension, http://pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/430/430-521/430-521_pdf.pdf
“Backyard Conservation: Mulching,” https://www.nrcs.usda.gov/wps/portal/nrcs/detail/?cid=nrcs143_023585
“Soil Testing for the Home Gardener,” Virginia Cooperative Extension, http://pubs.ext.vt.edu/452/452-129/452-129.html
“Mulch,” Clemson Cooperative Extension, https://hgic.clemson.edu/factsheet/mulch/
“Soil Conditioning—Establishing a Successful Gardening Foundation,” https://hgic.clemson.edu/factsheet/soil-conditioning-establishing-a-successful-gardening-foundation/
“Problem-free Trees for Virginia Landscapes,” Virginia Cooperative Extension, https://pubs.ext.vt.edu/450/450-237/450-237.html