By Terry Deem-Reilly, CSU Extension – Denver Master Gardener since 2003
Anything can happen in a Colorado November: our first hard freeze (or the second or the third), or nighttime temperatures stuck at 45F. Lawns and gardens can suffer from heavy wet snow (with the splintered tree limbs littering the streets to prove it) or prolonged dryness that has gardeners alternating watering with leaf raking. Despite the unpredictability of autumn, winter will eventually arrive (probably with two feet of snow on Thanksgiving Eve), so our focus this month is on closing out the 2022 season and preparing for Spring 2023.
- Harvest any remaining vegetables; we can have a killing frost and/or snow that will wither produce anytime now. Farm Calculators offers an extensive list of veggies for autumn harvest; if mild weather has gifted us with green tomatoes, try ripening some to use on Thanksgiving! Minnesota Extension has compiled some great hints on harvesting AND storing late-season produce.
- Finish cleanup now while temperatures remain mild. Pests and diseases will overwinter in plant debris and afflict the garden next spring and summer – and no one feels like working outside in a December snow squall!
- Spread compost over the soil and turn it in – it feeds the microscopic critters that will deliver nutrients to your plants’ roots next year.
TREES AND SHRUBS
- Pruning trees and shrubs can wait a few months, according to the schedules outlined in the Plant Talk articles Pruning Shrubs and Pruning Shade Trees. Dead tree branches, however, should be removed ASAP so they don’t become a hazard in heavy snow accumulations. (Many arborists offer discounts for off-season services.) Ditto for all dead bits on shrubs and roses.
- Keep watering weekly until the ground freezes – usually around Thanksgiving at Denver’s elevation.
- Check mulch levels to ensure that soil moisture remains adequate to maintain healthy roots. Mulch should cover the root balls without crowding the stems or trunks.
- Irrigation during winter warm periods is also key to helping roots support plant growth next year. Consult the Extension Fact Sheet “Fall and Winter Watering” for details on winter watering.
- Wrap the trunks of trees too young to have formed bark to prevent sunscalding during periods of alternate warming and freezing in the winter. During warm periods, tree trunks take up water into their cells, which then burst when temperatures drop below freezing, killing bark and conductive tissue. “On at Thanksgiving, off on tax day” is a good rule of thumb for utilizing tree wrap.
- Consider using protection like plant bags and burlap around evergreens prone to drying out in winter winds.
- Put rose collars around your roses and fill the collars with leaves for insulation, or mound soil over the bud union of each plant.
- Make sure that nonxeric and new xeric/native perennial plants are mulched to a depth of at least one-and-a-half to two inches. Pull the mulch back from the crowns to forestall crown rot and discourage pests from burrowing around the plant.
- Keep watering perennials until the ground freezes and throughout the winter as prescribed by the fact sheet referenced above.
- Postponing deadheading and cutting perennials back until spring offers several advantages to your garden: many perennials produce seedheads and stems that offer cold-weather food and shelter to birds, beneficial insects, and other wildlife; intact stems also protect crowns from freezing and catch snow to deliver more moisture to the plants.
- It’s a bit outside the recommended planting time, but If you still have bulbs to plant and the soil is workable, do it now. Since roots will have less time to develop, flowering may be reduced, but you still may enjoy spring blossoms. Make sure to water them in well.
- Rake up leaves so they don’t mat on the turf and promote mold growth. Running a mower over piles of leaves will produce free mulch to spread over plant beds (and free nutrients as the leaves decompose)!
- Blow out and shut off sprinkler systems if you haven’t done so already. If time and weather permit and the turf looks dry, irrigate one more time.
- Clean, sharpen, and oil tools; get that lawnmower blade sharpened while you’re not distracted by spring gardening tasks.
- Consider what plants to add next year – gardening catalogs will start arriving next month! And continue to contact Denver County Extension with all your gardening questions.
ONE MORE THING
It’s been my pleasure to contribute to this blog this season, but my short posts can cover only a few essentials. Therefore, here’s a fall task list that not only adds another dimension to your fall garden experience but also allows me to make a small homage to a most distinguished horticulturist whom we lost this year: Ten Key Tips for the Fall Garden.