Colorado Master Gardeners - Arapahoe County

10/22/2026

Fall is the ideal time to control PERENNIAL weeds such as bindweed and black medic. Weeds are actively storing food in their root systems for the winter, and readily absorb herbicides applied at this time, thus weakening or killing the plant. ANNUAL weeds such as redstem filaree and purslane die back with a few frosts, but they can be dug out or sprayed with a burndown product. IMPORTANT: read and follow all herbicide labels.
https://www.k-state.edu/news/wild-west-district/articles/2021/10/fall-is-the-best-time-to-control-dandelions-and-perennial-weeds.html
https://yardandgarden.extension.iastate.edu/how-to/how-manage-perennial-broadleaf-weeds-garden-and-lawn

10/19/2026

Late-season visitors have been busy lately, gathering food/resources for the winter. Honeybees and moths are actively feeding on Salvia ‘Mystic Spires’ and Salvia ‘Black & Blue,’ and hummingbirds are visiting each day as they migrate south. Leaving up feeders and plants that are still blooming can help pollinators and birds transition to winter.

10/15/2026

Frost heave occurs when repeated freezing and thawing pushes shallow-rooted perennials out of the ground, exposing roots and crowns to cold temperatures and drying winds. Prevent frost heave by applying 3–4 inches of mulch after the ground freezes. Mulch insulates the soil, moderates temperature fluctuations, and reduces freeze-thaw cycles that push plants upward.

10/14/2026

Spooky Plant Pathogens: Creepy Cases from the Garden
Wednesday, October 14, 2026, 12:00pm MT
Join Drs. Jen Rushton and Emily Luna, from CSU, for a Halloween-themed dive into the world of plant diseases. Explore fungi that resemble monsters, bacteria that ooze like slime, and other chilling plant pathology phenomena. Perfect for anyone who loves plants—and a good scare! Register here:https://zoom.us/webinar/register/WN_jj8qfm8FQXyWpyKrar_SAQ #/registration

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10/13/2026

Spooky Plant Pathogens: Creepy Cases from the Garden
Wednesday, October 14, 2026, 12:00pm MT
Join Drs. Jen Rushton and Emily Luna, from CSU, for a Halloween-themed dive into the world of plant diseases. Explore fungi that resemble monsters, bacteria that ooze like slime, and other chilling plant pathology phenomena. Perfect for anyone who loves plants—and a good scare! Register here:

Join Drs. Jen Rushton and Emily Luna, from CSU, for a Halloween-themed dive into the world of plant diseases. We’ll explore fungi that resemble monsters,

10/12/2026

The mums are out, and autumn is here! The National Chrysanthemum Society divides mums into two groups: GARDEN HARDY, perennials with a looser growth habit, leafier foliage, and smaller blooms, and EXHIBITION, typically grown as annuals for fall décor and gifts. They have a tighter, more rounded growth habit and are bred in countless colors for maximum flower power. Within these two groups are 13 official classes based on bloom forms and petal shapes. Which is your favorite?

10/08/2026

In Ancient Greek, “Parthenos” means virgin and “Genesis” means creation. Oleander aphids (Aphis nerii), also called yellow milkweed aphids, are PARTHENOGENETIC: all are female and able to reproduce without mating, so populations grow rapidly. Control methods include insecticides, insecticidal soap, or a strong jet of water. Natural enemies also help control aphids. Warning: Insecticides will harm beneficial insects and larvae.
More on aphids:
https://extension.colostate.edu/resource/aphids-on-shade-trees-and-ornamentals/

Photo: Aphids on Dipladenia, Donnetta Wilhelm

10/07/2026

As days get shorter, trees get less sunlight. With less sunlight, trees make less chlorophyll, so the green color fades. Yellow and gold colors come from pigments called carotenoids that are already in the leaves. Orange and red colors come from anthocyanins, which trees start making in the fall. Read more here:
https://planttalk.colostate.edu/topics/trees-shrubs-vines/1728-leaves-change-color-fall/
photo: Donnetta Wilhelm

09/30/2026

Fall landscaping clean up: Leaf it alone

Instead of collecting and hauling leaves from your property this fall, consider ways you can put them to use. Lisa Mason, a CSU Extension horticulture and entomology specialist in Arapahoe County, said leaf debris is an effective mulch to use under trees, shrubs, and in perennial beds. - Read more - https://source.colostate.edu/8-ways-to-prep-your-lawn-garden-and-trees-for-fall-and-winter/

Read about fall lawn care. - https://planttalk.colostate.edu/topics/lawns/1523-fall-lawn-fertilization/

https://yardandgarden.extension.iastate.edu/how-to/fall-garden-tasks