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Jun 14, 2023

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If you want a colorful spring, remember to plant your bulbs in fall! Gardeners sometimes worry, but it is normal for all pine trees to drop their older interior needles in fall. LOOK: To read more

If you want a colorful spring, remember to plant your bulbs in fall!

Gardeners sometimes worry, but it is normal for all pine trees to drop their older interior needles in fall.

LOOK: To read more Gardening Etcetera columns, point your smartphone camera at the QR code, then tap the link.

As the mornings have a slight chill in the air, the first signs of fall can be seen in the garden. Plants like ‘Autumn Joy’ sedum and aster come into bloom, while midsummer bloomers including coreopsis, coneflower and black-eyed Susan finish flowering. Berries on shrubs and trees ripen in earthly tones of red and orange as the interior needles of pine trees yellow, shedding their old growth. In the vegetable garden, squash, beans, potatoes and other crops are in full harvest. And of course, the first leaves start to change color lighting up our gardens in hues of red, yellow, and orange. It truly is a magical time!

As the heat and rapid growth of summer wane, there is a stillness and sense of completion in the September garden. However, there is still lots to do and enjoy as we cherish these fleeting days on our slow march to winter. Here is a checklist of fall jobs to focus on in the coming weeks.

Seasonal color

-- As plants freeze or to make room for fall annuals, remove summer seasonal color in beds. Add plants to the compost pile and mulch beds as needed.

-- Empty, scrub, and store hanging flower baskets for next year.

-- In containers and beds, plant fall annuals such as asters, mums, pansies/violas, and ornamental kale. You can also plant cold hardy evergreen perennials such as juniper, euonymus, heather, kinnikinnik, and centerpieces like red stem dogwoods or hollies that can remain in pots throughout the winter.

-- By early October, finish planting hardy trees, perennials, and shrubs. The fall is a great time to plant, as the warm days and cool nights are ideal for root growth and establishment.

-- As nighttime temperatures drop below freezing, bring cold-sensitive plants like geraniums, fuchsia and begonias into the greenhouse or indoors with sufficient light, space, and warmth.

-- Toward the middle of October to early November, plant spring-blooming bulbs such as daffodils, crocus, hyacinths, tulips and allium.

Bed maintenance

-- To slow growth and prepare plants for winter, stop fertilizing annuals, perennials, roses, trees, and shrubs.

-- Don’t prune the flower heads on ornamental grasses. Leave these for winter interest until heavy snow topples them over.

-- Properly identify and remove invasive weeds before they set seed such as Scotch thistle (Onopordum acanthium), Canada thistle (Cirsium arvense), knapweed (Centaurea spp.), mullein (Verbascum thapsus) and toadflax (Linaria spp.). Remember the old saying: “One-year seeding is 7 years of weeding.” Also, watch for and remove cool-season weeds as they germinate.

-- Trim back shrubs as needed but wait for renewal shrub-pruning until plants are dormant late winter.

-- Continue to deadhead (removing the spent flowers) perennials as they go out of flower but leave seed heads on plants that provide food for wildlife such as black-eyed Susan and coneflower. As herbaceous perennials (such as daylilies, hostas, and salvia) yellow and go dormant cut plants back to just above the growing crown. Remember not to cut evergreen or semi-evergreen perennials such as basket-of-gold, candy tuft, dianthus, creeping phlox, and lavender. These will remain green for the winter.

-- Leaves! Leaves! Leaves! As leaves begin to fall, gather and spread them as mulch or add to the compost pile. Mow up leaves from lawns so not to smother the grass.

Irrigation

-- To prepare for winter, decrease watering frequencies to established trees and shrubs. Deeply water roses, perennials, and new plants to help prepare root systems for winter.

-- Keep watering lawns as needed until hard freezes set in.

-- By mid-November, winterize your irrigation by contacting a licensed professional landscaper to use compressed air to blow out your system. By removing residual moisture in your valve heads and pipes, this helps prevent damage that can occur as the water freezes, thaws and expands during extended periods of hard freezes.

-- Hope for winter snow to insulate your plants and water them so they don’t succumb to winter dehydration.

In celebration of the ideal planting conditions of fall, The Arboretum at Flagstaff will be hosting our annual Fall Plant Sale on September 9 (9-11 a.m. members only; 11 a.m.-3 p.m. open to the public). Members receive 10% off plants, while admission is free all day to the public.

SKYWARN is a program that trains volunteers to help keep their local communities safe by providing timely and accurate reports of monsoon season weather to the National Weather Service. (Video courtesy of Flagstaff NWS)

Nate O’Meara is the Executive Director of the Arboretum at Flagstaff (www.thearb.org) and has worked as an ethnobotanist and horticulturist. This article was adapted from his blog www.omearagardens.com.

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