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August/September 2021 Garden Checklist

What to Plant: Low Elevations


Sow seeds of bush beans, muskmelons, cucumbers, squash and pumpkins. Select varieties that will be ready for harvest before the first predicted frost, which is, on average, Nov. 24 in Tucson, Dec. 11 in Phoenix and Dec. 18 in Yuma.


Start seeds of Brussels sprouts, head cabbage, cauliflower and broccoli indoors to transplant outside in October and November. Directly sow radish, turnips, beets, parsnips, carrots and rutabaga outdoors, once daytime temperatures consistently fall below 105 degrees, to ensure maximum germination.


Install tried-and-true types, such as pygmy date palm (Phoenix roebelenii), which reaches about 8 feet tall and wide; Mediterranean fan palm (Chamaerops humilis), which will grow 15-20 feet tall and wide; or pindo palm (Butia capitata), which matures to about 20 feet in height and 10 feet wide. Dig the planting hole no deeper than the root ball but at least twice the width. This will allow roots to more easily colonize the surrounding soil. Be careful not to plant too deeply or pack soil around the trunk, as this will make it prone to bacteria that can harm the plant.


Succulents, which include cacti, come in a seemingly endless variety of sizes, shapes and colors. Some types, such as ponytail palm (Beaucarnea recurvata), snake plant (Sansevieria trifasciata) and aloes do well as houseplants or planted in a shady, protected location outdoors.

Mimosa (Albizia julibrissin)

What to Plant: Middle and High Elevations


Transplant or direct seed beets, radish, kale, chard, spinach, leaf lettuce and arugula into soil that has been enriched with compost. Prior to planting, rake soil smooth for an even bed, which will support more uniform germination. Keep soil moist, but not waterlogged, until emerged seedlings have two to three true leaves. To protect against whiteflies and birds, cover new plantings with floating row covers, available at most garden shops.


Transplant pansies, violas and mums into containers or directly into garden beds. Plant spring-blooming bulbs with the round end down and pointed end up into holes about 2 inches deeper than the length of the bulb. Cover bulb beds with mulch or straw to suppress weed germination. Place taller types in the background so you can easily see shorter specimens in the foreground.


Late summer is a good time to install permanent landscape plants because the warm days and cool nights are optimal for root growth. For a riot of blooms next summer, plant crepe myrtle (Lagerstroemia spp.) or mimosa (Albizia julibrissin). To attract butterflies, try English lavender (Lavandula angustifolia), French lavender (L. dentata), black-eyed Susan (Rudbeckia hirta), purple coneflower (Echinacea purpurea), and Western redbud (Cercis occidentalis). Native species, such as manzanita (Arctostaphylos spp.), mountain mahogany (Cercocarpus spp.) and alligator juniper (Juniperus deppeana) will require virtually no maintenance once established, approximately three years after planting.

Garden Maintenance: All Elevations


As summer winds down and the days grow shorter, temperatures start to fall and humidity rises, resulting in lower overall plant water needs. Extend the time interval between irrigating landscape plants and turf by one day each week beginning in September. Apply the same amount of water when you do irrigate to ensure you wet as many of the roots as you can.


Monsoon rains may bring a flush of weeds. Use a hula hoe, which has a smaller head and easier cutting action for garden areas, to uproot weed seedlings. Check the undersides of leaves for masses of eggs laid by plant-eating insects. Simply pluck the affected leaf from the plant and dispose in the trash. Kill aphids by spraying with insecticidal soap (available at many garden centers) in the late afternoon, after most bees have returned to their homes for the day. Use a strong stream of water to wash the foliage of cypress, juniper and arborvitae and remove spider mites.


Remove any limbs that were broken during summer storms. Use a pruning saw to cut limbs greater in diameter than 1 inch. To clean up heavy limbs, three cuts may be necessary to avoid stripping the bark. The final cut should begin beneath the branch bark ridge and end just outside of the branch collar. If the cut is made flush against the trunk, the tree may be unable to seal off the damage and will be prone to invasion by wood-destroying pests.


Check if staked trees are able to stand without support. If so, remove the stakes and ties. Leaving the stakes in place after they have served their purpose can damage the trunk and branches. If the tree still flops over without support, adjust the ties so they are at the lowest point on the trunk that holds it up. Keep the ties somewhat loose to allow the trunk to sway in the wind and become stronger.


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