September Garden Checklist for the Southwest

Summer's winding down and temperatures are cooling—time for desert gardeners to venture out and refresh landscapes with new trees, shrubs, and succulents. Upper-elevation gardens offer harvest-ready fruits and vegetables, and it's prime time to plant bulbs for a spring show.

Low Deserts (up to 3,000 Feet)

Add Texture with Uniquely Shaped Succulents

Spiky agaves contrast beautifully with rounded shrubs, adding distinctive design flair. Plant large agaves like octopus agave (Agave vilmoriniana), smooth leaf agave (Agave desmettiana), or Weber's agave (Agave weberi). Surround each with three to five flowering ground covers: purple trailing lantana (Lantana montevidensis), verbena (Glandularia spp.), blackfoot daisy (Melampodium leucanthum), or prostrate rosemary (Rosmarinus officinalis 'Prostratus').

Shown: Weber's agave with gopher plant (Euphorbia biglandulosa)

Fertilize Palm Trees

Palms uptake fertilizer only in warm soil, so feed during summer months. Use a palm-specific fertilizer with major nutrients and micronutrients. Follow package directions carefully, water deeply after applying. When in doubt, apply less—excess burns plants.

Shown: Mediterranean fan palm (Chamaerops humilis)

Prepare Vegetable Garden for Cool-Season Edibles

Add a 3-inch layer of compost or manure to existing soil and lightly rake in. Toward late September, plant broccoli and cauliflower from seed or transplants.

Shown: Broccoli

Give Citrus Trees Their Final Fertilizer Application

Citrus needs feeding three times yearly: late winter, early summer, late summer. Apply citrus fertilizer around the base to the drip line (where most roots are). Water before and after for best root uptake.

Shown: Kumquats

Mid- to High Deserts (3,000 to 6,000 Feet)

Spice Up a Boring Garden with Ornamental Grasses

These grasses earn their name—softly mounded shapes beautify the landscape. Fall brings plumes in burgundy to tan, depending on species. Plant in groups of three or five: gulf muhly (Muhlenbergia capillaris 'Regal Mist'), deer grass (Muhlenbergia rigens), or Mexican feather grass (Stipa tenuissima).

Shown: Regal Mist pink muhly (Muhlenbergia capillaris 'Regal Mist')

Rejuvenate Old Perennials by Dividing

If older perennials aren't flowering like they used to, divide them (separate root systems into multiple sections for replanting). Daylily, Shasta daisies, coneflower, and iris benefit from division every three years. Use a shovel to separate and replant or share with friends.

Shown: Shasta daisy (Leucanthemum x superbum)

Swap Warm-Season Annuals for Cool-Season Flowers

As fall approaches, switch from summer annuals to winter-thriving flowers. Amend soil with compost and slow-release fertilizer before planting. Create container combos with three different plants: yellow snapdragons centered, deep purple petunias, white alyssum edging; or bright pink geraniums with white petunias and blue lobelias.

Shown: Snapdragons

Fertilize Warm-Season Lawn

Even though summer lawns will soon go dormant, fall fertilizing strengthens roots for earlier spring green-up.

Plant Leaf Lettuce

Easy from seed or transplants. Fresh homegrown lettuce far surpasses store-bought.

Shown: Leaf lettuce

Upper Elevations (Over 6,000 Feet)

Harvest Tomatoes Before First Frost

September usually brings first frost—pick all tomatoes, green ones included. They'll ripen indoors.

Plant Spring-Blooming Bulbs Now

Spring bulbs are the harbingers of spring—plant now so roots establish before ground freezes. For maximum impact, plant crocus, daffodil, hyacinth, or tulip bulbs in large swaths, not single rows.

Shown: Blue hyacinth

Grow Your Own Garlic

Plant now for a flavorful summer harvest. Easy: plant individual cloves 2 inches deep, pointed end up, 6 inches apart in rows 1 foot apart.

Preserve Summer Herbs by Drying

Tie herbs in bunches, hang in a dry, dark area for a few weeks. Crumble dried leaves, store in sealed jars, use to flavor dishes.

Get ready for October: Plants need less water as temperatures cool—adjust irrigation controllers accordingly.