Episode 1: Mid to Late September
Welcome to the very first episode of The ATXGardens Podcast with landscape consultant and certified arborist Colleen Dieter of ATXGardens.com!
In this episode, Colleen walks you through exactly what to do in your Austin and Central Texas garden during late September—a transitional time between summer heat and fall planting.
If you’ve been wondering when to fertilize, what to prune (or not prune), which plants to divide, or how to prep your vegetable beds for fall crops, this episode covers everything you need.
🌼 Late-September Garden Big-Picture Tips
As we shift into fall, the goal is to slow plants down, not speed them up.
🚫 Skip pruning
Do not trim trees, shrubs, or perennials right now. Pruning triggers tender new growth at exactly the wrong time—just as plants need to wind down for winter.
🚫 Last call for fertilizer
Mid-September is your final chance to fertilize lawns, roses, trees, and perennials. After October 1, fertilizer forces growth that can be damaged by winter cold.
✔️ Do a soil test instead
If you’re unsure what your soil needs, fall is the perfect time to send a sample to:
Texas A&M Soil Lab
Texas Plant & Soil Lab
Any reputable U.S. soil testing service
This is especially important for vegetable beds and fruit trees, which are heavy nutrient users.
🍄 Manage fungal diseases early
Warm, damp September weather encourages fungal issues.
Use:
Cornmeal on fungal spots in turf
Actinovate (linked at ATXGardens.com) to inoculate soil and turf
Homemade compost tea to boost beneficial microbes
🌳 Trees, Shrubs & Woody Plants
Mid-September marks the start of woody plant season—trees, shrubs, woody vines, and roses.
🌳 The best time to plant trees
Planting season runs from mid-September through mid-March, with dormancy being the ideal time for roots to establish.
Trees may start dropping leaves soon—don’t let that scare you off. Discounted trees are often perfectly healthy, just temporarily unattractive.
🍂 Prepare your leaf-management tools
If you use a leaf blower, this is the time to:
Check batteries or cords
Get gas-powered models serviced
Consider switching to electric (quieter + more sustainable!)
Colleen will talk more about leaf strategy in upcoming episodes.
🕸️ Webworms in pecans & shade trees
September is peak season for webworm tents:
A couple of webs? Totally fine.
More than 1/3 of the tree? Take action.
What to do:
Pull down reachable webs and dispose of caterpillars
Prune out infested branches if safe to reach
At minimum, poke holes to allow predatory wasps to access the caterpillars
🌳 Seed to Tree Partnership
Colleen is the founder of Central Texas Seed Savers, and fall is the perfect time to gather:
Acorns
Pecans
Native tree seeds
Send them to TreeFolks, where they are grown into seedlings for local reforestation. Link in show notes.
🌹 Roses
Spray roses with:
Compost tea, or
Arbor Biofungicide (linked in show notes)
to prevent black spot and other fungal issues.
🌸 Perennials & Bulbs
Now is an excellent time to plant or divide perennials and bulbs.
🌼 Plant now:
Salvias
Indigo spires
Most ornamental grasses
Southern-adapted bulbs (rain lilies, crinums, oxblood lilies, etc.)
✂️ Divide now:
Irises
Daylilies
Canna lilies
Amaryllis (Hippeastrums)
And any large, floppy perennials
Colleen’s booklet series “Let’s Care for Texas Plants” (available at ATXGardens.com) includes diagrams and instructions for dividing all of these successfully.
🐦 Nature Stuff
What’s happening in Central Texas nature right now?
✨ Hummingbirds!
Fall migration begins in late September.
Clean and refill feeders
Add plants hummingbirds love:
Wax mallows
Common sunflowers
Pokeweed (a favorite at Colleen’s home garden)
Plants provide better nutrition than feeders, so think about adding some hummingbird-friendly species this fall.
🥬 Vegetables
Late September is the big transition from summer crops to cool-season planting.
🌱 Remove warm-season crops that are winding down:
Okra
Black-eyed peas
Melons
Peppers
Tomatoes
You can keep healthy plants until the first freeze, but it’s also fine to clear beds now. Save one plant of each type if you’re interested in seed saving.
🥕 Plant cool-season vegetables now:
Direct-sow:
Arugula
Radishes
Mustard
Turnips
Bok choy
Swiss chard
Beets
Collards
Kale
Peas
Transplant:
Broccoli
Cauliflower
Cabbage
Plant as transplants:
Artichokes
Cardoons
🌾 If you’re taking a winter break
Plant a cover crop such as:
Alfalfa
Rye
Clovers
Winter peas
Texas bluebonnets
Cover crops feed microbial life and protect soil during your rest season.
🌿 Herbs
Late September is the time to:
✔️ Plant perennial herbs:
Oregano
Sage
Thyme
Chives
Rosemary
✔️ Clear out warm-season annuals:
Basil (perfect moment for pesto!)
✔️ Prepare for planting cool-season annual herbs (in early October):
Cilantro
Parsley
Dill
Fennel
Calendula
Always add compost before planting new herbs.
🌼 Wildflowers
Late September is prime time for wildflower seeds—especially:
Bluebonnets
Poppies
Larkspur
🌸 Colleen’s wildflower planting recipe:
Mix in a wheelbarrow:
-1 bag compost
-1 bag granite sand
-Your wildflower seed packet(s)
Rake soil to roughen the surface
Spread seed mix
Walk over it to ensure soil contact
Perform your funkiest rain dance
This is a perfect kid-friendly or friend-friendly fall project.
🔗 Links & Resources Mentioned
Make an appointment or shop at: ATXGardens.com
Connect on Instagram: @atxgardens__
‘“Let’s Care for Texas Plants” maintenance guide
Arber Bio-Fungicide (commissions earned): https://amzn.to/47K5XdV
Collect Tree Seeds with Seed to Tree Partnership: https://www.centexseedsavers.org/seed-to-tree-partnership
Actinovate Bio-Fungicide (commissions earned): https://amzn.to/4mwznAV
Texas Plant and Soil Lab soil testing: https://www.tpslab.com/
Digging fork (commissions earned): https://amzn.to/45RnQFe
Border spade (commissions earned): https://amzn.to/4n0T3g9
🌼 Stay Connected
For more Central Texas garden tips, visit ATXGardens.com, follow Colleen on Instagram @ATXGardens_, and don’t forget to subscribe to The ATXGardens Podcast for biweekly updates straight from your favorite Austin garden consultant.
