The Boise Fall Garden Checklist: 10 Things to Do This September
September 10, 2026 | News
September in Boise is one of those months when your garden can feel a little confused. Summer isn’t quite over, but cooler mornings are here, the days are getting shorter, and suddenly fall is just around the corner.
The good news? Your gardening season isn’t over. In fact, September is one of the best times to get outside and make a few important updates to your Boise garden.
From planting cool-season vegetables to refreshing your porch containers, there is still plenty to do. And a little work now can mean a healthier, more beautiful garden next spring.
Here is your September garden checklist for Boise, Idaho.
1. Plant Trees, Shrubs & Perennials
If you’ve been thinking about adding a tree, shrub, or perennial to your landscape, fall is a great time to do it.
The cooler temperatures make planting much less stressful for new plants, while the soil can remain warm enough for roots to continue developing. That gives plants a chance to establish their root systems before winter arrives.
Fall planting can also mean less heat stress and less transplant shock compared with planting during the heat of a Boise summer.
Thinking about adding something new to your landscape? September is a great time to start planning.
Just remember that newly planted trees and shrubs still need consistent watering while they establish, even as temperatures begin to cool.
2. Plant Your Fall Vegetable Garden
Don’t put away your gardening gloves just yet. Your vegetable garden can have a whole second season.
Cooler weather is perfect for many fall vegetables, including:
- Kale
- Lettuce
- Swiss chard
- Beets
- Cabbage
- Brussels sprouts
- Scallions
- Leeks
Fall-grown vegetables can actually thrive in cooler temperatures, and some can tolerate light frosts.
If your summer vegetable garden is winding down, pull out tired plants and replace them with cool-season crops. You may be surprised by how much you can still grow in Boise.
3. Refresh Your Porch Containers for Fall
This is one of our favorite September gardening projects and one of the easiest ways to instantly make your home feel ready for fall.
You don’t necessarily need new pots. Start with the containers you already have and give them a seasonal refresh.
Swap out tired summer annuals for fall favorites like:
- Mums
- Ornamental peppers
- Ornamental kale
- Violas
- Celosia
- Ornamental grasses
- Cool-season foliage plants
For an extra fall touch, tuck a small pumpkin or gourd into your container. You can also add interesting branches, twigs, or dried stems from your own garden for texture.
The result? A porch that feels completely different without having to start from scratch.
4. Start Thinking About Spring Bulbs
Spring may seem a long way away, but fall is when you need to think ahead.
Spring-flowering bulbs such as tulips, daffodils, crocus, and alliums are planted in the fall so they can establish roots before winter.
If you want a colorful spring garden, don’t wait until spring to think about it.
Choose a sunny, well-draining location and plan your combinations now. Planting bulbs in groups or drifts can create a much bigger visual impact than planting them individually.
5. Give Your Garden One Last Good Weeding
Not the most exciting item on the list, but September is a great time to get ahead of weeds before winter.
Pull weeds while they’re still manageable and try to remove as much of the root system as possible. Allowing weeds to go to seed can create an even bigger problem next spring. A little time spent weeding now can save you plenty of time later.
6. Start Adjusting Your Watering
Just because the temperatures are cooling down doesn’t mean you should suddenly stop watering.
Newly planted trees, shrubs, perennials, and fall plantings still need consistent moisture while their roots establish.
However, your landscape’s water needs will gradually change as temperatures drop and days get shorter.
Keep an eye on your soil and your plants rather than watering simply because it’s the day your irrigation system is scheduled to run.
The goal is healthy, hydrated roots, not constantly wet soil.
As fall progresses, continue adjusting your irrigation schedule based on weather conditions and your landscape’s needs.
7. Add Mulch to Your Garden Beds
Fall is a great time to check your mulch.
A layer of organic mulch can help regulate soil temperature, retain moisture, and protect plant roots as temperatures fluctuate.
If your garden beds look a little bare, add a fresh layer around trees, shrubs, and perennials.
Just remember: keep mulch away from the trunk of trees and the crowns of plants. Mulch should look more like a donut around a tree than a volcano.
8. Don’t Cut Everything Back Yet
It can be tempting to look at your garden in September and think, “Time to clean everything up.”
Not so fast.
Some plants provide valuable winter interest, while seed heads can provide food for birds and habitat for beneficial insects.
Instead of cutting everything back at once, take a more selective approach.
Remove diseased or damaged plant material, but consider leaving healthy stems, ornamental grasses, and interesting seed heads through the winter.
Your garden doesn’t have to look perfectly manicured every day of the year.
9. Check Your Trees and Shrubs
September is a great time to walk around your landscape and actually look at your plants.
Check for:
- Dead or damaged branches
- Signs of disease
- Pest problems
- Overgrown areas
- Plants that may have outgrown their location
- Trees or shrubs that need additional support
This is also a great time to start thinking about larger landscape projects you’d like to tackle once the weather changes.
Maybe that empty corner needs a new tree. Maybe your foundation beds need an update. Or maybe you’re finally ready to create the garden you’ve been talking about for years.
Fall is a great time to start making that plan.
10. Make a Garden Plan for Next Spring
One of the best things you can do in your Boise garden this September doesn’t involve planting anything at all.
Pay attention.
What worked this summer? What didn’t? Which plants thrived in your yard? Which ones struggled in the heat? Is there a spot that needs more shade? Do you need more color? More privacy? More pollinator-friendly plants?
Take a few photos of your garden now. Make notes about what you love and what you’d change. By the time spring arrives, you’ll already have a plan.
Your Boise Garden Isn’t Done Yet
September is a transition month, but that doesn’t mean your garden is winding down. Fall is actually one of the most productive times of year for Boise gardeners.
Plant vegetables. Refresh your containers. Add a tree or perennial. Plant spring bulbs. Mulch your beds. And take some time to enjoy the garden before the seasons change.
If you’re not sure what to plant or what your garden needs this time of year, stop by FarWest Garden Center. Our team can help you choose plants that are suited to Boise’s growing conditions and help you make the most of your fall garden.
Happy fall gardening, Boise!