As the intense heat of summer begins to wane, September in Tucson presents a prime opportunity for gardeners to refresh their plots and beds and prepare for the cooler months ahead. Our desert climate, characterized by its arid conditions and dramatic temperature fluctuations, requires specific strategies to keep your garden thriving. Here’s what we can be doing in September to set up our gardens for success here in Tucson:
Prune
With the daytime highs hopefully beginning to duck under 100, the opportunity to clean up sun-sensitive plants presents itself:
- Aesthetic Pruning: Around the middle of the month, prune out any dead, rangy, or burned growth on herbaceous perennials and annuals. Take special care when pruning woody perennials, as many bloom on old wood.
- Prune Roses: In mid-month, prune rose canes back by 1/3. This will encourage a lush fall flush of blooms.
- Prune Overgrown Vegetables: Peppers, eggplant, and tomatoes can be cut back to the newest set of leaves to encourage a fall crop.
- Remove Shade Cloth: Towards the middle to end of this month, you may begin to remove any summer shade cloth you may have been using to protect sun-sensitive plants. The sunlight will become less intense as we get further into the month.
Plan and Prep
September is an excellent time to evaluate and enrich your soil. The summer monsoons may have brought some moisture, which can help loosen compacted soil. Consider the following:
- Test Soil pH: Use a soil test kit to check the pH and nutrient levels. Apply soil sulfur to acid-loving plants and any planting areas with non-native plants. A pH of 7 is neutral and preferred by most non-natives.
- Adding Organic Matter: Amend the soil as necessary with compost or well-rotted manure to improve fertility and water retention. This also feeds the soil microorganisms and helps create a loamy soil structure.
Plant
With the cooler temperatures coming, many plants will thrive if planted now. Here’s what you can focus on:
- Cool-Season Vegetables: September is ideal for sowing seeds or transplanting cool-season crops such as lettuce, spinach, peas, broccoli, radishes, and carrots. These crops will grow well in the milder temperatures of fall. If temperatures are still in the 100s, sow indoors and wait to plant cool-season vegetables until later in the month.
- Herbs: Plant herbs like cilantro, parsley, and dill. They prefer the cooler fall temperatures and will have time to establish before winter.
- Perennials and Shrubs: This is an excellent time to plant perennials and shrubs, allowing them to establish roots before the winter. For optimal water efficiency, opt for native plants adapted to Tucson’s climate.
- Potatoes: Begin chitting seed potatoes to be ready for planting late in the month.
Water
Watering needs to change as temperatures begin to drop, but Tucson’s arid climate still requires careful attention:
- Adjust Watering Schedule: As the weather cools, reduce the frequency of watering for established plants. However, ensure new plantings continue to receive adequate moisture to establish strong root systems. Generally, mid-late September is an ideal time for installing and establishing new plants without the burden of an intensive daily watering regime.
- Mulching: Apply a layer of mulch 3-4″ deep around plants to help retain soil moisture and regulate soil temperature. This also reduces the risk of weeds and erosion. Adding 5-6″ of mulch to the base of cold-sensitive semi-tropical plants can help them survive any hard winter freezes.
Pest and Disease Management
While pest activity may decrease in September, vigilance is still necessary:
- Monitor for Pests: Keep an eye out for pests such as aphids, spider mites, caterpillars, and whiteflies. Use organic pest control methods when necessary, such as neem oil, B.T., or insecticidal soap.
- Disease Control: Ensure good air circulation around plants to prevent fungal diseases, which can be more prevalent in the cooler conditions of fall if overwatering occurs.
Lawn Care
For those with lawns, September is a good time to rejuvenate:
- Aerate the Lawn: If your lawn is compacted, consider aerating it to improve root growth and water absorption.
- Overseeding: This is an ideal time to overseed cool-season grasses such as ryegrass. It will have time to germinate and establish before the cooler winter months.
Harvest
With cooler temperatures, September is also a time to enjoy your garden:
- Harvesting: Keep harvesting summer crops like tomatoes, eggplant, okra, and peppers as they ripen. Enjoy the fruits of your labor and consider preserving excess produce.
September in Tucson offers a unique opportunity to prepare your garden to transition from the hot summer to cooler fall and winter months. By focusing on soil health, adjusting watering practices, managing pests, and planning for the cool season, you can ensure a thriving garden. Embrace the changing season with these gardening tips to keep your Tucson garden lush and productive.
Happy gardening!