It’s finally fall in Arizona, which means cooler temperatures and more time spent outside. Unfortunately, this usually signals the beginning of weed season. While your yard gets a break from the intense summer heat, weeds tend to take advantage of the cooler weather and start popping up.
The best way to keep weeds under control is to get ahead of their growth. In this blog, we will share some of the most common weeds Arizona homeowners can expect during the fall and what you can do to control them.
Why Do Weeds Appear in the Fall?
Arizona weeds appear in the fall because the cooling temperatures and seasonal moisture trigger winter weeds to germinate while summer weeds are more noticeable as they change color.
As the daytime heat breaks and soil temperature cools, dormant seeds from weeds like Poa Annua (Annual Bluegrass), London Rocket and Cheeseweed Mallow start to wake up. The moisture from monsoon season leaves behind deep soil moisture/humidity, providing the perfect hydration needed for these seeds to grow quickly. Also, late summer and early fall haboobs and high winds carry fresh batches of weed seeds and redistribute them into nearby gardens.
The good news is summer weeds like crabgrass and foxtail tend to start dying as daylight shortens. The bad news is they begin to turn purple, yellow or brown, which makes them stand out more, especially against green lawns and plants.
Most Common Fall Weeds in Arizona
1. Annual Bluegrass
Annual Bluegrass is a cooler-season grassy weed that appears in lawns, gardens and landscaped areas. It grows in small clumps and is usually easy to spot because of its bright green color. Since Annual Bluegrass produces seeds quickly, getting control of it early is important. A pre-emergent applied before germination can help prevent it from becoming established in your yard.
2. London Rocket
London Rocket is one of the most common weeds found throughout Arizona. It has jagged green leaves, and if allowed to grow, it will begin blooming small yellow flowers. You may recognize it taking root in yards, along sidewalks or gravel areas. Removing the London Rocket while it is still young can help prevent these weeds from flowering and producing more seeds.
3. Cheeseweed Mallow
Cheeseweed mallow is a broadleaf weed that develops rounded leaves and a deep taproot. Once fully grown, that root makes the weed difficult to completely remove by hand. If you remove cheeseweed by pulling on it, make sure you do it early on. A more established weed may require a post-emergent.
4. Rescuegrass
Rescuegrass is yet another grassy weed commonly found in Arizona during the fall. When temperatures are cool and moisture is available, it can grow rapidly. Like other annual grasses, rescuegrass is easier to manage before it becomes fully established. Pre-emergent products can help prevent seeds from germinating, while already existing weeds may need a post-emergent treatment.
5. Sow Thistle
During fall in Arizona, sow thistle is another broadleaf weed that appears. It has jagged leaves and yellow flowers that look like dandelions. This weed spreads through seeds, so controlling it before it grows flowers helps prevent future growth. Small weeds can often be pulled by hand, but if left to grow, the larger weeds may need additional treatment.
Pre-Emergent vs. Post-Emergent Weed Control
The most important part of controlling fall weeds is choosing the right treatment. Pre-emergents are designed to prevent weeds from getting established. They work best when applied before weeds begin to grow. After applying to the areas in the yard where weeds are commonly found, many pre-emergents need to be watered into the soil to create a protective barrier.
Post-emergents target weeds that have already shown up and are actively growing. Knowing when and how to use post-emergent herbicides can help improve the effectiveness of treatment. Using the right product largely depends on the type of weed and where it is growing.
The first step is to identify the weed. If you are unsure, we recommend bringing in a photo and showing it to one of our in-store experts. They can then help determine the best course of action for removal. You may need to use a combination of products and approaches depending on the situation. Our Bug & Weed Mart managers will also provide easy-to-follow instructions for addressing and treating the weed growth and the area you are treating.
Desert Landscaping
Desert landscaping is not immune to weeds. While lush yards and gardens may seem more prone to weed growth, many unwanted weeds will appear through gravel, rock and other desert landscaping commonly found around Arizona homes.
Weeds that repeatedly appear in gravel beds or other areas may be a sign of underlying moisture or soil conditions. If weeds keep growing back in the same spots, look at what’s feeding them: leaking irrigation, overspray, pooling water and bare soil all create the moisture and open ground weeds need to take hold.
DIY Weed Prevention
Before applying a weed control product, clean the area by removing any existing weeds. Treating the soil before seasonal weeds emerge makes it easier to maintain rock and gravel areas throughout the fall and winter. Pay extra attention to areas where water collects, as extra moisture creates the ideal environment for weeds to grow. If you take these steps, you can minimize the time and money you’ll need to spend keeping your garden free of weeds.
Beat Unwanted Fall Weed Growth
Remember that getting started in early fall can save you from the need to pull weeds in the coming months. Identify weeds early and use the appropriate treatment for your landscape. To learn more about the best products to use and how to apply them, visit a nearby Bug & Weed Mart and speak with an expert for instructions and guidance.