A lush, green lawn doesn’t happen overnight. It takes immense hard work and time for gardeners. And a significant part of maintaining a great lawn is keeping it weed-free.
A small weed generates more new plants over time, gradually overtaking the entire lawn. So it’s necessary to spot and eradicate the weeds quickly before they suppress the desirable plants in your property.
Pulling weeds is the most irritating task that lawn owners have to encounter. Weeds can dramatically invade the usual tan-colored landscapes blooming in Arizona’s desert climate.
Thus, they are a big nemesis of Arizona’s homeowners. In the worst scenario, weed-overgrown business landscaping is considered a reflection of the business’s product quality.
Lawn weeds can crop up anywhere, be it grass or desert landscaping. This article lists some of the most common weeds to chase down in your Arizona lawn.
5 Most Common Lawn Weeds of Arizona
Weeds are an eyesore for gardeners due to their destructive nature. They battle with other desirable plants in a lawn, robbing their nutrients, light, and more. So eradicating them immediately is a must!
Interestingly, each weed type may seek different approaches to eradication. Thus, it is essential to identify the weed species germinating in your garden. Let’s get started!
1. Barnyard Grass
| Scientific Name | Echinochloa crus-Galli |
| Family | Poaceae |
| Common Names | Barnyard millet, Cockspur, Cockspur grass, Water grass, Japanese millet, Common barnyard grass. |
This summer, annual grass is a common invader of lawns throughout Arizona. They are sprawling, purple-tinged, and coarse grassy weeds with flat blades with a clear vein in the middle. Barnyard grass loves nutrient-rich, moist soils like those found in garden beds and lawns.
Barnyard grass can grow rapidly, consuming the important nutrients like phosphorus, nitrogen, and potassium from the soil necessary for healthy growth.
Moreover, they are a self-pollinating and copious seed producer. For example, each plant can produce nearly 40,000 seeds. And these seeds help this grassy weed to reproduce.
How To Identify Barnyard Grass?
One of the key traits that help in identifying this weed is its first leaves. Firstly, they are hairless, and secondly, there are no membranes or ear-like projections at the leaf’s base. Instead, they are flat, whitish collars without any membranes or hairs.
Next, the leaf buds emerge as rolled instead of being folded. They even have no hairs, but you can often find a maroon tinge at their base. However, the midrib is lighter, clear, and a bit keeled beneath the leaf at the base.
On the other hand, mature plants show rolled leaves with no membranes or ear-like projections at the base. They are even hairless, but you will see only a few hairs at the base. Leaves measure about 5-20mm wide and 10-20cm long.
Barnyard grass is usually a sprawler, but it can be upright, too, based on its habitat. The external stem layer or sheath is typically smooth and appears maroon at the base. However, you can even spot them by their broad, smooth, and whitish mature plant collar. Flowers start blooming in July and continue till September.
The plant has a bulky seeding head with spikes of flower set, appearing closely and in a herringbone pattern. You will find tiny, bristly, purple to green colored flowers, often with a long bristle. On the other hand, seeds appear brown to tan, shiny, and oval.
The best way to prevent this grass from overtaking your lawn is by nipping it in the bud stage in the early summer.
Also Read: Weeds in Nebraska: A Complete Identification Guide
2. Wild Oat
| Scientific Name | Avena fatua |
| Family | Poaceae |
| Common Names | Wild oats, Spring wild oat, Common wild oat, Oatgrass, Folle avoine, Wheatgrass, and Poor oats. |
Next in this list is ideally the most serious grassy weed, responsible for substantial yield losses – wild oats. While this weed robs moisture, nutrients, and light, they cause massive yield losses by nearly 80%.
Wild oats can grow up to 9 inches tall and have characterizing flowing bristles at the top. They are even covered with rough blades throughout.
Wild oats are considered noxious also because they host various cereal diseases like stem nematodes and cereal cysts. These invaders can pop up almost anywhere as they need just a little water to germinate. Moreover, they can quickly become resistant to herbicides, making wild oats more challenging to control.
How to Identify Wild Oats?
Wild oats seedlings have no auricles but display a counter-clockwise leaf twist. The leaf margins have hairs and a membranous ligule. Leaves are dark green and rough because of the small hairs.
However, the youngest leaf is rolled. When this annual weed matures, it develops erect and smooth stems that can reach up to 4 feet in height.
You will find loose, open panicle inflorescence bearing 2 to 3 flowering spikelets that hang from long stalks. The panicle has spreading branches and measures 10-40 cm long and 20cm wide.
On top of that, spikelets have narrow lance-shaped glumes holding 2- 3 florets. However, every 2-3 florets show an oval abscission scar at the base.
The panicle can range from brown, black, and yellow to white and grey, enclosing nearly 250 seeds. You will find hairy seeds at the base that stay dormant for 7 to 8 years in the soil.
However, most seeds sprout within two years. Interestingly, seeds can lose dormancy in dry, warm, and fall conditions but become dormant again in low temperatures and moist soil conditions the following spring.
You can differentiate wild oats from barley and wheat by looking for the presence or absence of ear-like projections or auricles at the junction of stem and leaf. Wild oats don’t have auricles, but barley and wheat have.
Overall, remember that wild oats are resistant to herbicides, making them a serious issue. So look out for them to prevent their growth at an early stage.
Also Read: Weeds in Maryland: A Comprehensive Guide to Identify the Weeds
3. Johnsongrass
| Scientific Name | Sorghum halepense |
| Family | Poaceae |
| Common Names | Aleppo milletgrass, Aleppo grass, Janli-jowar, Chinna, Baru, Impi jola, Jowar. |
Johnson grass is one of Arizona’s most dangerous weeds that can reach up to 7 feet tall. Large stems anchor this weedy plant to the soil, extending nearly 3 feet underground.
They can impose a devastating effect on agriculture. Moreover, their grains can stay asleep for many years and germinate later under preferable conditions.
More significantly, what makes johnsongrass a tough weed to control is that it releases a poison when one interrupts its growth path. It contains the chemical ‘glycosides’ whose concentration significantly elevates when it grows after drought.
As a result, this weed invades agricultural lands rapidly, causing substantial losses. Besides, johnsongrass can harbor diseases and pests that affect crops like maize and sugarcane.
Furthermore, it bears mild allergen pollens, and large infestations enhance its fire risk.
How To Identify Johnsongrass?
This perennial grassy weed is characterized by many upright flowering stems emerging from wide rhizomes beneath the soil. Johnsongrass has hairless leaves with a visible white midrib ranging up to 2cm in width. In addition, they have long hairy membranes where the leaf blade connects the stem.
Stems are unbranched, often with prop roots, and color ranging from purplish to green. However, a central stem with branches and branchlets composes the seedhead about 10-35cm long. They even have spikelets in triplets or pars at their ends, and one will bear the seed.
This weed is self-fertile, producing a prolific amount of seeds that can remain viable in the soil for at least seven years.
You will find oval, reddish-brown, and finely lined seeds of 3 to 4mm. Rhizomes in roots help in spreading the seeds over short distances. Interestingly, seeds help this weed to survive in adverse conditions. And rhizomes can regrow even after flooding and fires.
However, IPM measures might be necessary to complete the prevention or control of johnsongrass’ growth.
In case of small infestations, you can use your hand to pull out the plants. But make sure you eliminate the rhizomes, too, and then burn them so that their parts don’t come in contact with soil.
Also Check: Weeds in NC | Spot 6 Common Weeds With Pictures
4. Red Sorrel
| Scientific Name | Rumex acetosella |
| Family | Polygonaceae |
| Common Names | Horse sorrel, Sheep sorrel, Mountain sorrel, Field sorrel, Sour dock and Cow sorrel. |
Spade-shaped leaves and red flowers characterize this perennial weed. Red sorrel produces abundant pollen that can cause hay fever.
However, some homeowners cultivate this weed as an herb as red sorrel is edible. But although it is safe for human consumption, red sorrel is poisonous to livestock.
This plant thrives in nutrient-deficient and acidic soils. So if you see red sorrel invading your property, analyze your soil. Post-emergent herbicide application is practical during the seedling to the flower-growth stage.
How To Identify Red Sorrel?
Young cotyledons have oblong, dull, hairless leaves fused at the base. They are 5 to 10mm long and display alternate arrangements along the stem. Moreover, the first leaves are egg-shaped, while the latter are arrow-shaped. The basal lobes spread outward.
Mature plants characterize thin stems growing upright from the crown. Lower leaves have longer stalks and basal lobes, appearing as an arrowhead.
In addition, red sorrel has hairless leaves emerging alternately to one another close to the plant’s base. It can grow up to 1 to 1/3 feet tall.
On the contrary, you will sometimes see lance-shaped, stalked, or linear upper leaves. A membranous sheath encircles the stem at the leaf’s base.
However, looking at arrow-shaped leaves and creeping roots, you can differentiate red sorrel from the curly dock. They even don’t have projections or teeth on the flowering parts.
Flowers appear from March to November in clusters on a branching stalk. They are three-sided, egg-shaped, and glossy.
In the early stages, the red sorrel shows yellowish-green flowers that become reddish with time. However, the reddish-brown flowers enclose tiny, single-seeded fruits measuring 1.5mm long.
Using a potato fork or shovel, you can dig out small patches of red sorrel from flower beds and gardens. Then, ensure you have removed the rhizomes. Selective herbicides are even out there to control red sorrel.
5. Redroot Pigweed
| Scientific Name | Amaranthus retroflexus |
| Family | Amaranthaceae |
| Common Names | Redroot amaranth, Rough pigweed, Careless weed, Common tumbleweed, Pigweed amaranth, and Red-rooted pigweed. |
Another common, widespread weed in Arizona is redroot pigweed. This weed sustains in fertile, sunny conditions common in agricultural fields. The stem is upright, reaching up to 1 to 6.6 feet in height. Redroot pigweed tolerates drought, hot weather, and high-nutrient soil conditions. Moreover, they can elongate their stem to avoid shading.
Redroot pigweed is a prolific seed producer, and its seeds help reproduce. You can control pigweed varieties through flame weeding, manual removal, and timely cultivation. Other measures include mulching, stale seedbeds, crop rotation, and cultivating competitive cash crops.
How To Identify Redroot Pigweed?
Redroot pigweed features narrow cotyledons with a sharp end. The upper surface is reddish to dull green, up to 12mm long, and bright red below. Moreover, seedlings have light-green and hairy stems.
Plus, they have egg-shaped and alternate young leaves. Leaves are sparsely hairy on the veins and margins and have wavy margins. They have hairy and purplish petioles.
Mature plants even have alternately arranged leaves with wavy margins. The shape ranges from rhombic-ovate or ovate. In addition, the upper surface is green, whereas it’s hairy beneath.
The lower leaf surface has predominantly white veins. However, the stems are stout, and the lower part is thick and smooth. But the upper part is branched and hairy.
Redroot pigweed has small greenish flowers emerging in stiff and dense terminal panicles. However, small flower clusters appear in the lower leaves’ axils. Overall, a mature stem can grow up to 6.5 feet tall but is typically smaller.
This weed has separate male and female flowers. Interestingly, the male flowers die off after the plant sheds the pollen. Thin-walled fruit contains one glossy brown or black seed. Seeds can sprout in adequately moist soils during the growing season.
Redroot pigweed germinates mostly during late spring or early summer but can sporadically grow throughout the growing season. Each plant produces more than 100,000 seeds that can stay viable, passing through animal digestive tracts. However, a seed can thrive in the ground for nearly 20 years.
But once established, they become hard to eliminate. Thus, it would be best if you aim to prevent their establishment. In addition, cultivation minimizes the durability of pigweed seeds.
Conclusion
When controlling yard or lawn weeds in Arizona, it is about correctly identifying them and then controlling them with pre-emergent treatments.
This will help you to opt for specific treatment measures to eliminate them. After all, you can’t keep guessing the weed species intruding on your lawn. It will only make the issue worse.
To learn about some of the common lawn weeds of Arizona and implement a specific treatment plan.
