18 Weeds with Yellow Flowers: Identification and Control

What counts as a weed is largely subjective. The ‘official’ definition of a weed is a plant growing where it shouldn’t be. But most of us gardeners use the term to describe plants that like to invade our lawns and gardens and/or outcompete more desirable species.

In the same vein, not all weeds are unattractive. Many have pretty flowers that rival our favorite garden plants. (Countless weeds were first introduced as ornamentals before we knew how aggressively they would spread.)

This article features the most common weeds with yellow flowers you might find in your home landscape. I’ve also included some expert tips for easily identifying and controlling these species.

18 Yellow Flowering Weeds To Watch Out For

As you work your way through this list, note that I’ve highlighted a few key traits of each weed. These include:

  • Weed type — This tells you a bit about the weed’s general growth habit as well as what kind of chemical treatment (if one is deemed necessary) will be most effective.
  • Life cycle — Annual, biennial, and perennial weeds all call for slightly different control strategies. It’s very important to know which life cycle you’re dealing with.
  • Toxicity — While few weeds on this list are toxic to humans, many are dangerous for pets and livestock. Weeds with high toxicity may require immediate removal if you have animals on your property.

Now, let’s jump right in!

1. Dandelion

Dandelion
  • Taraxacum spp.
  • Type: Broadleaf
  • Life Cycle: Perennial
  • Toxicity: None

Dandelions are tough and grow all year, but they’re most visible in spring and fall. While maligned by many homeowners, the flowers offer a vital food source for bees and other insects when only a few other plants are in bloom. 

Unfortunately, dandelions also spread quickly via wind-dispersed seeds and can take over a yard within a single season.

To keep dandelions under control, cut your lawn often whenever they’re in bloom. This stops them from producing more seeds. Individual dandelions can be pulled out by hand. Using a narrow spade to get out the whole taproot works best.

2. Bird’s-foot Trefoil

Bird’s-foot Trefoil
  • Lotus corniculatus
  • Type: Broadleaf
  • Life Cycle: Perennial
  • Toxicity: Low

Bird’s-foot trefoil is a common weed in lawns and other open areas. Its seed pods look like birds’ feet (which explains the name), and it has trifoliate leaves similar to clover. The yellow flowers look like those of pea plants.

Some types of bird’s-foot trefoil grow upright. Others spread along the ground. The low-growing types can be tough to control in lawns if they sit below your mower blades.

To control bird’s-foot trefoil, cut the plants low to the ground to prevent them from producing more seeds. You can also hand-pull this weed, but the root system can resprout if not completely removed.

3. Yellow Woodsorrel

Yellow Woodsorrel
  • Oxalis stricta
  • Type: Broadleaf
  • Life Cycle: Annual or perennial
  • Toxicity: Moderate

Yellow woodsorrel, or yellow oxalis, can grow just about anywhere, even in small cracks in the pavement. Like other types of shamrock, it has heart-shaped leaves that fold up at night or when the plant is stressed.

One reason yellow woodsorrel is so widespread is that its seed pods ‘explode’. This scatters the seeds as far and wide as possible.

Regular mowing and mulching can help reduce the number of seeds that get into your yard. Pulling woodsorrel out by hand can work if you get the whole plant. Using a pre-emergent herbicide is what works best in my own garden.

4. Wild Parsnip

Wild Parsnip
  • Pastinaca sativa
  • Type: Broadleaf
  • Life Cycle: Biennial
  • Toxicity: High

Wild parsnip is a biennial weed that’s often found in meadows and along roadsides. It usually blooms in the summer of its second year.

Its leaves are similar to a carrot’s. The umbel-type flowers look a lot like Queen Anne’s lace but are yellow instead of white.

Although the root is edible, be careful not to touch any part of the plant growing above ground. Wild parsnip contains a sap that causes phytophotodermatitis, or severe skin reactions triggered by sunlight. It’s also poisonous to livestock and other grazing animals.

The best way to control wild parsnips is to remove the flowers before they produce seeds. Always wear gloves and protective clothing when handling this weed.

5. Goldenrod

Goldenrod
  • Solidago spp.
  • Type: Broadleaf
  • Life Cycle: Perennial
  • Toxicity: Low

Despite being native to many regions, goldenrod is often classified as a weed because of how easily it spreads. 

It’s known for its spikes of yellow flowers that bloom in late summer and fall. Goldenrod is very hardy and can handle all different soil and light conditions.

The tricky thing about Goldenrod is that it’s also regarded as one of the best plants for native pollinators. However, in gardens and even some natural biomes, it can be aggressive and crowd out other plants.

6. Common Ragwort

Common Ragwort
  • Senecio jacobaea
  • Type: Broadleaf
  • Life Cycle: Perennial
  • Toxicity: High

Common ragwort is a biennial or short-lived perennial weed. It has yellow flowers similar to a daisy and deeply lobed foliage. It grows in many environments, including pastures, roadsides, and garden beds.

Ragwort blooms from early summer to late fall and produces tons of seeds throughout that time. While it provides food for bees, butterflies, and other insects, it’s highly toxic to livestock like horses and cattle.

Controlling ragwort can be tough because of the sheer volume of seed. If there aren’t many plants, you can pull them out by hand before they make said seeds. For larger areas, cutting or mowing several times a year can help.

7. Cypress Spurge

Cypress Spurge
  • Euphorbia cyparissias
  • Type: Broadleaf
  • Life Cycle: Perennial
  • Toxicity: Moderate

Cypress spurge enjoys dry conditions and most commonly grows in places like lawns, pastures, and roadsides. It has thin, blue-green leaves that look like cypress leaves, and yellow-green flowers that bloom from late spring to early summer.

Originally from Europe and Asia, cypress spurge is now invasive in parts of North America because it grows and spreads quickly. The weed’s sap is toxic to livestock and can cause irritation if it touches your skin.

Wear gloves when pulling cypress spurge to avoid skin irritation. Regular mowing will halt or at least slow down its spread.

8. Purslane

Purslane
  • Portulaca oleracea
  • Type: Broadleaf
  • Life Cycle: Annual
  • Toxicity: Moderate

Purslane thrives in areas with poor, disturbed soil. It has a sprawling growth habit and is easy to ID by the reddish stems and fleshy, succulent-like leaves.

This weed stores large amounts of moisture in its foliage, making it incredibly drought-tolerant. It’s problematic because of the enormous quantity of seeds one plant can produce.

In my experience, purslane is uncommon in healthy garden beds and lawns since it prefers low-quality soils. However, you may find it growing in the cracks of a garden walkway or paver patio.

9. Bitter Wintercress

Bitter Wintercress
  • Barbarea vulgaris
  • Type: Broadleaf
  • Life Cycle: Biennial
  • Toxicity: Low

Bitter wintercress, also known as yellow rocket, is a biennial weed found in fields, pastures, and disturbed areas. It’s particularly noticeable in early spring when it’s one of the first plants to bloom.

From an ecological perspective, bitter wintercress provides an early source of nectar for pollinators emerging from winter hibernation. However, native species of Barbarea are far more suitable for this purpose.

Large-scale control of bitter wintercress is best done by mowing when the weed is in bloom. You can hand-pull individual plants that manage to invade your yard or garden.

10. Mullein

Mullein
  • Verbascum spp.
  • Type: Broadleaf
  • Life Cycle: Biennial
  • Toxicity: Low

Mullein is a biennial weed native to Europe and Asia but is now found in nearly all corners of the world. You’ll most likely spot it in disturbed, open areas like fields, roadside ditches, and livestock pastures. 

During its first year, mullein has a distinct rosette of fuzzy, grey leaves. Plants at this stage are low-growing and very easy to overlook. In the second year, however, a large flower spike (that can grow up to 10 feet tall) emerges from the rosette.

Mullein’s huge size and prolific seed production can make it a nuisance in some landscapes. One of the best strategies is to locate first-year plants and remove them before they can produce flowers.

11. Creeping Buttercup

Creeping Buttercup
  • Ranunculus repens
  • Type: Broadleaf
  • Life Cycle: Perennial
  • Toxicity: Moderate

Creeping buttercup enjoys damp, fertile soils. In other words, it will happily set up shop in your lawn or garden. It will also take root in beaches and other sandy areas.

Don’t be fooled by creeping buttercup’s attractive flowers. It spreads via both seeds and creeping stems and will quickly take over a landscape if left to its own devices.

Controlling creeping buttercup can be a challenge. Hand-pulling is effective as long as you get the entire plant. For larger areas, cut back the stems frequently to prevent seed production.

12. Black Medic

Black Medic
  • Medicago lupulina
  • Type: Broadleaf
  • Life Cycle: Annual
  • Toxicity: Low

Black medic is often mistaken for a type of clover due to its trifoliate leaves. It’s often seen growing alongside white clover (Trifolium repens).

This weed is particularly well-adapted to dry, compacted soil. This makes it a common nuisance in neglected lawns.

According to the University of Wisconsin, the appearance of black medic may also indicate low nitrogen. So simply improving your lawn or garden’s soil quality can go a long way in discouraging this weed.

13. Yellow Nutsedge

Yellow Nutsedge
  • Cyperus esculentus
  • Type: Sedge
  • Life Cycle: Perennial
  • Toxicity: None

Yellow nutsedge is a noxious weed that normally appears in poorly drained soils. Sedges can be differentiated from true grasses by their triangular stems.

This plant loves hot weather and will often outpace turfgrass in terms of summer growth. Many homeowners first notice yellow nutsedge when it suddenly towers over the rest of the lawn.

Nutsedge spreads through an underground network of tubers sometimes called ‘nutlets’. This makes yellow nutsedge very hard to eradicate.

Yellow nutsedge can be a sign that your landscape lacks proper drainage. While hand-pulling and herbicides can be effective, make sure they’re not just covering up a bigger problem.

14. Sulfur Cinquefoil

Sulfur Cinquefoil
  • Potentilla recta
  • Type: Broadleaf
  • Life Cycle: Perennial
  • Toxicity: None

Sulfur cinquefoil enjoys dry, recently disturbed soil. It harms native plants by forming dense colonies that choke out competing species. If that wasn’t bad enough, very few animals utilize sulfur cinquefoil for food.

Each compound leaf has five toothed leaflets that may be mistaken for wild strawberry (a close relative) or even a type of cannabis. Note that there are a few non-invasive types of cinquefoil that also look very similar.

This weed is hard to control without chemicals once established, so be sure to pull plants as early as possible. The entire root crown must be removed to prevent regrowth.

15. Yellow Toadflax

Yellow Toadflax
  • Linaria vulgaris
  • Type: Broadleaf
  • Life Cycle: Perennial
  • Toxicity: Moderate

Yellow toadflax, also known as butter-and-eggs or wild snapdragon, is an example of a weed that was first introduced as an ornamental flower. Even today, some well-intentioned gardeners plant this noxious weed as a wildflower. 

This weed has an extensive, interconnected root system that is extremely difficult to control. Root fragments as small as ½ inches long can sprout into new plants. The USDA recommends cleaning all machinery after mowing or tilling yellow toadflax to prevent the accidental spread of these fragments.

You can remove yellow toadflax by carefully digging out the entire root system. Alternatively, use a combination of cutting back flowers before the seed set and appropriate chemical treatments to control this weed.

16. Spanish Broom

Spanish Broom
  • Spartium junceum
  • Type: Broadleaf
  • Life Cycle: Perennial
  • Toxicity: High

Spanish broom is often found in dry, open areas. It stands out from the landscape with bright green, leafless branches and sweet-smelling flowers that bloom from late spring to early summer.

While the flowers are attractive, Spanish broom crowds out native vegetation and creates a fire hazard due to its high oil content. It’s also toxic to most livestock.

If you live somewhere affected by Spanish broom, you may be required to remove it by law. Cut mature plants to the ground and treat the remaining stumps with a paint-on herbicide. Seedlings are easy to hand-pull.

17. Curly Dock

Curly Dock
  • Rumex crispus
  • Type: Broadleaf
  • Life Cycle: Perennial
  • Toxicity: Moderate

Curly dock is a robust perennial weed with an affinity for damp areas. You may find it invading riparian habitats or over-irrigated landscapes.

This weed can grow up to 5 feet tall and features a deep taproot that helps it survive all kinds of tough growing conditions. The yellow flowers mature into dry, reddish-brown seed pods.

As with most noxious weeds, the sooner you deal with a curly dock the better. If you need a bit of motivation: According to Utah State University, mature plants can produce up to 40,000 seeds per year! Tilling or hand-pulling young weeds before they flower is a very effective strategy. 

18. Wild Mustard

Wild Mustard
  • Sinapis arvensis
  • Type: Broadleaf
  • Life Cycle: Annual
  • Toxicity: Moderate

Wild mustard is an extremely invasive weed commonly found in disturbed areas like roadsides, agricultural fields, and new developments. It typically blooms in late spring to early summer. 

This weed is not just of concern to gardeners and farmers but also poses a risk to native habitats. In addition to growing rapidly and producing tons of seeds each year, wild mustard is allelopathic. This means that wild mustard plants release chemicals that prevent other (beneficial) plant seeds from germinating.

The good news is that, since wild mustard is an annual, mowing down and hand-pulling prior to the seed set are very effective. Large infestations may require chemical treatments before being re-naturalized with native species.

How to Control Weeds with Yellow Flowers

Step one is learning to identify the culprits. Many weeds and desirable plants look alike, so you need to positively ID unwanted plants before removing them. This article should help with that!

Knowing the exact type of weed you’re dealing with is also crucial to effective management. Not all control strategies work equally well on all plants.

I always recommend starting with cultural control strategies such as mulching (to prevent weed seeds from establishing in the first place) and hand-pulling. These practices can make a big difference in the number of weeds invading your landscape without putting other plants or wildlife at risk.

In some cases, herbicides are needed to control invasive weeds:

When it comes to herbicides, most gardeners are familiar with post-emergent weed killers. These products only affect weeds that are actively growing when the chemicals are applied.

Post-emergent herbicides are incredibly effective but should be used sparingly. Always follow the manufacturer’s usage directions for the safety of both you and the environment.

Also, do not just buy the first post-emergent herbicide you see and use it in your lawn or garden. Some active ingredients target all plants equally while others only affect specific types of plants. For example, a homeowner wanting to control dandelions in their lawn would need to use a product that kills broadleaf weeds only.

I personally see great results applying a pre-emergent product twice annually in my perennial beds. Pre-emergent herbicide targets seeds in the soil, impeding germination. Note that these products will affect the seeds of weeds and desirable plants equally.

If you are interested to learn more about yellow flowering plants, here’s a link to Yellow Perennial Flowers.

Citations

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.