Weeds with blue flowers are some of the prettiest weeds you’re likely to find growing in your yard.
But it’s a good idea to identify them so that you know what you’re dealing with. Then you can take appropriate action to control the spread of the weeds. And eliminate them if you prefer.
So, I’ll show you the most common types you’re likely to find encroaching on your garden. And fill you in on the plant details that you need to know.
Let’s dive in!
8 Weeds With Blue Flowers
Weeds with blue flowers are some of the most attractive types of weeds. Here’s how to identify the most common types:
Asiatic Dayflower (Commelina communis)
As the name suggests, the Asiatic dayflower is a native of East Asia and the northern area of South East Asia. It was originally introduced to North America as an ornamental plant. But it’s now considered an invasive weed in many areas.
Asiatic dayflower is an annual weed. And when it first emerges in the spring, it resembles a grass-like weed with wide leaves. The leaves grow alternately along the stem typically reaching between 2-4 inches long, with no petiole and smooth edges.
At the base of each leaf is a sheath attached to the stem. Both the stem and the leaves are hairless. And the stems can grow up to 3 feet long and have bumpy nodes.
The weed flowers from July through to September. Producing clusters of tiny bright blue flowers in the leaf axils at the end of the stems. With each flower only lasting for a day.
The flowers of the Asiatic dayflower have 3 petals — 2 large blue petals and 1 small white petal. There’s also a species of dayflower that has 3 blue petals — the spreading dayflower (Commelina diffusa L.).
The dayflower can grow erect. But usually, this weed creeps along the ground. Rooting at the stem nodes where they touch the soil. The weed grows well in both shady and sunny areas of your garden. Preferring moist and rich soil.
It can be difficult to get rid of this weed. The seeds can remain dormant in the ground for up to 4 ½ years before germinating and sprouting. And the weed is resistant to many weed killers, making it a challenge to control.
Green Alkanet (Pentaglottis sempervirens)
Green alkanet is a common perennial weed. Because it’s an attractive wildflower, some people choose to plant it in their garden. But it can spread quickly in moist soil and shady areas. And it can be problematic to get rid of, so many people consider it an annoying weed.
Green alkanet is a weed with blue flowers that’s in the Boraginaceae family and resembles borage and forget-me-not. The plant flowers from April to June. Producing blue 5-petalled flowers with a white center that grow in clusters on long flower stems.
Green alkanet can grow over 3 feet tall. And has big, egg-shaped leaves that grow up to 16-inches long. The leaves grow alternately and are connected to the stem by long petioles. All parts of the weed are covered in stiff hairs.
Green alkanet roots grow thick and deep. And because the tap root is brittle, it often breaks when you try to pull the weed from the ground. This is a problem because green alkanet can regrow from any part of the roots that you leave in the soil. So take care when removing this weed.
Common Forget Me Not (Myosotis sylvatica)
Forget-me-not is best known for its clusters of small light blue flowers with a bright yellow center. The flowers are funnel-shaped and have 5 petals and 5 stamens.
Forget-me-not is popular with some gardeners because of its pretty appearance. And it’s often deliberately cultivated. But you have to be very careful. Because the common forget-me-not can easily grow out of control, and make you wish you’d never planted it in your garden.
In some US states, common forget-me-not is a noxious and invasive weed. It’s a very fast-spreading plant when the conditions are right. And the weed thrives in wet gardens in locations with a cool summer climate.
Forget-me-nots are self-seeding. And the seeds can lie dormant in the soil for up to 30 years before germinating. The weed also spreads by stolons. And it can be very difficult to eradicate it from your garden if you leave the weed to grow. You can hand-pull forget-me-nots, but the weed will grow back unless you get rid of every bit of the roots.
Forget-me-not flowers are edible. You can try the small blue flowers in a salad or as a garnish on your dinner plate.
Borage (Borago officinalis)
Borage is a plant in the Boraginaceae family, the same as forget-me-nots. It’s an annual weed that flowers in the summer producing clusters of star-shaped, bright blue flowers. The flowers have a cone that sticks out from the center and black-purple stamens.
Borage is a tall and somewhat gangly weed. When fully grown the plant can reach 3 feet in height. Large oval or egg-shaped leaves grow up to 30 cm long and 20 cm wide. And are covered in a prickly fuzz. The greenish-gray stems of the plant are also prickly.
Borage is a prolific self-seeder. And the weed can spread quickly, easily escaping gardens in which it’s cultivated. It grows best in moist, well-drained soil and full sun. But this weed can thrive in a range of conditions. And will grow in dry, nutrient-depleted soils and partial shade as well.
Because this weed has prickly stems and leaves, you should use a thick pair of gardening gloves before trying to remove the weed by hand.
Blueweed (Echium vulgare)
Blueweed is also known as viper’s bugloss. The plant is native to Europe and temperate Asia. And it’s an introduced species in North America where it has naturalized.
Blueweed flowers between May and September in North America. To begin with, blueweed has pink flowers. But as the plant matures the flowers turn blue. The flowers are funnel-shaped and grow in a branched spike and have large protruding stamens.
Blueweed is a large weed that grows up to 3 feet tall. The plant has lanceolate leaves. And both the stem and the leaves are covered with spines, similar to a cactus. You have to be careful when handling this prickly weed or trying to pull it out of the ground, making sure to wear gloves.
The weed grows in a variety of soil conditions. But tends to thrive in sunny locations and doesn’t like the shade. You might find this weed growing on your lawn. And it’s also common to see blueweed growing along roadsides and in fields and pastures. Some people cultivate blueweed as an ornamental plant.
The weed is toxic to horses and cattle when eaten.
Carpet Bugleweed (Ajuga reptans)
Carpet bugleweed is a broadleaf perennial ground cover. As the weed grows, it forms a dense mat of dark green leaves with beautiful clusters of blue flowers. The plant blooms in early May to mid-June, with flowers that grow in 6-inch spikes.
Bugleweed is a creeping weed that spreads by stolons. And it thrives in moist soil. Sometimes becoming invasive in well-watered lawns. But the weed is adaptable and will also grow in moderately dry soil. The plant can grow in all light levels. But it grows best in partial shade.
Spiked Speedwell (Veronica)
Speedwell is one of the most common flowering weeds. It’s well-known for its tiny blue flowers. There are many varieties of speedwell that produce the same distinctive flowers. But as the name suggests, when spiked speedwell blooms you’ll see the tiny, star-shaped flowers clustered around the end of the stem in a highly visible spike. The plant begins to bloom in late spring/early summer and continues until late summer.
Speedwell is a tall weed that grows up to 36-inches. And the leaves are lance-shaped and narrow, growing to around 2-inches long. The leaves grow in pairs and have scalloped edges.
Speedwell enjoys growing in full sun and well-drained soil. And this weed quickly spreads to take over your lawn. Practice good lawn care and maintain a thick and healthy turf to keep it out.
Depending on the variety, you can also find speedwell plants with pink, purple, or white flowers.
Common Chicory (Chicorium intybus)
Common chicory is a perennial weed that’s easily recognized by its distinctive bright blue flowers. The plant flowers between June and the fall up until the first frost arrives. The flowers each consist of numerous florets. And grow on branched stems with clusters of 1-5 flowers growing along the branches or at the tip.
In the early stages of development, common chicory resembles a dandelion plant. It has a rosette of lanceolate leaves that grow between 3-10 inches long. The leaves vary from deeply lobed to irregular tooths. And they can be either hairy or smooth.
Common chicory is often seen growing along roadsides. And you’ll also see it growing wild in abandoned fields, waste grounds, and other disturbed sites. It’s also quite common to find this broadleaf weed invading poorly maintained lawns.
Chicory leaves are edible. And make a good addition to a salad. You can also grind the root and use it instead of coffee as it has a similar flavor.
How Do I Get Rid Of Blue Flower Weeds?
The best way to get rid of blue flower weeds depends on how quickly you identify the weed and take action. If you catch the weed before it spreads, and you only have a small number of plants to remove, you can often pull the weeds out by hand or dig them out using a garden shovel. But you have to be careful when removing garden weeds, as they often regrow from pieces of root left in the ground.
If the weeds have already spread across your lawn or garden, digging them out might be impractical. Instead, you can use a good selective weed killer that won’t harm your grass.
Are the weeds with blue flowers growing in an area where you don’t want anything to grow? If so, then you can use a non-selective weed killer for big areas.
Unfortunately, by the time you find the weeds they might have already spread seeds around your yard. In this case, it’s a good idea to use a pre-emergent herbicide to prevent the seeds from germinating. It’s usually best to apply pre-emergent herbicide to the ground in spring. This will cut down on the amount of weeding you have to do.
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