Native Ageratum Flowers You Should Plant & Invasive Varieties To Avoid

There are a few different varieties of ageratum, with Wild ageratum, Texas ageratum, and Keys ageratum being native to the United States. These plants can be easily grown in your garden and will provide you with dainty, pretty blooms that last for many weeks. But, there are also a couple of ageratums, commonly known as billygoat weed, that come from South and Central America and are considered a common weed that should be avoided.

Although ageratums are one of the best deer-resistant flowering plants for your garden, it's important to choose the varieties or species that are regarded as non-invasive to limit their spread into other areas nearby. Learning which plants have less chance of becoming aggressive will help to protect natural landscapes such as forests, grasslands, and nature reserves. To that end, you might also want to familiarize yourself with other invasive plants you should never grow in your garden.

Wild ageratum (Conoclinium coelestinum) is native to the eastern U.S. states. It can be distinguished from non-native species by its leaves which are glossy and hairless. It has lovely blue-purple flowers that can last for up to eight weeks. The flowers are full of nectar and enjoyed by pollinators. You can plant this lovely ageratum flower in a sunny or semi-shaded spot, but it does prefer fairly moist soil. Keep in mind that it will self-seed and spread through underground rhizomes, so you'll need to keep it in check.

Texas ageratum (Conoclinium greggii) is another North American wildflower that is native to the southwestern states. This plant also has pretty blue to purple flowers and is loved by butterflies and other pollinators. The plant blooms from mid-summer right into the fall. Texas ageratum can be planted in a sunny spot, but it will tolerate some shade. It prefers drier to medium-moist soils that are well-drained. This ageratum also spreads through underground rhizomes, so you'll need to keep an eye on it so it doesn't take over your garden. It's hardy in USDA zones 7 through 10. Both of these native species can also be grown in containers which is a good way to stop them from spreading throughout your garden. Keys ageratum (Ageratum maritimum) is another native wildflower which is in danger of extinction. It grows naturally around the Florida Keys and is both salt- and drought-tolerant.

While there are around 43 species of Ageratum native to South and Central America, two of these ageratums should be avoided as garden plants. Both are commonly known as billygoat weed, (Ageratum conyzoides and Ageratum houstonianum). These two species are annuals which means that they complete their life cycle in the same year. You can distinguish these weedy species from native ageratums by their hairy leaves and stems, although wild ageratum also has hairy stems but there are no hairs on the leaves.

In particular, Ageratum conyzoides is a prolific seeder and has established itself throughout the landscape, especially around the Gulf Coast. It can often be found as an invader in plant nurseries. If you find this weed either in your garden or in pots that you've purchased from a nursery, keep the invasive plant from spreading by making sure that you dispose of it so that it isn't allowed to flower and set seed. Similarly, if you've purchased one of the hybrid cultivars of ageratum from a nursery to plant in your garden, you can stop it from spreading by removing the spent flower heads before they're able to produce seeds.