What Invasive Species Should You Avoid in Your Southern California Yard and Garden

Written by Kelsey W.

If you take a stroll down any neighborhood street in Southern California, you’ll see all sorts of beautiful plants, many of them unusual and exotic. Some of those plants were probably brought into the region from other countries that have similar growing conditions as SoCal, making them feel right at home when planted in someone’s front yard.

Unfortunately, some of those species aren’t the healthiest additions to Southern California yards because they’re considered “invasive” and don’t play nicely with native species. While it’s usually fine to enjoy a beautiful exotic houseplant on a shelf in your home, it’s often not advisable to put non-native species in your yard where they can spread and take over the homes of native plants.

Fortunately, due to the hospitable weather of Southern California, it’s incredibly easy to find beautiful native plants – all sorts of them in all kinds of colors, sizes, and appearances – to fill your yard with colors and life throughout the year. To ensure the native plants you choose for your yard stay safe from non-native plants, endeavor to keep the following invasive species out of your yard.

The Tree of Heaven is Not So Heavenly

One of the biggest gardening mistakes people made during the famous Gold Rush of the 1800s in California was bringing the Tree of Heaven or “Ailanthus altissima” to the state. The plant grows swiftly and has a true knack for crowding out native plants. Additionally, and most impressively, it releases harmful chemicals into the ground that work to kill other species around it, so it can have room to spread.

One of the ways it spreads is when it’s cut down but not removed by the roots. When it’s simply chopped, the plant takes that as a signal that it’s under attack and it starts to spread underground, sending up new shoots all around to overwhelm the area and ensure its survival. The only way to get rid of the plant and all its offspring is to remove the taproot, which is no small feat if it has a chance to get established.

Greater Periwinkle Is a Little Too Great

Owing to its pretty purple flowers and its ability to make any garden beautiful, greater periwinkle or “vinca major” is a little too good at its job, often pushing out any other plants in the vicinity and taking over the area with gusto.  Although it looks beautiful covering the ground, it tends to spread with wild abandon into other yards and areas.

It’s always best to avoid using this plant in your garden, but you should also remove it if it’s already planted somewhere around your home. Even though it’s beautiful, there is enough of this particular plant growing in its homeland of the coasts of Mediterranean France and Spain, as well as much of western Asia and northern Africa. For a beautiful alternative, try Texas frog fruit or “Phyla nodiflora,” a creeping groundcover with white and purple flowers.

Mustard Plants are Great for Eating But Not for California Yards

Mustard greens are a popular part of backyard gardens, offering a tangy and delicious bonus to your salads, but several types of invasive mustard plants do quite a bit of damage to the landscape when they’re allowed to grow with wild abandon. Like the tree of heaven plant, mustard plants like black mustard or “Brassica nigra,” will mess with the soil around them, so other plants have a rough time growing.

The good news is that you can eat the mustard greens you pull out of the ground. The bad news is that you probably shouldn’t plant any additional mustard plants because they can take over an area and spread far and wide, taking over all the available growing space. Instead of growing a mustard plant, try growing golden yarrow. The small ground cover will give you all the little yellow flowers you can handle.

Spanish Broom is Beautiful but Not for SoCal Gardens

The Spanish broom plant originally hails from the Mediterranean and other nearby continents like Asia and North Africa. Settlers in California brought broom plants in the middle of the 1800s to beautify their gardens, as well as to prevent soil erosion. Unfortunately, the plant is a terrible addition to SoCal’s fire-prone environment due to its propensity for creating dry brush and dense areas that feed wildfires.

It’s always best to remove Spanish broom when you find it, particularly if your home sits in an area where wildfire is a concern. Although the plant has beautiful flowers and makes a nice visual addition to any SoCal garden, the fire risk just isn’t worth it – and the plant does spread fast, too, crowding out natives. Instead, consider the California flannelbush or ” Fremontodendron californicum,” which also produces bright yellow flowers.

Iceplant Seems Like a California Native, But It’s Not!

Iceplant is so incredibly common across California, and especially Southern California, that you might think it’s a native plant that’s always been here. However, iceplant is very much an invasive plant that’s actually from the coast of South Africa rather than the California coast. It’s been used in SoCal for more than a century to prevent erosion, but it also tends to take over the environment and prevent native plants from thriving.

The one good thing about iceplant is that it’s not difficult to remove. It doesn’t have deep roots, so it’s pretty easy to pull up as long as you grab it close to ground level. The perfect replacement for iceplant is California lilac or “ceanothus,” which is also a super choice because it needs zero attention in the summer when water is scarce, and the need to conserve is at its highest. They only need attention as they’re getting established and are entirely self-sufficient once mature.

Stop Onion Grass Before It’s Too Late!

The Australians consider onion grass or “Romulea rosea” a noxious weed because it’s so harmful to the local ecology and livestock in that country. This South African plant has the ability to take over entire pastures and sicken some farm animals like sheep. Unfortunately, it’s starting to become a known weed in the United States, too, where it has the potential to become a big problem if it’s allowed ot proliferate.

The plant is quite beautiful with its light purplish-pink flowers and their delicate pointed petals, but the last thing anyone should do in Southern California is plant onion grass because it’s beautiful. It’s important to avoid this particular plant entirely to safeguard SoCal gardens and animals. A suitable alternative is the California native “Corethrogyne filaginifolia” or California aster, which is a lovely plant with little pink flowers that sort of look like daisies.

Don’t Let Russian Olives Crowd Out Native Species

The Russian olive tree or “Elaeagnus angustifolia” does a great job at stabilizing soil and acting as a windbreak, but it’s also way too effective at spreading and crowding out native plants. The plant is native to Europe and Asia and was brought to the United States in the early 1900s. It’s become such a menace that it’s considered invasive in more than a dozen states throughout the American West.

Unfortunately, Russian olives are difficult to control because they form deep roots and can grow again even if you chop them down to the root crown. It’s important to cut these trees out early before they have a chance to become established. A tree that will play much more nicely with the environment is the valley oak or “Quercus lobata,” which is a wonderful shade tree and native of California. It can grow up to an amazing 100 feet tall!

Find Native Plant Species for Your Home at Green Thumb Nursery

Create a native plant paradise at your home with help from Green Thumb Nursery. You’ll find everything you need to create a beautiful yard and home at a Southern California Green Thumb Nursery location. Figure out the best way to grow happy plants that love the California sunshine and live harmoniously in any SoCal yard, porch, or patio.

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