Healthy & Beautiful Gardens – Plants to avoid

Hello, Fellow Gardeners! As a change from my usual weekly format of telling readers what to do in the garden, this week I’d like to discuss what not to do in the landscape. Just as most artists and designers know, it’s not just what is put into the garden that makes it special, but also what is left out of it.

Let’s discuss those plants that are considered undesirable in the area. Keep in mind though, some of them are wonderful in the right spot. As the saying goes, “A weed is just a plant in a place where it’s not wanted.”

On the top of my list of plants to be aware of are trees with invasive roots. Why? Those who have ever dealt with one they will already know the answer. They can take over most of the front or back yard in a typical residential lot.

Trees that are typically planted in lawns never seem to get that deep watering that trees need in order for their roots to go deep. Instead the water is mainly at the surface [sprinklers] so that’s where the roots are. This is not good since they are competing with all the other plants and lawn for that water. Since they are bigger, the trees usually win.

Schinus mollis, otherwise known as California pepper tree, has a highly invasive root system. It exudes a substance from its roots that causes other plants to gradually die back. It’s a beautiful tree out on a large estate with nothing to compete with. But, if you do not have a large estate, it’s best to steer clear of this one.

Another variety of this tree, known as Schinus terebinthifolius or Brazilian pepper, is invasive as well and should be avoided. Both of these trees actually come from South America; neither is native to California despite the misleading name.

The black walnut tree falls into the same category as the pepper trees; nothing will grow around one of these well.

Robinia or Locust, a variety I grew out on acreage, was called Purple robe. It’s gorgeous on a very large lot when grown over drip irrigation, but extremely invasive in a lawn or typical residential lot. The plant’s roots throw out suckers that pop up literally everywhere there’s water. Forget about this one in the garden.

Pretty much all varieties of Eucalyptus are out of bounds for the residential lot for numerous reasons. They are messy trees with invasive roots and brittle branches that break off and are high in resins. This is a problem because these resins can be a potential fire hazard. This is not a tree anyone would want around the house.

The California sycamore is a beautiful native tree that grows in riparian areas or those areas with water just below the surface. Put it in the lawn and prepare to do battle! My neighbor had one in his front yard – in the lawn – and he ended up cutting it down. He’s been digging out the huge roots for three weeks now. Not a lot of fun for him.

There are also several species of palms to avoid, most notably the Mexican fan palm.

One shrub to avoid planting on residential sized lots is the Castor bean plant, or Ricinus communis. Not only is this plant invasive, but also very poisonous (enough said). It is spreading throughout the state in riparian areas and taking over from the native plants (many invasive plants are doing this).

Pampas grass or Cortaderia selloana is a giant clumping grass variety that spreads voraciously by seeds and underground rhizomes. It’s on the hit list for the most invasive species in many native landscapes in the state, so keep this one out of the yard. There are many other large clumping grass varieties that behave; Miscanthus would be a better choice than this one.

Although many people love mint, it’s a rampant spreader. It will overrun a place that it likes if it is given moisture and some shade. I will only grow mint in a pot and that is my recommendation to gardeners as well.

Chives are another form of plant that is edible but, if allowed to bloom and go to seed, dozens of plants will begin popping up everywhere. Grow this one in a pot and keep cutting it back, just like basil. Use it without letting it go to seed for as long as possible.

Mexican feather grass, otherwise known as Stipa tenuissima, is a beautiful clumping grass. But you better really love it if you plan to put it in your yard. When it sets seed there will be thousands of seedlings anywhere there is a damp patch of earth. It’s great for an area that gardeners want completely filled in with this plant, but other than that, don’t use it!

Japanese honeysuckle or Lonicera japonica is a rampant grower so just beware of that fact before planting. Halliana is the variety name often seen planted on slopes and the most aggressive. Lonicera periclymenum is a less aggressive species that would be better to use.

I could probably go on here for awhile listing another dozen or so plants I would avoid, but I’m running out of room so I just want gardeners to think about the ultimate size of plants before bringing them into a garden. Also plants like Agaves and cactus – I love them, but gardeners definitely don’t want to locate them near a path, or if there are children or dogs running around. Check out, which is the web site of the California Invasive Plant Council for lots more information on what not to plant.

Just a reminder, California is in a drought, so watch those sprinklers. Eastern Municipal Water District is paying $2 a square foot to remove lawn and replace with drought tolerant landscaping. As always I am available for consultations and design work. Have a great week!

Linda McDonald is a landscape designer with Unique Landscapes and can be reached by calling (951) 764-4762 or by visiting

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