Everyone loves a lush, healthy garden, but cultivating one isn’t as easy as it might seem. If you’re a first-time gardener or have little or no knowledge of growing plants, it’s wise to speak to an expert or do a little research before choosing what to plant in your outdoor bed. After all, you don’t want to look down on a garden that ends up being more of a problem than a pleasure.
“It’s a great time of year for gardens, and plants should spring up left, right and center,” says Jo Lambell, founder of Beards & Daisies and author of The Unkillables. ‘But be careful. While some plants may appear showy, they can be invasive or poisonous.”
It may come as a surprise to some, but certain strains can cause hay fever, rashes, hives, and blisters. Some can deplete water levels, crack walls, or even weaken the foundation of your home. Find out which plants to exclude from your garden idea plans with our expert guide.
7 plants to avoid in your garden
For a happy, healthy garden, you need to find plants that give you the look you want and that aren’t likely to cause problems. Usually, popular annuals, perennials, and shrubs are known to trigger more reactions than other plants. Usually pansies, African daisies, nasturtiums, alliums and succulents are easy to grow and safe plants to grow.
That being said, note the plants that are likely to be a cause for concern.
1. Boxwood
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“Boxwood has long been a staple of the traditional garden, used to border beds and pathways and neatly trimmed into pleasing architectural shapes,” say Annie and Jemma Charman, founders of Green Rooms (opens in new tab). “However, in recent years it has been plagued by the boxwood caterpillar, which will quickly devastate the plant, leaving it brown, webbed and beyond salvage.”
One way to tell if the plant is sick, infected, or dead is if the leaves and shoots turn dark brown and begin to shrivel and fall off. This can happen over several months or all of a sudden.
Instead try: Garden trends are moving towards more sustainable plants that are easy to grow and don’t damage the surrounding landscape. “Rather than take the risk, opt for Ilex crenata (Japanese holly) or Pittosporum tenuifolium Golf Ball, both of which have small leaves and dense growth like boxwood and can be neatly trimmed and shaped in the same way,” say Annie and Jemma .
2. Water hemlock
“Some of the most dangerous plants are frustratingly some of the most beautiful,” says Whitney Bromberg Hawkings, CEO and co-founder of FLOWERBX (opens in new tab). Water hemlock (Cicuta), which closely resembles cow parsley, is littered across the landscape the second the sun comes out, but can also be deadly to animals and humans within minutes of ingestion. It contains a highly toxic chemical that is fatal if ingested, not to mention its strong carrot-like odor that makes it a garden foe.’
This plant typically grows in damp, swampy places and is often confused with its non-toxic doubles like wild carrots or parsnips. If accidentally ingested, the symptoms of poisoning are seizures, nausea, vomiting, abdominal pain, tremors, confusion, weakness or dizziness.
Instead try: Consider the water parsnip, which looks similar to water hemlock. This herb with divided leaves and clusters of white flowers can be cultivated for its edible tuberous roots.
3. Japanese Knotweed
“Japanese knotweed is an invasive plant with bamboo-like red shoots and scoop-shaped leaves,” says Stokemont’s Bradley MacKenzie (opens in new tab). “It can grow up to 10 feet tall in spring and summer. But the worst thing about this plant is that its roots can reach up to 20 meters underground.”
“The spread of Japanese knotweed underground could disrupt pipes and drains and weaken building foundations or pavement, leading to collapse of foundations and poor flood protection,” says Bradley. “It is important to check this out immediately and take thorough eradication measures before it is too late. We strongly recommend that you seek professional help when removing them as they easily recover from even the tiniest remnants. If you prefer to do it yourself, pesticide would be the most effective way to kill these zombie-like plants!’
Instead try: Woody shrubs & trees or Houttuynia cordata are great alternatives to Japanese knotweed. The latter is usually grown as a leafy vegetable and used for garnishing. If you like the idea of growing your herbs, you can grow dill plants or even mint.
4. Azalea
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Azaleas, or flowering shrubs, produce beautiful blooms and fill entire bushes. They are easy to grow, making them ideal for cultivation under trees. These are usually slow growers, but once they bloom their large, leathery leaves will need regular trimming. However, you have a problem.
“Surprisingly, everyone’s favorite vibrant azaleas and rhododendrons that bloom all fall can cause serious illnesses in dogs, cats, and horses, including acute indigestion,” says Whitney. “They have also historically been used in chemical warfare and can cause severe respiratory problems, paralysis, coma and death if ingested by humans.”
Instead try: Several other flowering shrubs provide lush and fragrant foliage. Rhododendrons are aesthetic, can be large-leaved or small-leaved, consist of flowering shrubs of different sizes. Hydrangeas can grow up to 22 feet tall and develop into attractive bouquet-like formations, plus they are easy to care for, especially when pruned and placed in vases.
Viburnum is also a popular flowering shrub that may not produce as profuse blooms as azaleas, hydrangeas or rhododendrons, but will still add splendor to gardens.
5. English ivy
(Image credit: English Ivy)
English ivy is the most well-known plant, and while it looks great in a garden, it can quickly become invasive and dangerous. It can quickly spread throughout the garden and kill your other plants. It can also pose health risks as it is somewhat toxic and can cause itchy skin or dermatitis.
“English ivy is widespread throughout Europe and dangerous for your home,” says Bradley. “With a strong wall-climbing ability, this garden invader could easily enter your wall cracks, damaging the mortar and bringing moisture or leaks into the home.”
“English Ivy can be removed with bare hands by gently peeling it off the wall,” says Bradley. “You can also kill them by cutting off their roots and letting them dry out. However, not all wall climbing plants are harmful, e.g. B. Boston Ivy, so we recommend consulting a professional before accidentally pruning some beautiful and safe plants from your wall.
Instead try: Because English ivy is essentially a creeper, you might look at other creepers or vines as substitutes, such as English ivy. For these creepers to really shine, make sure you grow them on your garden fence or on your outside walls for a decorative touch.
6. Giant Bear Claw
Giant Hogweed or Heracleum mantegazzianum can be biennial or perennial. It produces white flowers in umbels, all pointing upwards. The flower heads can grow up to 60 cm. The plant contains high levels of furanocoumarins, a chemical that causes a burning sensation on the skin.
“Keep an eye out for giant hogweed, an invasive species that resembles cow parsley and can grow up to 16 feet tall,” says Jo Lambell of Beards & Daisies. “Its juice can cause burns, so if you come across it, wear gloves and protect your skin when removing it.”
Try instead: If you want to start a flower garden, look for healthier, sustainable alternatives. “A lovely substitute with similar lacy white flowers and tall billowing stems is Ammi Majus (False Bishop’s Herb) or for an injection of lime yellow color with a similar star-shaped flowerhead try Anethum graveolens,” say Annie & Jemma.
7. Arum Lily
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This is an evergreen plant typically found in subtropical climates that experience year-round rainfall and relatively mild winters. The leaves are 14 to 16 inches long, shiny and green. The flowers, mostly in white, pink, yellow or purple tones, are not only popular indoor plants, but also long-lasting as cut flowers.
“Zantedeschia aethiopica (arum lily) is often found in shady, moist areas and is admired for its showy trumpet-shaped flowers,” say Annie and Jemma. “They are considered invasive due to the speed at which they set seeds and can cause natural waterways to become clogged. The berries are poisonous if eaten and the leaves are irritating to the touch.’
Instead try: “A very similar alternative is the close relative; Calla Lily,” say Annie and Jemma. “Although still a plant you don’t want to eat, they have similar trumpet-shaped flowers, are non-invasive and come in a wide variety of colors.”