8 Dangerous Plants to Avoid Growing in the Garden
Here at J&R Pierce Family Farm, I think it’s important to connect my readers with valuable insight from other experts. Today’s post is a guest post brought to you by Samantha Rainwater.
While most plants will look absolutely wonderful growing in your garden, there are a few that should be avoided for their potentially devastating toxicity.
While most commonly grown plants pose no threat to humans, pets, or wildlife, there are some that can be dangerous to keep around. Many seemingly harmless flowers contain toxins that can be dangerous to people—particularly children—and pets. If you have young children or curious animals, it is usually best to avoid these potentially dangerous plants altogether.
Many gardeners are surprised to find that some of their favorite flowers are toxic, making them potentially dangerous to have around. In some cases, you can still safely grow these plants, particularly if you have no young kids, outdoor pets, or curious neighbor kids, or you place fencing around these plants as a precautionary measure.
Otherwise, you may be better off safe than sorry when it comes to the following potentially dangerous plants.
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What Are the Top 10 Most Dangerous Plants?
In this post, I’ll tell you about the most common dangerous garden plants - but for curiosity’s sake, here are 10 of the most dangerous plants in the world:
Nerium oleander
Rosary pea
Deadly nightshade
Castor oil plant
English yew
Machineel
White snakeroot
Aconite
Water hemlock
Want to learn more? Be sure to check out this deadly plant video:
8 Dangerous Plants to Avoid Growing in the Garden
Foxglove
Foxgloves are unique-looking plants that bring large stalks of beautiful flowers in pink, purple, white, yellow, and red. When in bloom, these flowers are a cone shape, approximately the size of a fox’s paw—hence the name ‘foxglove’. These plants are considered hardy perennials in growing zones four through ten and can be grown in both full-sun and partial-sun locations.
All parts of the foxglove plant contain poisonous substances including the flowers, leaves, stems, and the seeds. One of the toxic substances found in foxglove plants—digitalis glycoside—is used in certain heart medications but can be very dangerous in the wrong quantities and should never be taken without a doctor’s prescription—it should also only be taken through approved channels, not via a plant growing in your yard.
Symptoms of ingesting any part of a foxglove plant may include slowed or irregular heartbeat, low blood pressure, blurred vision, confusion, disorientation, hallucinations, headache, lethargy, stomach pain, vomiting, nausea, diarrhea, and weakness. If you or someone in your care has eaten any part of a foxglove, it is important to seek medical care immediately.
Alternatives:
Mountain Hollyhock
Hydrangea
Hydrangeas are a wildly popular shrub that bloom large clusters of flowers in blue, pink, green, purple, red, and white colors.
These shrubs have a fairly large growing zone range and grow as hardy perennials in zones three through nine. Hydrangeas are also fairly versatile and can grow anywhere from full-sun to shady locations as long as they are provided with enough nutrients from the soil. While these flowers are a popular choice among many landscapers, they do pose a potential threat to curious pets.
Hydrangea shrubs contain a toxic substance called cyanogenic glycoside which, if ingested, can lead to vomiting, diarrhea, depression, and other gastrointestinal problems.
Many cyanogenic glycoside poisonings are mislabeled as other gastrointestinal issues when it is not clear that a hydrangea plant was consumed—these poisonings are most common in pets. If your cat, dog, chickens, or other animal consumes too much of any part of the hydrangea plant, it is important to take them to your local vet if they start to show symptoms.
Alternatives:
Spirea
Peony
Holly
Hollies are evergreen shrubs—sometimes grown as trees—that are often used in landscaping or as privacy barriers due to their dense foliage.
These plants are hardy in growing zones five through nine, and they can reach heights of up to 50 feet and spread up to 40 feet wide, giving them a large footprint at maturity if allowed to grow freely. The female holly plants grow small, round, and brightly colored red berries, which may look pretty but contain a substance that is poisonous to both humans and animals.
The berries that grow on some holly plants contain toxic substances called saponins which, when ingested, can cause vomiting, diarrhea, and depression in animals and people. These bright red berries can be enticing to young children, so it is important to make sure they understand that they are not edible. Holly plants are also often used as decorations during the holidays.
If there are berries on the plants when they’re brought inside, they will dry out and may fall off over time.
Dried berries that drop to the floor are easily consumed by young children and animals, so you may want to consider removing the berries before adding them as an indoor decoration. While holly berry poisonings are not usually severe, if enough is consumed, it may be a good idea to contact your local medical office or vet’s office to seek advice.
Alternatives:
Blueberries
Yaupon holly
Morning Glory
Morning glories are popular landscaping flowers that are grown in a wide range of climates. Although most morning glories will only grow as perennials in growing zones eight and nine, they are often grown as annuals in growing zones three through seven and in zone ten. In many of these regions, morning glories will reseed themselves, starting new flowers for the following year.
So although they may not be true perennials in zones three through seven and zone ten, they can still appear as perennials with no effort from the grower. Morning glories can be found in pink, purple, blue, red, and white and are known for attracting birds, butterflies, and other pollinators.
When it comes to being dangerous, the morning glory appears to be relatively safe to have around. However, while the flowers, leaves, and stems pose no threat, the seeds do contain a poisonous chemical that has a similar structure and property to the drug LSD.
The indole alkaloids found in the seeds are what are responsible for the poisonous traits. As previously mentioned, the morning glory is good at reseeding itself, meaning it will drop its seeds in the nearby vicinity, making them easily accessible to wandering animals. Although it is more unlikely that children will get into the seeds, it is best to take caution when morning glories are around.
The most common symptoms of ingesting morning glory seeds are vomiting, diarrhea, and other intestinal ailments. If a large quantity of the seeds are consumed, hallucinations may also occur.
Alternatives:
Azalea
Azaleas are a popular flowering shrub that are a member of the rhododendron family. These shrubs are best known for their high flower yield, bright colors, and minimal requirements to thrive in nearly any condition.
Most varieties of the azalea shrub grow best in growing zones six through nine, although there are some varieties that do well in zones four through nine. While pink seems to be one of the most popular color varieties for azaleas, they can also be found in red, purple, orange, yellow, and white. While the azalea shrub may sound like an attractive option for your landscaping, you may want to think twice if you have young kids or curious animals at home.
Every part of the azalea shrub is toxic to both humans and most animals—including cats, dogs, horses, and livestock. The poisonous substance found in azalea shrubs is called grayanotoxin—more commonly referred to as ‘mad honey’—which can be found in any member of the rhododendron family.
In humans, symptoms of ingesting any part of the azalea shrub may include vomiting, lowered heart rate, low blood pressure, irregular heart rhythm, convulsions, blurred vision, mild paralysis, tingling, seizures, and hallucinations. In animals, symptoms may include blindness, irregular heart rhythm, abdominal pain, depression, excessive drooling, vomiting, difficulty walking, tremors, seizures, loss of appetite, and comas. These symptoms can all be very serious and require immediate medical attention from a healthcare professional or veterinary doctor.
Alternatives:
Dogwood
Vinca
There are several varieties of vinca flowers which are commonly referred to as periwinkle. Many varieties are tropical and will only grow as perennials in tropical growing zones; in most growing regions, they are grown as annual flowers.
Some varieties have been bred to grow as perennials in growing zones seven through nine, although they are still most commonly grown as annuals. The periwinkle blue color is the most classic color that vincas are found in, although they also come in purple and white colors.
Although vinca flowers look beautiful in hanging baskets, potted on the porch, and even planted in the ground, there are some risks involved in keeping these plants around.
There are two substances found in vinca plants that are considered toxic to both humans and pets—vincristine and vinblastine.
While these substances generally don’t cause fatal reactions when consumed, they can cause diarrhea, vomiting, loss of coordination, seizures, and depression in animals. In humans, symptoms can range from abdominal cramping and discomfort to heart complications if too much is consumed. Low blood pressure—or hypotension—is also common when the plant is consumed. Both vincristine and vinblastine are used in chemotherapy, and they are also used in some blood pressure control medication.
While they can be safely consumed when given by a doctor in controlled medications, ingesting plants containing these substances can result in overdosing, leading to the unpleasant and potentially dangerous side effects mentioned previously.
Alternatives:
Hollyhock
Wisteria
The wisteria plant is a beautiful flowering vine that is popular among many landscapers due to its long bunches of cascading flowers which are found in blue, purple, and white. Wisteria vines are aggressive growers and will quickly fill an area—this can be good or bad depending on your landscaping goals.
Some species of wisteria are considered invasive, although there are a few native varieties that are more preferable to grow in the United States. Most varieties of wisteria grow as perennials in growing zones four through nine, although they require a decent amount of pruning each year to stay healthy enough to continue blooming season after season.
While wisteria is a beautiful choice for many landscape settings, the seeds and seed pods do pose a potential threat to children and animals. Both the seeds and the pods contain the chemical lectin and wisterin glycoside, both of which have toxic properties. Thankfully, since these chemicals are only found in the seeds and their pods, it is uncommon for much poison to be consumed.
Since such small amounts of these harmful chemicals are generally consumed at once, symptoms in humans are generally limited to a burning sensation in the mouth, vomiting, diarrhea, and stomach pain. In animals, symptoms may include vomiting (with or without blood), diarrhea, and depression.
Alternatives:
Magnifica honeysuckle
Daphne
There are a wide variety of daphne plants that we can grow, but the most popular varieties are the odora, mezereum, and transatlantica varieties. All of these daphne plants are flowering shrubs that most commonly bloom in pink and white color variations. These shrubs also produce berries which begin to form after the flowers have finished blooming for the season.
The berries continue to add color to your garden long after the flowers have been spent, making
these shrubs a popular choice. In many climates, the leaves are evergreen, meaning they will keep their color all year long.
Most varieties of daphne grow as perennials in growing zones four through nine, but they are slow to mature. Although the yearly color of the daphne shrub sounds appealing, they also house a highly poisonous substance and should be avoided when children and pets live nearby.
All varieties of daphne are considered toxic to humans and animals, but the odora variety is particularly toxic and is therefore best to avoid. This variety of daphne is considered highly poisonous and can cause skin damage and rash from simply touching any part of the plant.
Consuming the plant is even more dangerous and can result in blistering in the mouth, throat, and stomach. Symptoms include vomiting, bloody diarrhea, and drooling (primarily in animals). In severe cases, seizures, comas, and death have occurred, although these are not as common.
Thankfully most parts of the plant have a strong bitter taste which deters humans and animals from consuming large amounts.
Alternatives:
Virginia spiderwort
What To Do if a Toxic Plant is Ingested
If you suspect that your pet or a child has consumed any part of a toxic plant, the most appropriate action is to contact a healthcare professional (or veterinarian if it’s an animal) and ask for their advice on how to best proceed.
While many toxic plants are not life-threatening, the symptoms can be uncomfortable and even painful.
Consequently, a doctor may be able to speed along the negative side effects. If a serious reaction to ingesting any plant is noticed, it may be best to take the child or animal to a healthcare professional right away. In some cases it may be safest to get the ingested plant out of the individual’s system, although this should never be done at home unless instructed to do so by a healthcare professional.
A poison hotline is also an appropriate number to call if your doctor is not immediately available.
Have you ever grown one of these plants in your garden - and safely? Let us know if you have any other tips to keep in mind - and be sure to check out this garden planning chart so you always know exactly what to plant.
Samantha Rainwater is a full-time business owner and recent mom who spends her free time writing. Her degree in Biology gives her a background in science, which she likes to apply on her small hobby farm. Writing about her experiences is one of her passions, and she finds joy in sharing her experiences with others.
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