11 Dangerous Plants That Could Threaten Your Garden this Halloween

You may not realise that some of the most common garden plants are actually dangerous flowers to cats and dogs. Pets can be curious around plants and may nibble leaves, flowers, or berries, leading to vomiting, diarrhoea, heart problems, or even worse.

What flowers are poisonous to cats?

So, are flowers poisonous to cats? Unfortunately, yes, some are. For example, Lilies of all variants are highly poisonous to cats, which is why we offer lily-free bouquets. If your cat eats or licks a lily, it can cause kidney failure, even with minimal exposure. Other poisonous flowers like foxgloves and monkshood plants can also be fatal to cats.

But what if you’re looking for safe options? Thankfully, there are non-poisonous flowers for cats such as roses, gerberas, and freesia that can safely brighten your home. If you’re looking for greenery, house plants that are not toxic to cats include spider plants, areca palms, and Boston ferns.

What flowers are poisonous to dogs?

People also ask us ‘What flowers are poisonous to dogs?’ Well, sadly for man’s best friend there are some dangerous flowers for our dogs. Some of the biggest culprits include yew trees, autumn crocus plants, and laburnum pods, all of which cause vomiting, weakness and potentially even collapse in dogs. Furthermore, ivy berries can irritate your pooch’s stomach and skin. 

However, safer alternatives do exist, so  we recommend checking before buying bouquets for yourselves or any loved ones with furry friends. There are flowers that are not poisonous to dogs, such as snapdragons, orchids, and marigolds. Choosing these flowers allows you to enjoy your floral displays without putting your pets at risk.

1. Deadly Nightshade (Belladonna)

The deadly nightshade flower (also known as Belladonna) is one of the most poisonous flowers in the UK. Its glossy black berries can look deceptively sweet, but they can cause hallucinations, seizures, and even death due to its ingredients. These can affect your nervous system by disrupting signals between your nerves and muscles.

Nightshade typically flowers from June to September, and its berries can easily be mistaken for elderberries or blackcurrants (both harmless when prepared properly), which increases the risk of accidental ingestion. 

For the Halloween lovers, historically, deadly nightshade was even used in ‘witches’ potions due to its hallucinogenic effects, but be sure to stay clear of it if you spot it in the wild.

2. Foxglove

The foxglove plant is noticeable for its tall spires of purple, pink, or white blooms, but it hides powerful toxins (digitalis glycosides) that can affect your heart’s rhythm and be fatal if consumed.

Foxglove poisoning symptoms include nausea, vomiting, stomach pain, and dizziness, which can develop into more serious effects such as irregular heartbeat and confusion.

Foxgloves bloom from June to September, but their seed pods remain throughout October, which means you need to be extra vigilant on autumn walks. Do not confuse foxgloves with comfrey, which are also tall and leafy but have smaller, clustered flowers. 

If you find foxgloves growing in your garden and want to remove them, take extreme care. Always wear thick gloves, as even handling the plant can irritate the skin. Dig carefully around the base to pull up the roots in full, otherwise the plant is likely to regrow the following season. Dispose of the plant material safely, and never add foxgloves to compost heaps where pets or wildlife could come into contact with them.

3. Monkshood (Wolfsbane)

A plant famously believed to repel werewolves and vampires, the Monkshood plant, also called wolfsbane, produces hooded blue-purple flowers and is one of the most highly toxic plants in Europe. Its toxin (aconitine) is so powerful that it can cause irregular heartbeat and paralysis from minimal skin contact alone.

Monkswood usually flowers from late summer throughout October, and is often mistaken for delphiniums, which share a similar tall shape and rich blue flowers. While delphiniums are also toxic, monkshood is far more dangerous and should never be handled without extreme care.

If you find monkshood in your garden, wear thick gloves, long sleeves, and dig out the roots to stop regrowth. However, removal is best left to professionals.

4. Yew Tree

Tied to graveyards for centuries because of its association with death, every part of the yew tree is toxic to humans. Though its bright red berries often draw attention, and the berry is technically harmless, the seeds inside the berry are highly toxic, and even a small amount can be fatal if eaten. 

Yew berries can sometimes be confused with guelder-rose or hawthorn berries, both of which are safe for wildlife and humans in moderation. Unlike these, a yew tree has needle-like evergreen leaves.

Because of its toxicity, the yew tree should never be planted in gardens where children or pets roam freely, and in the wild, fallen clippings can be especially dangerous to grazing animals like horses and cattle.

5. Lords-and-Ladies (arum maculatum)

The lords and ladies plant (also known as cuckoo-pint) produces arrow-shaped leaves in spring and spikes of bright red berries in autumn. The berries look enticing to children, but ingestion can cause your mouth and throat to swell, difficulty breathing, and upset your stomach

Many people may confuse lords-and-ladies with wild garlic, particularly when it first emerges in spring, due to their shared broad green leaves. To distinguish between them, crush the leaves; wild garlic will release a strong scent, whilst lords-and-ladies will not.

If you’re wondering how to get rid of lords and ladies plants, dig up the tubers carefully while wearing gloves, as the sap can irritate skin, and be persistent, as the tubers often regrow if left behind.

6. Poison Hemlock

Infamous for its role in the death of Socrates, the poison hemlock plant remains one of the most highly toxic plants in the UK. It produces tall hollow stems with umbrella-like clusters of small white flowers. If you ingest even a small amount, it can lead to muscle paralysis or respiratory failure. 

Hemlock looks strikingly similar to cow parsley and Queen Anne’s lace, but you can identify hemlock by its purple-spotted stems and an unpleasant, musty smell.

You may wonder what to do if you touch poison hemlock: wash the skin immediately, avoid touching your mouth or eyes, and seek medical help if hemlock plant poisoning symptoms occur. Because it spreads quickly in damp ground, hemlock is difficult to control. You should consult a professional if infestations have grown out of hand; otherwise, remove carefully with gloves.

7. Giant Hogweed

Perhaps the most notorious plant in Britain, giant hogweed can grow up to five metres with thick, blotched stems and huge umbrella-like flowers. The sap is extremely phototoxic, which means it reacts with sunlight and causes blistering and long-term scarring. Cases of burns from giant hogweed are reported every summer and autumn, making it one of the most invasive plants in the UK. 

You can easily confuse giant hogweed with common hogweed and cow parsley, but those plants are much smaller. A good rule of thumb is if it towers over you, treat it as dangerous.

Each year, many gardeners search for advice on how to get rid of giant hogweed, but this is best left to professionals. However, if you do attempt removal, wear protective clothing and never use a strimmer or mower as this can spread sap particles.

 8. Lily of the Valley

The delicate bell-shaped blooms of lily of the valley (Convallaria) hide potent toxins known as cardiac glycosides. Ingesting them can cause vomiting, confusion, and potentially fatal heart problems. Your pets are especially at risk, as even small amounts are dangerous.

Its spring shoots can be mistaken for wild garlic or even bluebells, both of which are safer. Again, the garlic test works, as the lily of the valley has no pungent scent.

Despite its dangers, it remains popular in ornamental gardens. If you do want to feature this plant in your garden, make sure to plant it away from areas accessible to children or pets.

 9. Laburnum

With its golden hanging chains of flowers, the laburnum tree is a popular ornamental feature in UK gardens. However, its seed pods are highly toxic and resemble peas, making them especially dangerous to children.

So, is laburnum poisonous? Yes, ingesting the pods can cause nausea, convulsions, and even comas.

While the flowers bloom in late spring, the pods remain into autumn, making them a Halloween hazard. Regularly prune fallen pods and avoid planting laburnum near play areas in your garden.

 10. Autumn Crocus

The autumn crocus plant will often appear in your garden around Halloween, with delicate lilac flowers; however, it isn’t one to ignore, as it contains colchicine, a toxin that can lead to kidney and liver failure if ingested.

The blooms are sometimes confused with spring crocuses, which are less toxic, or with wild garlic shoots in early growth stages. Again, unlike wild garlic, autumn crocus lacks the distinctive smell.

Because of its late flowering, autumn crocus is often overlooked in gardens, making awareness all the more important.

 11. Ivy

A classic climbing plant, ivy grows on walls, fences, and trees across the UK. While ornamental ivy varieties are usually safe, wild ivy produces berries that are poisonous to humans and animals. Ingesting them can cause vomiting, diarrhoea, and breathing difficulties. Contact with ivy sap can also irritate the skin.

Ivy berries can resemble elderberries or privet berries, both of which are also toxic but differ in leaf shape.

Many homeowners search for how to kill ivy as it spreads aggressively throughout our gardens. Cutting back to the base and digging out the roots is the most effective method to rid yourself of any ivy, although some persistence is required as the plant often regrows.