6. Lily of the Valley
Like foxglove, lily of the valley is graded Class 1 on the poison scale, meaning it can kill. The delicate white flowers look sweetly innocent and bely the fact that lily of the valley is one of the most dangerous plants. Ingesting just a tiny amount of any part of this plant can kill you, your kids, or your pets. Like foxglove, lily of the valley contains super-high concentrations of cardiac glycosides, which is how it kills if ingested. It's also a severe irritant to the skin, so you should never handle it without gloves.
7. Monkshood
Monkshood, also known as wolfsbane, features deep blue-purple hooded flowers, but it's lethal to humans and pets. Even handling this plant without gloves can cause severe symptoms and potentially kill you. Monkshood contains a variety of toxic substances, including neurotoxins and cardiopulmonary toxins. The most deadly is aconitine, which causes cardiopulmonary collapse and is a potent nerve agent. All parts of this plant, including the sap, are potentially lethal if eaten, and it only takes a tiny amount to kill.
8. Poison Ivy
Poison ivy is an all-too-common native plant that causes itchy, painful skin irritation. If you’ve heard the old saying, "leaves of three, let it be," it applies to poison ivy because each leaf consists of three leaflets which appear to be individual leaves growing in a cluster of three. There are several poison ivy species, some growing as a low shrub and others as a climbing vine.
Poison ivy, like poison oak and sumac, contains urushiol oil, which acts as a (sometimes extreme) skin irritant that can cause anything from mildly itchy contact dermatitis to large, extremely painful blisters and, in rare cases, anaphylaxis.
9. Poison Oak
Poison oak is a leafy shrub that can reach heights of 6 feet and has leaves most commonly in threes, although some plants produce foliage with clusters of up to nine leaflets. This is another plant that contains urushiol oil and causes the same type of itchy, painful topical irritation as poison ivy.
If exposed, you’ll notice redness and itching within 48 hours of exposure. Next comes bumps that eventually morph into large blisters. They’ll slowly heal and chances are you’ll be back to normal in 2 to 4 weeks.
Note that while poison oak and poison ivy are both dangerous plants that you want to get rid of, handle them with extreme caution and never burn them. Burning these plants spreads the oils in the smoke from the fire, and this can cause serious respiratory conditions that need immediate medical treatment.
10. Stinging Nettles
Stinging nettles are one of the most common poisonous plants in the world. And while only really a minor irritant with many traditional herbal benefits, these hairy little plants hurt. Delicate dog paws and the sensitive skin of rambunctious kiddos are the most at risk from pain from stinging nettles. The hairs on the leaves and stems of the plant are hollow and when they touch your skin, chemicals flow down the hollow "hairs" into your skin, causing stinging and itching.
Most people experience a temporary stinging and itching sensation and may have a red, bumpy rash. In very rare cases, highly allergic people can go into anaphylactic shock and need immediate medical assistance. Even if you're not dangerously allergic, nettle rash is incredibly unpleasant, but you need to do more than just pull up the leafy parts. Nettles spread vigorously via rhizomes (a system of underground tubers and roots), You need to dig up these rhizomes to get rid of the nettles, as many are tough enough to withstand weed killer.
If you have any doubt about the safety of the weeds or plants on your property, call a garden design pro to identify and remove potentially dangerous plants. They can also help you choose ones that beautify your outdoor space safely and even find pet-friendly plants to keep pests away.