Pictures of poisonous plants can help you to identify vegetation, berries, etc. that shouldn't be eaten. But my list extends beyond this narrow definition of “toxicity” to include weeds that cause rashes on contact. As you browse my list and photos, you'll also find information about beneficial weeds: natural remedies that help counteract the itching caused by a couple of noxious weeds. My list and pictures are meant to be a springboard for further study; always consult with medical professionals when you suspect that you've wound up on the wrong end of an encounter with poison (in any form)!

David BeaulieuBittersweet nightshade is a very common weed and especially dangerous to have around kids, as they're attracted to its brightly colored berries. Yet relatively few parents would be able to identify bittersweet nightshade on their property. This article also contains information about the vines more widely recognized as "bittersweet" (but which are quite distinct from bittersweet nightshade). Related to bittersweet nightshade (and equally toxic) is a specimen commonly grown by crafts enthusiasts:
Chinese lanterns.

David BeaulieuFoxgloves grow well in
dry shade -- often a problematic area in the yard. But they are among the most toxic specimens commonly grown on the landscape. Do not grow them if small children will be spending time in the yard.

David BeaulieuIf you live in the country in eastern North America, you may have some mountain laurel growing in your backyard. Cultivars of mountain laurel are also sold at nurseries, including the beautiful 'Minuet' laurel shown in the picture. Like mountain laurel,
azaleas and rhododendrons belong to the heath family -- and are toxic. Don't let pets nibble on any of these shrubs.

David BeaulieuCastor bean is a tropical widely grown as an annual in northern climes, often as a potted plant for patios, decks or porches. The leaves, stalk and seed-heads are all attractive. The laxative, castor oil is derived from castor bean plants, but so is the deadly toxin, ricin.

David BeaulieuYew bushes can be grown in sun or shade. Their shade-tolerance gives landscape designers an important option in challenging areas. But those fleshy, bright red berries contain a seed that's toxic.

David BeaulieuThe entries listed so far are all toxic if
eaten. But in the case of some other weeds, all you have to do is
touch them to be exposed to their toxicity -- and come down with a rash.
Poison sumac and poison ivy are examples. The former gives all sumac shrubs a bad name, despite the fact that most are quite harmless.

David Beaulieu What makes poison ivy toxic? It's an oil called, "urushiol." Urushiol's rash-inducing property has inspired a song, a DC Comics villain, and...well, much trepidation in people walking in the woods!
How can nature be so unfair as to hold this menace over our heads when we're simply trying to enjoy the great outdoors? Well, as if to balance things out, nature has also given us jewelweed.
Jewelweed is also called, "touch-me-not"; but not because it's toxic. Rather, jewelweed is considered a natural remedy for poison ivy rash. Like poison ivy, jewelweed is very common: both could very well be growing in your backyard. It's easy to identify jewelweed, once you recognize its flower: it's cornucopia-shaped, with a distinct little "tail."
It is more difficult to identify poison ivy, because there's no pretty flower to help you out (just a dull, insignificant bloom).

David Beaulieu "Easter" lilies is a misnomer for these toxic trumpets. You can thank the workers at a greenhouse somewhere for your being able to inhale their heady perfume at Easter in cold climates. The workers had to take great pains to trick them into blooming at what is -- truth be told -- really out of season for them.
Thus many Easter lily recipients in the North who decide to take a crack at growing them outside are disappointed when next spring rolls around and nary a flower is to be found on them. The fact is, you cannot expect Easter lilies to bloom outdoors for you much earlier than whatever other lilies you may be growing.
Would that this were our greatest concern in growing Lilium longiflorum, though. They are deadly toxic to cats!

David BeaulieuLike poison sumac and poison ivy, stinging nettles, as its name suggests, is not a plant you want to brush up against when working out in the yard. Your skin will burn with a painful itch for a short time after contact with its rash-inducing spines. Don't confuse stinging nettles with
dead nettles, a perennial used as a groundcover in shady areas.

David BeaulieuThe ASPCA lists yellow dock as being toxic to dogs. Like jewelweed, however, yellow dock (or "curly dock") is a medicinal plant that can be used to counteract the discomfort caused by one of the toxic entries included on this page. Just as jewelweed alleviates the itch caused by poison ivy rash, curly dock can soothe skin inflamed by stinging nettles. Just roll one of the fresh, green leaves of curly dock between thumb and forefinger, to crush it into a juicy pulp; then rub it on your burning skin. The picture shows the mature flower-head of a yellow dock plant, after its blooms have dried and assumed a coffee color.

David BeaulieuLantana bears colorful flower clusters (orange is a popular color, as in the picture) and is commonly used (as an annual) by gardeners in cold climates as a hanging plant. Growers in warmer climes are familiar with lantana as a shrub, where this vigorous grower may even be invasive. But its invasiveness is not the only caveat that comes with growing lantana: one part of this plant "may be fatal if eaten," according to the North Carolina Cooperative Extension....

David BeaulieuLily-of-the-valley is a traditional wedding flower. And why not? Its flowers are bell-shaped (think "wedding bells"), fragrant and white (think "innocence"). From the landscaping perspective, though, we might not want to push that innocence thing too far: lily-of-the-valley is invasive. And if you have children playing in the yard, it poses another problem: it is a poisonous plant. So you might want to study the picture (left) and make sure that this common ground cover is not growing in your yard (unless fragrance trumps toxicity and invasiveness for you).