Arizona weeds with sticky seeds

Seeds That Stick To Clothing: Different Types Of Hitchhiker Plants

Even now, they’re lingering along the roadside waiting for you to pick them up and take them wherever you’re going. Some will ride inside your car, others on the chassis and a few lucky ones will find their way into your clothing. Yes, weeds that spread by people, or hitchhiking, have certainly taken advantage of you this year. In fact, the average car carries two to four seeds for hitchhiker plants at any given time!

What are Hitchhiker Weeds?

Weed seeds spread in a variety of ways, whether traveling by water, by air, or on animals. The group of weeds nicknamed the “hitchhikers” are seeds that stick to clothing and fur, making it difficult to dislodge them immediately. Their variously barbed adaptations ensure that the seeds will travel far and wide via animal locomotion, and most can be eventually shaken off down the road somewhere.

Although it might sound like all fun and games, the weeds spread by people are not only difficult to contain, they’re costly for everyone. Farmers lose an estimated $7.4 billion each year in productivity to eradicate these pest plants. Humans are spreading these seeds at a rate of 500 million to one billion seeds a year in cars alone!

Although the weeds within crop stands are annoying, those that appear in fields can be downright dangerous for grazing animals like horses and cattle.

Types of Hitchhiker Plants

There are at least 600 weed species that travel by hitchhiking with humans or on machines, 248 of which are considered noxious or invasive plants in North America. They come from every kind of plant, from herbaceous annuals to woody shrubs, and occupy every corner of the world. A few plants you might be familiar with include the following:

  • “Stick-tight” Harpagonella (Harpagonella palmeri)
  • “Beggerticks” (Bidens) (Krameria grayi) (Tribulus terrestris) (Opuntia bigelovii) (Torilis arvensis) (Symphyotrichum lateriflorum) (Arctium minus) (Cynoglossum officinale) (Cenchrus)

You can help slow the spread of these hitchhikers by carefully inspecting your clothing and pets before emerging from a wild area full of seeding plants, making sure to leave those unwanted weeds behind. Also, reseeding disturbed areas like your garden plot with a cover crop can ensure that there’s too much competition for hitchhikers to thrive.

Once those weeds emerge, digging them out is the only cure. Make sure to get three to four inches (7.5 to 10 cm.) of root when the plant is young, or else it’ll grow back from root fragments. If your problem plant is already flowering or going to seed, you can clip it at the ground and carefully bag it for disposal – composting will not destroy many of these types of weeds.

Last, but not least, check your car any time you’ve been driving on unpaved roads or through muddy areas. Even if you don’t see any weed seeds, it wouldn’t hurt to clean your wheel wells, undercarriage and any other location where seeds might be hitching a ride.

Verdolagas or Purslane

Verdolagas, as they are called among Latinx communities, goes by many names including purslane, wild portulaca, little hogweed, and others. This plant is very prolific during the monsoon season. It also can make an appearance in the spring if there are adequate spring rains. An introduced species from Europe, they have naturalized throughout the Southwest.

Common Purslane (Portulaca oleracea) on the left and Horse Purslane (Trianthena portulacastrum) on the right along with Bermuda grass.

Common Purslane or simply Purslane (Portulaca oleracea) is the most desired type. Common purslane should not be confused with another similar plant called Horse Purslane (Trianthema portulacastrum) which, while edible, is much less palatable and may irritate the throat. These two often grow side by side in places where the earth has been disturbed. The leaf shape is quite distinctive between the two as well as the flower color. Common purslane has elongated leaves broadest at the tip, similar to a boat oar, and yellow flowers. Variation exists and leave size is larger with more watered plants and some have a small notch in the tip of the leaf. Horse purslane has larger, rounded leaves more similar to coins. The leaves tend to be thicker and waxier and the flowers are pinkish-purple, never yellow. Both have green leaves with slightly reddish edges, the amount of red varies by plant and intensifies with water stress.

Verdolagas can be eaten much like spinach. Raw in salads, stir fried, in soups, or even pickled are common preparations. Purslane’s nearly global presence has resulting in many inventive recipes and uses. It has a pleasant slightly sour and salty taste. My one year old son is definitely a salty taste lover and can’t get enough. Although he might just love the idea of eating things he picks in the yard himself. Purslane is extremely high in omega-3 fatty acids, particularly alpha-linolenic acid.

Purslane grows low to the ground and while they can be large they are not particularly threatening to the growth of other plants. In fact they can be considered beneficial companion plants. Their roots travel deep and can help provide pathways for roots of other plants that cannot penetrate deep on their own in harder soils. The deep roots bring up moisture and their ground covering avility creates a humid microclimate for nearby plants.

Because purslane can be eaten and it is beneficial for other plants it is encouraged that you keep it growing. If you are not lucky enough to have Purslane grow wild near you, Native Seeds/SEARCH offers Golden Purslane , a cultivated variety that is great for eating. It is also possible to harvest some desired plants from one area and spread around where you want the plants to appear. They produce abundant seeds over their life-span. When you harvest the plants for eating, wash in a bowl and deposit the water where you want the plants to appear. The rinse water will most certainly have seeds that washed out from the cone shaped seed pods. The seeds can also be collected and stored from drying plants.

Puncture Vine

The yellow-flowered common purslane is not to be confused with the similar looking Tribulus terrestris, aka puncturevine or goathead. Puncturevine has a similar low growing ground cover habitat in disturbed soils and elongated leaves like purslane but is much less desirable because the long burs on the fruits. Puncturevine does not have the succulent-like leaf characteristics. The burs develop just a few days after flowering so if you see the plants flowering pull immediately or risk getting a bur puncturing through your sandal or bike tire. The burs are the seed pods so be careful where you discard to avoid an encounter next season. The seed lie dormant for long periods of time and are erupted with the increase in moisture of the monsoon. Visit here for identification help.


This is probably one of the most ubiquitous wild plants throughout the Southwest and beyond. Amaranthus palmeri¸ aka pigweed, Palmer’s amaranth, and careless weed, produces copious amounts of seeds that can live in the soil for decades resulting is a seemingly never ending supply. It grows extremely fast, can reach up to 8 feet high and has deep root systems. This makes it a particularly difficult foe for larger scale farmers because the vigorous growth chokes out low growing crops like beans and cotton. Unfortunately it’s ability to take up nitrogen results in it being poorly suited to most livestock because of the high nitrates. This is another reason humans shouldn’t consume in high amounts or harvest from areas which receive an excess of nitrogen fertilizer.

But on a small scale like your backyard garden, amaranth can be a welcomed addition to your garden. The leaves are usually green but can also have red veins and undersides. They can be smooth rounded leaves or serrated. There is a lot of variability in wild amaranths but once you are familiar it is easy to identify. The leaves are very similar to domesticated varieties but the flower is quite different. Domesticated varieties were selected for their grain as well as the greens so the grain or seed producing flowers tend to be larger and denser.

Wild Palmer’s amaranth on the far left. Domesticated Amaranthus cruentus varieties on the right. Domesticated varieties are Mountain Pima Greens and Hopi Red Dye.

Amaranth greens are highly nutritious and high in vitamins. They are particularly high in protein, iron, calcium, and folic acid. They are best eaten when the leaves are young, just under 2-3 inches long. I think the stage in the picture below is perfect for raw salads. Larger leaves are best cooked. The wild varieties commonly found tend to have very prickly leaves and stems as they grow larger. Drought and full sun make them even tougher and unpleasant in texture, almost woody. Domesticated varieties have a more pleasing texture at all sizes.

Seeds from wild amaranth can also be eaten. Although they are small and black witch differs from commercially available amaranth grain and flour which is golden in color. To harvest the seeds shake mature flowers into a paper bag and winnow away flower bracts. Wild amaranths have prickly steams that can make harvesting the grain a nuisance compared to domesticated varieties. The seeds can be added into baked goods, cereal, and granola. Recipes for amaranth greens and grain can be found elsewhere on our website .

Amaranth is a big pollen producer which gives it an advantage in producing seeds but also can be very irritating to allergen suffers. Removing before it flowers eliminates pollen production.

Young amaranth sprouts resulting from recent monsoon rains in Tucson. Photo courtesy of Charlotte Handy.


Now this is an interesting plant that when it appears often has people wondering if they planted watermelon as the leaves are similar between the two very different species. Once it flowers it becomes even more confusing because it’s flower resemble tomatoes and other nightshade cousins. Buffalobur (Solanum rostratum) definitely falls within the undesired weed category. If the stinging spines weren’t bad enough it is extremely poisonous. According to NS/S Conservation Program Manager, Nicholas Garber, “Every part of the plant is poisonous and the stinging spines can cause long-lasting pain.. The plant accumulates so much nitrogen from the soil that the level of nitrates in the plant would be poisonous on their own even without all the poisonous alkaloids!”

Botany enthusiasts might be the only type of person to see some beauty in this plant. Their flowers are hereranthery, which means the flower has stamens of different sizes (four straight, yellow anthers are the same size, and one is longer, brown and curved). Heteranthery is very complicated in an evolutionary framework and believed to allow for some of the pollen to be food for pollinators while allowing the rest for sexual reproduction. It’s a good idea to kill this plant on-sight (at least until it becomes endangered), using tools because the spines can pierce leather gloves. It is not a widespread plant but common in urban areas and farm and grazing lands because it likes disturbed soils. The burs or seed pods can be carried long distances from the source plant on hiking boots and in animal fur.

Buffalo Bur growing at the Native Seeds/SEARCH Conservation Center in Tucson.

There are numerous other wild plants that might be making an appearance in your garden this monsoon season. Some are potentially poisonous like jimsonweed (Datura wrightii) while others are desirable edible wild plants like Desert Ruhbarb (Rumex hymenosepalus) . Others, like the many different varieties of devil’s claw(Proboscidea spp.) , can be both edible and a nuisance if your unlucky and get a tangle of dried pods wrapped around your ankle. Whatever unknown plants start popping up in your garden after the soaking rains consider identifying before pulling to determine if it is truly unwanted or undesirable. You may just find that you have been given an edible gift.

Arizona weeds with sticky seeds

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