Greenbelt Plant Guide

Click on the drop down menu below to learn more about each plant!

Black Cottonwood

The black cottonwood (Populus trichocarpa) is one of the fastest growing trees in North America, gaining 5’-8’ per year within its first 10 years of life, and trees may reach diameters of 6”-8” within that time! Black cottonwoods are a type of poplar tree that grows in moist soils, often found alongside willow and birch trees along the Greenbelt. Black cottonwoods are an important asset to the Greenbelt, as the trees help hold the banks of the Boise River together and provide critical shade for fish and other wildlife. These large native trees are a beaver favorite, which is why you’re likely to spot many with wire cages around their trunks. Barber Park is home to one of the largest and oldest black cottonwood forests in the region.
Find a knobby cottonwood stick (make sure its dry) and snap it in half. Can you find the star inside?
Learn more about the black cottonwood here.

Maples

Large maple trees (Sapindaceae sp.)are not native to Idaho but are found all along the Greenbelt. These trees can live up to 130 years and create shaded habitats used by wildlife and humans alike.
Maples, especially the boxelder, are the preferred habitat for the boxelder bug. These bugs are harmless but are known as a nuisance when they fly aimlessly into people enjoying the Greenbelt. As true bugs, their mouthparts are like a straw, made for piercing and sucking sap from leaves (they can’t bite you). Young boxelder bugs are bright red while the adults have black wings that grow over their backs.

Willow

The Pacific willow (Salix lucida) and yellow willow (Salix lutea) are two similar trees that are found everywhere along the Greenbelt. Just like other large trees along the Boise River, willows are important for keeping soil from washing away. Look for the willow’s red stringy roots along the edges of the river and under the water. Aphids, a type of insect, love eating the sap of willow trees. If you’re traveling along the Greenbelt on a sunny day and feel “rain drops,” its likely honeydew! Honeydew is the sweet sticky liquid produced by thousands of aphids in the leaves above your head!
Willow tree bark contains Salicin, a natural pain reliever that’s been used by indigenous peoples for thousands of years and is now the active ingredient in aspirin!
Learn more here.

Himalayan Blackberry

Despite the yummy berries that this blackberry species produces, the plant is invasive and shades out native plants under the thick canopy that these shrubs create. The Himalayan blackberry (Rubus armeniacus) has leaves that look similar to poison ivy, with its three leaflets and pointed tips, but the edges are serrated and the shrub itself has thorns. The shrub is part of the rose family, and produces fragrant white flowers in the early summer months.
The United States Department of Agriculture developed the marionberry in 1945 by crossing the Himalayan blackberry with a few other species of blackberry. Marionberries are the most widely cultivated blackberry and the one you’ll typically see at the market.

Showy Milkweed

Showy milkweed (Asclepias speciosa) is a native plant famous for benefitting monarch butterflies. Monarch butterflies use a nectar source and host plant for laying eggs. In fact, milkweeds are the only plants that monarchs will use for laying eggs. As such, milkweed is critical for the survival of monarchs. Without it, they can’t complete their life cycle. There are two types of milkweeds that are native to Idaho - the showy milkweed and the Mexican whorled milkweed (Asclepias fascicularis). Choose these species if you want to plant milkweed in your backyard to help monarch populations.
Monarchs will typically lay one egg per leaf to allow the caterpillar enough food to eat.
Learn more here.

Narrowleaf Plantain

Narrowleaf plantain (Plantago lanceolata) is an introduced species from Eurasia with medicinal properties. A tea from the leaves is used as a cough remedy and to improve infections in traditional medicine.
If you get an insect bite that “bugs” you, rub a plantain leaf on the irritated part of your skin to help ease the reaction.

False Indigo

False indigo (Amorpha fruticose) is native to the Midwest but grows in thick groves along the Greenbelt. Although false indigo produces stalks of pretty purple-navy flowers that provide food for pollinators, it is an invasive species that quickly overgrows native plants. The Boise River Enhancement Network has worked hard to remove false indigo and many other invasive species from the Greenbelt in order to make room for more beneficial native plants.

Rabbitbrush

Rabbitbrush is a common shrub that frequently grows in sagebrush-dominated habitats across much of the western United States. Rubber rabbitbrush (also known as gray rabbitbrush) and yellow rabbitbrush (also known as green rabbitbrush) are two species that are frequently found over much of southeastern Idaho.
Rabbitbrush is a priceless native shrub. According to legend, Native Americans utilized rabbitbrush for chewing gum, a yellow dye, and a therapeutic tea. Rubber rabbitbrush has different forage values. In some areas, it can be a significant winter and fall forage species for jackrabbits, pronghorn, and mule deer.

Amur Honeysuckle

This type of plant is an invasive species that can outcompete native plants. Compared to other honey suckle species, this one blooms later. Animals can obtain food throughout the later months as winter approaches thanks to its late seed-bearing. It can be as tall as 16.5 feet and can have a wide range of diameters. Their bark is ridged, flaky, and rough. By obstructing the sunshine, they shadow the lower plants that grow beneath them.

Bittersweet Nightshade

Bittersweet nightshade (Solanum dulcamara), also known as woody nightshade, produces poisonous shiny red berries June through August. The beautiful purple and yellow flowers and smooth oval-shaped leaves make this plant fairly easy to identify. Bittersweet nightshade is an introduced species from Asia and is different than deadly nightshade, which is significantly more toxic. Fortunately, bittersweet nightshade has a strong, unpleasant odor, so most animals will avoid it, and poisonings from this plant are not very frequent.
The entire plant contains solanine, the same toxin found in green potatoes and other members of the nightshade family.
How can a poisonous plant be useful to humans? Some people process the stalk, which has a lower amount of toxins than the rest of the plant, and apply it to the skin to improve conditions including eczema, itchy skin, acne, boils, broken skin, and warts.
Learn more here.

Poison Hemlock

Poison hemlock (Conium maculatum) stems have purple spots and streaks, are not hairy, and are hollow. Leaves are bright green, fern-like, finely divided, toothed on edges and have a strong musty odor when crushed. Flowers are tiny, white and arranged in small, umbrella-shaped clusters on ends of branched stems.
Poison hemlock is acutely toxic to people and animals if ingested. All parts of the plant are poisonous and even the dead canes remain toxic for up to three years. The amount of toxin varies and tends to be higher in sunny areas. Eating the plant is the main danger, but it is also toxic to the skin and respiratory system. Help kids learn what poison hemlock looks like so they can avoid playing in it.

Poison Ivy

“Leaves of three, let it be!” is an old adage that all Greenbelt visitors should heed. Each leaf of the poison ivy plant (Toxicodendron sp.) as three glossy leaflets, with smooth or toothed edges. Leaves are reddish in spring, green in summer, and yellow, orange, or red in fall. May have greenish-white flowers and whitish-yellow berries. Poison ivy is a native plant that grows along the Greenbelt and provides habitat for small animals. All parts of the plant contain the oil urushiol, a substance that typically causes allergic reactions on contact with skin.
Help kids learn what poison ivy looks like so they can avoid its irritating oil. If you suspect you’ve come in contact with poison ivy, rinse the area with cold water (river water is perfect!) as soon as possible.
Learn more here.

Horsetail

Horsetail (Equisetum arvense) plants are found worldwide and are unique in that they don’t produce seeds! Instead, they reproduce by releasing spore into the air in the spring. Since the stalks are coated in silica, they have been traditionally used for scouring metal and wood in cultures around the world.
Horsetails are dinosaur plants! Horsetails originated from a group of ancestors that were the dominant plants during the Paleozoic era. The ancestors of the horsetails you see along the river could’ve been tasty snacks for a triceratops!

Oregon Grape

Despite its name, Oregon grape (Berberis aquifolium) is native throughout the entire Pacific Northwest, including right here in Idaho along the Greenbelt! Its leaves are spiky, and often confused with holly. The plant makes clusters of yellow flowers in the spring, which turn to dark purplish-blue berries in the early summer. The berries are not poisonous but taste bitter (never eat anything on the Greenbelt just in case it’s been sprayed). Oregon grape berries are a yummy treat for birds and rodents.

Mullein

Mullein (Verbascum thapsus) leaves are fuzzy and are sometimes confused with the lamb’s ear plant. Lamb’s ear looks similar but is low to the ground. Mullein grow into large stalks of yellow flowers after the plant’s second year of life. The stalks can grow up to 10 feet tall!
Mullein has been used by people around the world to treat cough, sore throats, and more. The soft leaves can be used as a natural toilet paper if you’re far away from a restroom when hiking or camping!