Canadian Clearweed (Pilea pumila)

Aptly named for its translucent stem, clearweed is an annual edible plant in the nettle family. This small plant grows in clumps and colonies in moist, shady woods and forests. Also known as Pilea pumila, it has distinctive leaves and small yellowish green flowers.

I. Appearance and Characteristics 

Pilea pumila, commonly known as clearweed, Canadian clearweed, coolwort or richweed, is an herbaceous plant in the nettle family (Urticaceae). It is native to Asia and eastern North America, where it is broadly distributed.

This plant is most often found in rich loamy soil, usually in moist to wet areas. Its natural habitat is in forests or other lightly shaded conditions. It is a common plant throughout its range, and forms large colonies where it is found. It grows in both high-quality habitats and in ecologically degraded areas. Due to its high tolerance for disturbance, it is often seen near buildings and as a garden weed.

Pilea pumila is an erect annual, growing 0.7 to 70 cm tall. The foliage is opposite, simple with dentate margins, wrinkly (with depressed veins), ovate, and with long petioles. Both the leaves and stems are translucent and bright green, turning bright yellow in autumn. The flowers are small, borne in axillary cymes, unisexual with both genders occurring on the same plant, greenish yellow, and pollinated by wind. Flowers bloom from midsummer through early autumn. Fruits (achenes) are green with purple markings. Roots are fibrous, shallow, and adventitious off the stem in moist areas or when in contact with the soil.

The plant is often mistaken for stinging nettle (Urtica dioica), but can be distinguished by the lack of trichomes, or stinging hairs, and the lower amount of branching of the inflorescences.

II. How to Grow and Care

Sunlight

Pilea pumila does best in a bright, indirect sunny spot in your home. Even though this plant is part of the succulent family, do not place your plant in direct sunlight since it will scorch the leaves. In order to prevent your plant from growing lopsided, rotate it at least 2-3 times a week since it grows towards the sun. This plant can adapt to lower light areas, but the leaves will turn a darker green and the plant will spread out more.

The leaves that have been exposed to too much direct sunlight will sunburn and turn yellow. Trim sunburned leaves off of the plant and move the plant to a shadier location immediately.

Temperature

Normal household temperatures between 65-75 °F (15-23 °C) are fine. However, make sure that your Pilea does not sit near the heating vents in the winter, as it will drop its leaves. They shouldn’t normally survive temperatures lower than 50°F (10°C) in winter. It is best to grow the plant indoors, since, indeed, the slightest frost will kill it.

Watering

Isn’t too fussy about humidity, and although its leaves are succulent-like, it prefers more water than a cactus. Like a lot of succulent plants, it is prone to root-rot, so allow the soil to dry between waterings, as Pilea do not like soggy soil. Watch the leaves – when they start looking a tad droopy, it’s time to water your plant. During spring and summer, the top quarter inch of the soil should be kept moist. During fall and winter, allow the top quarter inch of soil to dry out before watering again.

If you notice white spots on your plant, they are most likely caused by salts and chemicals in your water. If you do not have a filtration system, leaving the tap water in an open container overnight before watering can help remove some of the chlorine and fluoride.

Substrate and growing media

Canadian clearweed grows best in smaller pots or planters where their roots will be somewhat restricted, choose a new pot that’s just one or two inches larger in diameter than the old pot. They should be planted in a peat moss based commercial potting mix with leaf mold and perlite added. Check the root density every spring, if the roots are becoming overly dense, transplant the plant to a larger pot. If you do not, the root system will break the container in an attempt to find more room to grow.

Fertilizing

For best results, use a general liquid houseplant fertilizer at half strength twice during the spring and summer. Do not fertilize a dry plant; instead water it first and then fertilize the next day.

 If a white crust develops on the soil, it’s a sign of fertilizer salt build up. If this occurs, hold off on your fertilization for a few months. In addition, make sure you’re flushing water through the pot each time you water. Evidence of salt buildup also shows up as a white crust on the outside of terracotta pots.

Pruning

Pinch the terminal stem (the topmost one) between 2 fingernails to force the plant to start branching out. If you wish for the plant to keep a bushy bearing and grow as many branches as can be, simply keep pinching young shoots off after a bud.

Blight (plant disease) can occasionally set up in a plant. It will usually begin in one leaf, turning it brown and rotten. Remove this stem from the plant to prevent it from spreading to the entire plant.

Propagation

Pilea pumila is super easy to take cuttings from, as it has the ability to grow roots and plantlets from almost every part of the plant! The easiest way is to take a leaf (with the petiole attached) from the mother plant, let the end dry out for a day or two, and then put it in a little glass of water, and watch and wait! Keep the water clean and make sure that the leaf isn’t allowed to dry out, and in 1-2 months, you should start to see new growth

III. Uses and Benefits 

Canadian clearweed is edible, but unpalatable. The plant can be used in classroom demonstrations of transpiration using food coloring due to its translucent stem. It was reportedly used medicinally by certain Native Americans for sinus issues, itch relief and to reduce hunger, and it is sometimes used as a diuretic in Asia.