Clearweed (Pilea sp.)

by cazort

Clearweed, or Pilea sp, are weedy annual plants in the nettle family, but without stinging hairs. Learn how to cultivate these plants in a natural garden setting.

Clearweed, or Pilea sp., are common annual plants native to Eastern North America, found in wet, shady areas. The plant's name comes from the unusual translucency of the leaves and stem.

Most clearweed is from the species Pilea pumila; less common is Pilea fontana, which is hard to distinguish. The plants are in the nettle family, but do not bear stinging hairs like true nettles.

Although they bear "weed" in their name, these plants can be attractive, and can be useful as part of naturalized or native plant gardens. Like most native plants, they support native insects, which for these plants, include some beautiful butterflies.

Below you will learn how to identify these plants, as well as how to cultivate them in your garden.

Identification: Compare To Stinging Nettles

Look for leaves with pronounced teeth, arranged oppositely along stems, and translucent stems and leaves, both hairless.

Clearweed is distinctive and easy to identify.  The leaf shape and growth habit resembles stinging nettles.  The leaves are fairly broad, are simple, and have fairly large and regular teeth, and are arranged oppositely along the stem.  Each leaf has three prominent veins.

Unlike other plants of the nettle family, clearweed lacks stinging hairs: the stem and leaves are hairless.  Clearweed also has conspicuously translucent stems and leaves.  The foliage often looks shiny.

These plants are small relative to other members of the nettle family, typically reaching a max height of 2 feet, usually much less.  Early in the season, they will be only a few inches high.

Clearweed (Pilea sp.)
Clearweed (Pilea sp.)
Photo by Alex Zorach
Clearweed Flowers
Clearweed Flowers
Photo by Alex Zorach

Are you familiar with this plant?

Growing Conditions and Life Cycle

Clearweed is happiest in light shade and wet conditions.  It likes poorly-drained areas, and can tolerate standing water temporarily, but cannot live in permanently flooded wetlands.

As an annual, clearweed dies down each year, but it can form persistent colonies through self-seeding.  The plant doesn't usually get very large; maximum height is usually around 2 feet, but it is common for plants to only reach about 6-12 inches in height.

The root system is weak and shallow, forming a small clump at the base of the stem.  The shallow roots are connected to this plant's preference for wet areas: the plant will wilt if the soil becomes thoroughly dry for too long.  Because of its weak roots, this plant is easily disturbed if weeding other plants growing in it.  Be gentle and take care to not disturb this plant if you wish to spare it while weeding.

Clearweed (Pilea sp.)
Clearweed (Pilea sp.)
Photo by Alex Zorach

Ecological Benefits: Supports Native Insects

Clearweed, being a native plant, supports a variety of native insects, including several attractive-looking butterflies that specialize on nettle-family plants.

The caterpillars of a number of different butterflies, ones that specialize in plants of the nettle family, feed on the plant's foliage, including the rather attractive Milbert's Tortoiseshell (Nymphalis milberti), Polygonia comma (Comma), the Question Mark Butterfly (Polygonia interrogationis) , and the Red Admiral (Vanessa atalanta).  For such an inconspicuous plant, these butterflies are quite visually striking.

The larvae of a rather interesting moth called the Beautiful Cosmopterix Moth (Cosmopterix pulcherimella) also eats the leaves. There is also an aphid, Pseudasiphonaphis corni, which feeds on the sap from the stem, and a leafhopper, Empoasca recurvata, that feeds on this plant among many others.

The following butterflies and moths are all supported in their larval stages to varying degrees by clearweed, or Pilea sp.
Milbert's Tortoiseshell Butterfly
Milbert's Tortoiseshell Butterfly
Question-Mark Butterfly
Question-Mark Butterfly
Red Admiral Butterfly
Red Admiral Butterfly
Cosmopterix pulchrimella Moth
Cosmopterix pulchrimella Moth

Cultivation and Use in Gardening

The neat, orderly appearance and interesting leaf shape and structure make this plant a useful and visually-striking landscape plant.  It also is useful as it thrives in wet, shady conditions that fewer plants like.  The flowers are wind-pollinated and are as such inconspicuous and easily overlooked; it is the foliage that makes this plant interesting to look at.

Because it is an annual, clearweed can only be grown persistently where the conditions are right.  If you want to grow it, scatter seeds or transplant a few plants to a wet, partially-shaded area of your garden, and you can let it form a colony, functioning a little like a groundcover.

Because it is shallow-rooted, it does not hold soil well.  It is thus best grown in flat, low-lying depressions surrounded by higher ground, or it can be mixed with deeper-rooted plants that hold the soil more effectively.

Colonies of clearweed have a very regular, orderly appearance when viewed from a distance, like in this photo. This can give the plant a groundcover-like effect.
A Colony of Clearweed
A Colony of Clearweed
Photo by Alex Zorach

So, what do you think?

Now that you know about this plant, would you want it in your garden?

References & Further Reading

Read more about these plants, or check sources to verify specific information.

My Pages on Other Plants

Learn more about native plant gardening, with a special emphasis on shade gardening.
Plants of the acalypha genus, with a focus on Eastern North America, and a mention of other species.
Shade tolerant asters, which grow, thrive, and bloom in part shade to full shade, in Eastern North America.
Nimblewill, a grass native to North America; uses for this grass in lawns and advantages to using this grass over other grasses.
Updated: 07/03/2016, cazort
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cazort on 08/05/2014

Yeah! A lot of "weeds" have a lot of ecological value, and it can be a shame when people pull them out, because they often replace them with non-native plants that don't have much ecological value or may even harm local ecosystems.

I'm trying to help people both appreciate native weedy plants for what they are, and learn how they can attract and support natural beauty, like butterflies. I'm thinking of adding some pics of the butterflies that eat this plant, to this page.

cmoneyspinner on 08/05/2014

Interesting. Make you appreciate the value of a weed plant.

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