What is bur cucumber?

Bur cucumber is a native annual vine in the gourd family, a wild cousin of the cucumbers and squash in your garden. Quick bur cucumber identification matters because the vine can go from a seedling in June to a blanket over a shrub border or fence by August.

Being native doesn’t make it polite. It climbs with curly tendrils, piles leaf on leaf, and can pull down young trees and smother whatever it climbs. Farmers along river valleys know it as a tough weed in corn and soybeans.

The good news is that it’s an annual. Every plant dies at the first hard frost, and new ones only come from seed, so if you keep plants from setting burs for a few years the problem shrinks.

Bur cucumber identification: what to look for

Bur cucumber looks a lot like a garden cucumber that escaped and went wild. Look for these features:

• Leaves: large, alternate, roughly heart-shaped to five-sided, with three to five shallow pointed lobes and small teeth on the edges. Both sides are rough with stiff hairs, so they feel like sandpaper.
• Stems: ridged and covered with sticky or bristly hairs.
• Tendrils: curly, branched tendrils at the leaf joints that wrap around twigs, wire and other plants.
• Flowers: small, greenish-white, five-petaled flowers on stalks from the leaf joints in mid to late summer.
• Fruit: tight clusters of small, oval, bristly burs, each holding a single flat seed. The bristles prick bare hands.
• Seedlings: big, thick, oval seed leaves, followed by true leaves that look like cucumber seedlings.

Where it grows in Pennsylvania

Bur cucumber likes rich, moist soil and full to partial sun. In Pennsylvania you’ll find it on stream banks and river floodplains, along field edges and fencerows, at woods edges, and in yards and gardens that sit low or close to water. River valley farmland is classic territory for it.

Floodwater spreads the burs downstream, and they also travel on equipment, in soil and on clothing. If your property sits along a creek or a river flat, expect it to show up again after high water even if you cleaned it out the year before.

Bur cucumber look-alikes

Several summer vines get confused with bur cucumber:

• Wild cucumber (Echinocystis lobata) is another native annual. Its leaves are smoother and more deeply cut into a star shape, it has showy upright plumes of white flowers, and its fruit is a single spiny pod about two inches long that dries papery and hollow, not a cluster of small burs.
• Mile-a-minute vine has triangular leaves, backward-hooked prickles on the stems, a round leafy collar around the stem and metallic blue berries.
• Japanese hops has deeply lobed leaves in pairs and hooked prickles on the stems, and it climbs by twining rather than with tendrils.
• Morningglories twine without tendrils and have funnel-shaped flowers.

How to get rid of bur cucumber

Because it’s an annual with a shallow root system, bur cucumber is one weed where pulling it yourself is often the best answer. The trick is timing and follow-up.

Hand and mechanical. Pull seedlings and young vines in June and July, before they flower. They come up easily from moist soil. For a vine already draped over a shrub, cut the stem at ground level and let the top wither for a few days, then pull it off; that’s easier on your plants than ripping green vines down. Wear gloves and long sleeves, because the bristly stems and burs irritate skin. New seedlings keep emerging through the summer, so walk the area every couple of weeks until September.

Cultural. Bare, disturbed soil is an invitation. Keep beds mulched 2 to 3 inches deep, keep turf thick and mowed along field edges, and plant or let desirable groundcover fill in creek-bank areas. Mowing an open area before plants flower stops seed production.

Chemical. Herbicides are rarely needed in a yard. On larger areas, extension recommendations for this weed include glyphosate spot treatments on young vines (it will kill any plant it touches, including your shrubs) and growth-regulator broadleaf herbicides such as 2,4-D, dicamba or triclopyr where the label allows. Treat small, actively growing plants, not vines already tangled through ornamentals. Read and follow the product label, because the label is the law, and make sure the product is labeled for your site; near streams you need a product specifically labeled for use near water.

Applying herbicide for hire in Pennsylvania requires a PA Department of Agriculture pesticide applicator certification, so a big creek-bank or field-edge job belongs with a licensed vegetation-management company.

Keeping it from coming back

The whole game is seed. Bur cucumber seeds have hard coats and can sit in the soil for years, so you’ll see some plants for several seasons, but each year you stop seed set you draw down that bank.

Walk your creek bank, fencerows and shrub borders in early July and again in August. Pull anything with sandpapery cucumber leaves before it flowers. Bag vines that already have burs rather than leaving them on the ground.

Keep bare ground covered with mulch or planting, and after a flood, check low areas soon after the water drops, since that’s when new seed arrives.

Questions we get about bur cucumber

Similar weeds

Mile-a-Minute VinePersicaria perfoliataJapanese HopsHumulus japonicusIvyleaf MorninggloryIpomoea hederacea