Gardening often presents challenges when cultivated plants grow near wild look-alikes. Home gardeners frequently discover a large, leafy plant with reddish stalks that looks remarkably like domestic rhubarb (Rheum rhabarbarum) growing uninvited. This visual similarity is a common source of confusion. Misidentifying a plant that appears to be rhubarb can lead to poor garden management or expose a person to health risks. Understanding the subtle distinctions between these look-alikes is necessary for plant safety and effective weed control.
Identifying the Rhubarb Look-Alike
The plant most frequently mistaken for cultivated rhubarb is Great Burdock (Arctium lappa), sometimes informally called “wild rhubarb.” This widespread biennial thrives in disturbed soils, often appearing in gardens and neglected areas. Burdock completes its life cycle over two years. Confusion with rhubarb is most common during the first year, when the plant grows a large, rosette-shaped cluster of leaves low to the ground.
During this initial stage, burdock produces a massive, thick taproot and basal leaves that can reach up to 18 inches across. The leaves are heart-shaped and supported by thick petioles, which connect the leaf blade to the base. This impressive size, along with the reddish or purplish tint on the stalks of some young specimens, often leads the untrained eye to assume it is a young rhubarb plant.
Visual and Structural Differences
Telling the two plants apart requires a close inspection of their physical structures, focusing on texture and cross-section. The most reliable difference lies in the leaf stalk, or petiole. Rhubarb petioles are characteristically solid and fleshy, possessing a smooth, firm texture throughout their length. Conversely, Burdock petioles are often hollow or partially hollow, especially closer to the base.
The leaves themselves offer a clear distinction in texture. True rhubarb leaves are generally smooth, sometimes waxy, and a deep, glossy green color. Burdock leaves are typically dark green on the top surface but have a pale, woolly, or hairy underside. Feeling the underside of the leaf is a quick way to confirm the plant’s identity.
Examining the root system reveals another fundamental difference between the two species. Rhubarb grows from a large, perennial, fleshy rootstock that is more rhizome-like and spreads out over time. Burdock develops a single, thick, long taproot that grows deeply and straight down into the soil. This substantial taproot stores the energy the plant needs to produce flowers and seeds in its second year.
The Importance of Correct Identification
The distinction between cultivated rhubarb and wild burdock is significant due to both edibility and gardening concerns. The stalks of rhubarb are a popular food source, but its large leaves contain high concentrations of oxalic acid.
Ingesting these leaves can lead to a condition called hyperoxaluria, which causes severe gastrointestinal distress. In high enough doses, this may contribute to the formation of kidney stones or even kidney failure.
Burdock root, on the other hand, is considered edible and is used in traditional medicine and cooking, particularly in some Asian cuisines. However, consuming the wrong part of the wrong plant can have consequences. Mistaking the toxic rhubarb leaf for an edible wild green, or failing to remove the invasive burdock from the garden, presents real problems. The primary risk is consuming a toxic amount of oxalic acid from rhubarb leaves.
Beyond the health risks, misidentification impacts garden maintenance. Rhubarb is a contained, cultivated perennial that is harvested and managed. Burdock, by contrast, is an aggressive, invasive weed that can quickly take over an area. Its deep taproot makes it highly resilient and difficult to remove once established.
In its second year, Burdock produces distinctive purple, thistle-like flowers that mature into seed heads known as burrs. These burrs are covered in hooked bristles that easily cling to clothing and animal fur, which is the primary mechanism for the plant’s prolific and widespread seed dispersal.
Managing the Invasive Plant
Once the plant is correctly identified as Burdock, management must focus on eliminating the deep taproot and preventing seed production. The most effective method for control is manual removal, which must be executed with precision. Simply cutting the plant off at the base will allow the large taproot, full of stored energy, to regrow.
The entire taproot needs to be dug out completely, especially in the first year when the plant is still in its leafy rosette stage. Using a specialized digging tool or a sharp spade to cut the root well below the soil surface is necessary to ensure the plant cannot regenerate. Watering the area beforehand can help loosen the soil, making the difficult task of extracting the entire root easier.
If the plant is discovered in its second year and has already started to develop a flowering stalk, the immediate priority shifts to preventing the formation of burrs. All flowering stems must be cut and bagged for disposal before the burrs mature and scatter their seeds.
For large infestations, chemical control may be considered. The best time to apply a broadleaf-specific herbicide is early in the spring or in the fall. This timing is when the biennial plant is actively moving nutrients down into its taproot, which allows the herbicide to be effectively translocated to the root system, ensuring complete eradication.