Botanical description: There are many wild lettuces, the easiest of which to identify is prickly lettuce for its conspicuously lobed leaves, sharp-toothed margins and spines on leaf undersides. Lactuca serriola is annual or biennial herb growing to five feet tall, with distinctive, milky sap. While native to Europe, it has been introduced worldwide including throughout North America. It has a single, hollow upright green or white stem that commonly grows from rosette of green leaves. The flower heads are grayish-yellow and seeds are equipped with a feathery pappus which facilitates wind dispersal. Nutrient rich soil and full sun are ideal site conditions, but it is a prolific colonizer of disturbed habitats and often grows along sidewalks and roads, capitalizing on the increased heat and helping to slow the flow of rainwater and sediment entering storm drains. Prickly lettuce is also well known as an edible plant, the wild relative of our domestic lettuces. The young leaves are edible raw or cooked, but the whole plant become bitter as it gets older. It is used as an asparagus substitute and edible oil is obtained from the seed. The plant has also demonstrated phytoremediation properties by absorbing heavy metals and binding them to organic matter.