When walking in the forest or any natural or wild area, you're likely to come upon some plants with thorns. You may have discovered this by accidentally brushing up against one and getting scratched or poked, or you may have seen the thorns and steered clear. Thorns may be present on the stems or leaves of a plant, and they are a natural defence mechanism the plant uses to keep its enemies at bay.
Wild thorny shrubs grow in almost all climates. Japanese barberries have small green leaves and tiny red berries, and are invasive in the Northeastern U.S. Various Mahonia species, having sharp holly like leaves, are native to the Pacific Northwest. Common buckthorn has thorns on the branch tips, and are invasive in some states. Devil's walking stick is a ferny shrub having thorns along the stems. It's found in the Southeast.
Thorny Plants With Edible Fruit
Thorny plants can be a useful source of food for animals and human being alike. Many wild blackberries are invasive, but produce delicious berries. In the same family are salmonberries, wineberries and thimbleberries, native to the Northern U.S. Wild quince are found almost everywhere, and while they produce fruit, the fruits are rather astringent. Both the natal plum and the Chicksaw plum are large shrubs or small trees and produce small round juicy fruits.
Thorny Plants With Showy Flowers
Thorny plants that have fruit, edible or not, also have flowers. Sometimes they are rather showy, like the wild roses. All have thorns along the stems. Roses found in the wild include the Carolina, Virginia, Nutka, wood, swamp, and prairie roses. Hawthorns have thorns along the stems, and can be large shrubs or small trees. They have groups of small white flowers on the branch tips, and while pretty, they tend to have a musky smell. Mimosa has thorns along the stem, and the flowers are like pink puffballs. They also close their leaves when touched.
Some thorny shrubs now found in the wild started their lives in cultivation. Plants may have been brought to a new location where climate and other factors encouraged its growth. Foraging animals may spread seeds outside cultivation. Sometimes non-native species were brought in intentionally because a plant had a certain desired quality, like fast root growth for slope stabilisation. Because they had few natural restrictions they flourished, escaped cultivation, and often overtook native vegetation. Some examples are Natal plum, which is now considered invasive in some states, as is Himalayan blackberry and thorny olive.