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42 RUSSIAN THISTLE (Salsola tragus) PLANT DESCRIPTION Russian thistle, or tumbleweed, is a broadleaf summer annual weed that can be found from summer to fall as a 3–6 foot wide, round, bushy weed. Russian thistle can be seen in late spring as a seedling, or as a tumbleweed in late fall and winter. It is easily identified by its bushy, round form and small prickly leaves. LEAF: The leaves are waxy and resemble pine needles. They are green, narrow, fleshy, and have a single sharp spine at the tip. STEM: Russian thistle has many long branches that form its generally round shape. The stem is almost woody when the plant dries out after dying. FLOWER: The flowers are small, green to white, and fleshy. They grow at the base of leaves along the stem and are hard to distinguish from other plant parts. SEED: Seeds are the primary means of reproduction. Most seeds drop around the parent plant. Russian thistle frequently detaches from the root system, becoming a tumbleweed. As a tumbleweed, the seeds are dislodged from the flowers and fall to the ground as the plant tumbles across the landscape. REPRODUCTION: Seeds are the primary means of reproduction. Mature Russian thistle can produce hundreds of thousands of seeds that may be viable in the soil for one to two years. WHY IT IS NOXIOUS: The plant is not toxic; however, some people develop a skin rash from contact with leaf spines. Due to its prolific seed production and ability to spread the seeds over large distances, Russian thistle is capable of readily spreading onto adjacent lands. SEASONAL IDENTIFICATION WHEN TO FIND: Russian thistle is most noticeable during midsummer to fall after developing the round "tumbleweed" form. SPRING IDENTIFICATION = EASY TO MODERATE Young plants are fleshy and flexible. The leaves are very narrow, soft, flexible, and are most like pine needles at this stage. Seedlings may resemble grass sprouts or pine sprouts. SUMMER IDENTIFICATION = EASY Branches are long, highly divided, and can have red or purple stripes. Flowers are small, inconspicuous, and are formed singularly along the branches under the leaves. The new leaves are formed along branches and have papery margins with a sharp spine tip. FALL IDENTIFICATION = EASY As plants mature later in the year, the leaves, branches, and stem become stiff and woody, and new leaves are smaller than older leaves. Seeds also develop in the flowers. WINTER IDENTIFICATION = EASY TO MODERATE Russian thistle's stem will detach from the roots after it has dried and produced seeds. Russian thistle's form resembles a tumbleweed. Plant skeletons may be caught in other vegetation, fences, or other similar places. SIMILAR-LOOKING SPECIES KOCHIA (Bassia scoparia) can grow in a similar form but typically grows into a cone shape and its leaves are not armed with a spine tip. Kochia is soft to the touch. LOW HIGH ohio distribution roadside distribution growth seeds ability to dominate difficulty of control WHERE TO FIND: Russian thistle is uncommon in Ohio. It has been seen in northwest Ohio near railroad tracks, but not along the road. Look in dry, disturbed sites along roadsides near railroad tracks. CONTROL METHODS: MECHANICAL: Individual plants can be controlled by pulling or cutting in the spring up until seeds develop. CHEMICAL: Make directed applications to Russian thistle using non-selective herbicides with added surfactant in spring or summer when the plant is young and actively growing. CULTURAL: Install pavement where appropriate near roadway. RECOMMENDATION SUMMARY: Russian thistle is a summer annual weed that develops into a stiff form that is very drought resistant late in the growing season. For best control, make herbicide applications in the spring shortly after seed germination or summer when the plant is young and actively growing. Adding surfactant will help improve herbicide surface coverage and penetration into small waxy leaves. Russian thistle survives times of drought by conserving water and using its deep taproot to capture subsurface water. Refrain from making herbicide applications in times of severe drought, as this plant will be less affected by herbicides. Pull individual plants any time of year, but be careful not to distribute seeds after flowering. Failure to control Russian thistle will allow individual plants to produce hundreds of thousands of seeds that have the potential to germinate on some of the driest sites in Ohio. summer annual RIVM LEVEL OF CONCERN

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