The tumbleweed also called the Russian thistle is an interesting plant that separates from its roots when it is mature and tumbles away in the wind.
Generally, tumbleweeds can grow almost on any type of soil, but are most common in the semi arid continental climates of steppes.
There are a few plants in the world, which have the tumbleweed habit, and most of them are agricultural weeds. These plants are native to Eurasia and Russia, but in recent times have become common in North America.
Some of the plants that have the tumbleweed habit are the Anastatica, the North American desert tumbleweed, and some parsley varieties, plantain (banana) varieties, baby’s breath, and the plains tumbleweed.
The mechanism of disengaging from their roots comes after the plant has matured and the seeds are ripe. The tumbling habit of the plants is their adaptation to scattering ripe seeds for re-growth.
They are tumbled by the winds that are quite strong in the steppes and many different plants tumbleweed at different times during the season.
Tumbleweeds are generally considered weeds and they have become increasingly widespread in recent years, often taking advantage of habitats that have been disturbed by humans.
Studies have shown that many types of tumbleweed found in disturbed habitats like areas following weapons testing, actually soak up harmful chemicals like uranium from the soil. This means that these weeds are useful and that they are extremely resilient.
The seeds although they are short-lived, grow rapidly, and the plant produces at least 250,000 at a time. These germinate within a few days of being scattered all over.
These seeds are quite poisonous and therefore they do not become meals of herbivorous animals grazing in the region.
Tumbleweeds produce tube shaped leaves during seedling, which reduce the surface area for evaporation, just like cacti.
It also has a taproot that allows it to access moist soil within the earth, which gives it just enough nutrients to survive. Because of this, these plants do not adapt very well to very moist soil.
Another important adaptation of tumbleweeds is their C4 metabolism. This means that under low CO2 conditions, tumbleweeds are able to store CO2 in their leaves during the evening so they can use them during the day.
Because a high amount of moisture is lost during the day, tumbleweeds can close their leaf pores, protecting moisture loss without actually sacrificing their growth (because they are using stored CO2).