A hardy, thorny vine native to the world of Athas, the brambleweed is a plant dangerous due to its many sharp thorns. It is also useful because of this (and its hard, fire-resistant exterior), and so is frequently cultivated, formed into free-standing, thick stands known as brambletrees. For adventurers, their main note is that patches of them can protect areas quite effectively, and that wooden weapons made from their thickened, hardneed.
Each 10-ft. square of brambleweed has 1 HD, and clumps can be 100-10,000 ft. in size. Destroying it with weapons means hacking at woody stems that are AC 8. Destroying a 10-ft. area of the brambleweed is worth 15 XP.
A patch of brambleweed is dangerous due to its many long, sharp thorns. A victim who falls into a patch of brambleweed is subject to one attack roll by the plant (THAC0 20), and, if hit, they are hit for 1d100 points of damage, each point coming from one thorn. If they survive, they have managed to extract themselves from the weed.
The deadly thorns make the plant useful enough as a defensive barrier or obstruction that few would be willing to cross, but careful cultivation can also produce a large, vertical tangle of brambleweed, with thick, woody stems. These "brambletrees" can be turned into effective staves or clubs, dealing double damage when compared to normal clubs and staves. However, if the weilder fumbles the weapon, they are likely to hurt themselves on the thorns, so it is not gear that is easy to use. These weapons are also expensive, costing four times as much as a typical weapon of the type.
Only the ends of a brambleweed grow, and at the relatively rapid rate of 1' per day. The dry husks that remain of the other parts form a thick, woody, thorned trellis that protects the vine and allows it to seek sunlight and out-compete other plants in flat areas. A sprinkling of water in the morning and night (akin to dew) will effectively cultivate a brambleweed, and those who wish to harden a brambletree simply constantly trim the shoots, creating thicker and thicker branches. The hardened end of the brambleweed doesn't burn, meaning fire isn't as useful in dealing with this as it is when dealing with most woody plants.