Summarize this article in one sentence.
Trees are rarely symmetrical, so one side always seems to have more growth than another. Because plants need sunlight to grow, the side that gets the most sunlight will usually appear heavier. In the Northern Hemisphere, the sun spends most its time in the southern part of the sky, so the denser side of the tree will usually be facing south. In the Southern Hemisphere, the heavier portion of the tree usually points north. In order to accurately decide which side of the tree is the heaviest, you should walk all the way around it a few times. If you only look at one or two sides, you may not be able to tell where the tree is most dense. It's easiest to use this method with lone trees in an open field. In a wooded area, trees compete for sunlight, so it's not as obvious which direction they're growing in. In many cases, moss tends to grow on the side of the trees that is most shaded. In the Northern Hemisphere, that means you would usually find moss on the side of the tree that points north. In the Southern Hemisphere, you would typically find moss on the side of the tree that points south. It's important to keep in mind that other factors can create shady conditions that would encourage moss to grow on a certain side of a tree. Trees that are shaded by other trees in a wooded area and trees that grow on slopes may throw off your direction. This cactus, which is native to the southwestern United States and northern Mexico, grows slanted toward the south. That's because the northern side of the plant is mostly shielded from the sun, so it grows more quickly. If you spot a giant barrel cactus, you'll know the direction that it's growing toward is south, so the opposite direction is north. The giant barrel cactus typically grows between 3- and 9-feet, and features spines in a variety of colors, including red, tan, and yellow. Older cacti often produce bright orange or yellow flowers.
Evaluate the trees for their heaviest side. Look for moss on trees. Look for the giant barrel cactus in the desert.