Thaumcraft 4 adds a variety of vegetation to your Minecraft World. There are Greatwood Trees, Silverwood Trees, Shimmerleaf, Cinderpearl, Mana Pods and vishroom.
The information below is taken from the Thaumonomicon excerpts.
Greatwood Trees are large, majestic trees that dot the countryside. Their wood is able to absorb impressive amounts of magic, which makes it a popular component in the crafting of magical devices. If the trees have cobwebs around them, they will have a cave spider spawner and chest underneath. The logs are a plentiful source of Praecantitio essentia.
Greatwood can be crafted as any other wood, similar to any other wood. Greatwood is used in several crafting recipes, notably the Greatwood Wand Core.
Silverwood Trees are incredibly rare and are valued for their purifying properties. The trees will spawn in any biome, but are very rare in biomes other than Magical Forest.
The trees are very magical in nature and pure aura nodes are often formed within their hearts, which makes a silverwood sapling a prize beyond measure. Pure aura nodes will gradually transform the surrounding area into a Magical Forest, but only if they are still in their silverwood block. If moved, they will still revert Tainted or Eerie lands to the underlying biome, but not create Magical Forest. They are easily recognizable by their blue leaves. The logs are a plentiful source of both Praecantitio and Ordo essentia.
Silverwood can be crafted as any other wood, however, both logs and planks are marked as "transparent" blocks -- for example, fences will not attach to them, and they cannot pass a redstone current. Silverwood is used in a number of crafting recipes, including the Silverwood Wand Core.
As silverwood saplings can be planted, it makes it possible to create pure aura nodes indefinitely. However, the growth rate of the tree is slow and can only be sped up using the Lamp of Growth or other items from other mods(e.g. Watering Can from Extra Utilities 2). Using a Hoe of Growth on a silverwood sapling will instantly grow it.
Shimmerleaf flowers grow only in the shadow of a Silverwood Tree. In current versions, they only appear around naturally generated trees, not from silverwoods grown from a sapling. They can be crafted into Quicksilver (formerly, they dropped quicksilver whenever broken without shears). Shimmerleaf are used to make ethereal blooms, which combat taint.
Cinderpearls are found only in the hottest of climates, these plants burn with an elemental fire. They can be crafted into 1 blaze powder per cinderpearl. (Formerly they dropped blaze powder when broken without shears).
Cinderpearls cannot be farmed; once they have been harvested, they're gone, but they can easily found in desert biomes. It is easy for them to be found during the night because they give off light and can be spotted easily.
These plants are only found on trees growing in magical forests. They grow very slowly and only yield one or two beans when harvested. These are known as Mana Beans and contain concentrated amounts of essentia. Cultivation and farming of Mana pods is difficult and time consuming, but eating them can temporarily give you magical powers, as well as a chance for a research point for that aspect.
Vishrooms are found in Magical Forests. When touched, they inflict Nausea on their victim. The effect lingers for 10 seconds unless the victim drinks a milk bucket.
They shed light on their surroundings and have no known use (and cannot be farmed), but they can be distilled for their aspects.