Woody Herbs – What are Woody Herbs ?
When a herb is found to use wood as its structural tissues, it is referred as a woody herb. Woody herbs are generally perennial herbs (which lasts for an indefinite or longer time).
How is the wood produced ?
The wood is produced adjacent to the vascular tissues (the group of tissues that conduct water and nutrients for the herb). This wood is found reinforced into the stems and the relatively larger roots.
Functions of wood in Woody Herbs
Trees, shrubs or Liana’s are generally categorized under woody plants.
- The roots, main stem and the larger branches are covered by a thickened layer of bark. Wood acts as an adaptation which enables regular growth of the plant every year above ground stems. This makes a few of the trees tall and large.
- Every year newer woody tissues are formed, thus, increasing the diameter of the stem every year. The newer woods get deposited under the bark and on the outer parts of the stem. But in a few plants like Palm, the wood is deposited within the trunk (at the centre of the stem).
- The primary composition of the woody stems includes structures of cellulose (a compound carbohydrate) and lignin (a compound polymer helps in improving the cell strength). These compounds help in providing support and a vascular system to the herb. These compounds help in transferring water and nutrients from the roots to the leaves and channelize sugars (carbohydrates) from the leaves to the rest of the plant.
- The woody composition protects the stems from sudden shocks and environmental calamities.
Growth of the Woody structure
Growth in Annual herbs
Woody stem formation starts from the very first years of growth in a few of the annual plants (the plants with a life cycle lasting for an year i.e.- from seeds to blooms to seeds again). In these plants, the woods again die at the end of the growing season. They lack the covering of the dead cells (called bark).
Growth in Woody herbs
A few of these plants may not have the bark, but do have hard stems with vascular tissues. Such plants include Uraria picta etc. These are not perfectly woody but have tissues which are densely packed at the stem. Thus, they appear as hard as wood.
Growth in herbaceous plants
Others contain woody stem, which is thickened at the base and are called caudex. These include plants growing in dry or alpine climates.