Orchids have held a place of fascination for mankind for many hundreds of years. From early European aristocrats that would go to almost any lengths to be the first to possess a rare orchid to today’s hobby growers and florists, orchids maintain a high popularity. While it is usually their jewel-like flowers that were being sought after, the orchid possesses many different and unusual attributes with one of them being the stem of the orchid. Even though there are 25,000-30,000 known species of orchids with more being discovered everyday, there are certain similarities (and a few differences) between the stems of different orchid species.
The stem of every orchid determines the habit of the species. Each type of orchid stem can grow in one of these two ways:
•Monopodial growth: This is also referred to as one footed growth. This means that the new shoots grow upward from a single stem that originates in the end bud of the old shoots. It then can produce leaves and flowers along this stem. The stem of these orchids may reach a length of several feet. This can be seen in the genera Vanda and Vanilla.
•Sympodial growth: This is also referred to as many-footed growth. These types of plants produce a series of adjacent shoots which grow to a certain size, bloom, then stop growing only to be replaced by the next growth. Plants of this type tend to grow laterally rather than vertically because they can then follow the surface of their support. The growth of the orchid is propelled by the development of new leads using their own leaves and roots and sprouting from or next to those of the previous year. This is clearly seen in the genus Cattleya. While the lead may be developing, the rhizome may start its growth again, this time from an ‘eye’, or undeveloped bud, on the stem thereby causing the rhizome to branch.
It is also interesting to note that all orchids are considered to be perennial herbs. This is due to the fact that they lack a permanent woody structure. Their structure as noted above also determines to a large degree their growing habitat.
An orchid is considered terrestrial if it grows rooted in the soil. Terrestrial orchids may be rhizomatous which means that they form corms or tubers. These corms or tubers act as storage organs for food and water. In addition, the root caps of terrestrials are smooth and white. Terrestrial orchids are found mostly in colder climates.
A great number of orchids are epiphytes, which means that they do not require soil, and they use trees for support. These types of orchids occur in mostly warmer regions. Epiphytic orchids also have modified aerial roots, and in the older parts of the root, an epidermis that has been modified into a spongy, water-absorbing velamen, which may have a silvery-gray, white or brown appearance. An interesting fact attached to these types of orchids is that the cells of the root epidermis grow at a right angle to the axis of the root. They grow like this in order to get a firm grasp on their support. These roots can sometimes grow to be a few yards long, in order to take up as much moisture as possible. For these types of orchids, nutrients mainly come from animal droppings on their supporting tree that are washed down when it rains.
Orchids can then be classified into two different types depending on the type of stem that they have and the connecting root system. There are both sympodial (many-footed)epiphytes and sympodial terrestrials. Most monopodial orchids are only from the terrestial family.