Tunicate bulbs are some of the most familiar bulbs we come in contact with both in and out of our gardens.
Many underground plant structures are generally named bulbs. A definition of a bulb is a plant that incorporates its entire life cycle in an underground storage unit. Technically true bulbs are compressed stems surrounded by fleshy leaves acting as food storage organs. They are in the Monocot family of plants.
Bulbs can be further classified by looking at their various growth habits. Some of these “bulbs” are actually further classified as “true” bulbs, corms, tubers and rhizomes. Examples of these bulbs respectively are: narcissus, crocus, dahlia and canna.
True bulbs are represented by two classifications, tunicate and imbricate as represented by onions and lilies in that order.
Tunicate bulbs have a dry thin paperlike sheath surrounding them which helps to prevent them from drying and improves their storage capability. The basal base plate along with the tunicate sheath hold the bulb together. Roots emerge at the bottom of the basal plate.
We enjoy these bulbs both in the kitchen and in our gardens. Our cooking is enhanced by the addition of the tunicate bulbs of onions, garlic and shallots. The joyous colors in our early spring gardens are presented by our daffodils, tulips and hyacinths.
Graphite Drawing of Onion and Garlic bulbs
The term “bulb” is used by most people to refer to plants that have underground, fleshy storage structures. Only some of the plants commonly called bulbs actually are bulbs. The general definition of a bulb is any plant that stores its complete life cycle in an underground storage structure. These underground storage structures store nutrient reserves to ensure the plants’ survival.
Tubers, rhizomes, corms, and bulbs actually all serve the same purpose, just in a different way. They are each a storage unit for food that gives the plant the energy it needs to grow, bloom and complete its lifecycle each and every year.
The energy is created and stored by the foliage’s photosynthesis. You’ve probably heard that it’s important not to cut back the foliage after the bloom has died. That is because the leaves need to have time to absorb energy for next year’s bloom. Each storage system takes differing amounts of time to perform this task. Examples would be Alliums and Daffodils.
Bulbs or bulb-like plants are usually perennials. They have a period of growth and flowering. This is followed by a period of dormancy where they die back to ground level at the end of each growing season.
As with perennials, there are bulbs that are hardy in our climate and others that must be overwintered as house plants or placed in dormant storage.
Bulbs can be broken down into five types of storage structures. These include: true bulbs, corms, (stem) tubers, tuberous roots and rhizomes.
“Leeks and Pearl Onions” a graphite drawing by the Artist Mary Ahern
Bulbs (which are referred to as “true bulbs”) grow in layers, much like an onion. At the very center of the bulb is a miniature version of the flower itself. It is composed of a shortened stem covered with modified leaves called scales. Helping the bulb to stay together is something called a basal plate, which is a round, flat area that are the beginnings of the roots on the bottom of the bulb.
Many plants such as daffodils form new bulbs around the original bulb. These bulbs, called offsets, develop from buds within the base of the mother bulb and produce new plants. When these bulbs become overcrowded, the flowers start to diminish in size. This is an indication that it is time to dig up and divide the bulbs.
Examples of True Bulbs: Tulips, Daffodils and Alliums commonly known as Onions
After I finished the drawing I cut up the onion and put it in a stir-fry for dinner. Yummy!
TRUE BULBS ANATOMY
The true bulb has five major parts.
BASEL PLATE: bottom of the bulb which hold the bulb together and from which the roots grow
primary storage tissue
skin-like covering that protects the fleshy scales
consisting of developing flower and leaf buds
develop into bulblets or offsets