Hello Friends! Today I'm going to teach you how to easily propagate potatoes and onions. Propagation is just a fancy horticulture word that means we are going take a single plant and create many. I'll also use it as an excuse to teach you a little bit about plant anatomy and biology. So, lets get started!
Step 1: Variations on a Theme: Organs Modified by Evolution
All vascular plants share the same, basic body plan. There is a node, where leaves attach to the stem. There are lateral buds that sit just above the leaf and the stem. And then there is a section of stem tissue between the next node which is called the inter-node. At the very tippy top of the plant there is a very special region known as the "growing point" but more technically called the apical meristem. This is a population of cells that actively divide and generate new tissue. Thats pretty much it for the above-ground portion. A plants body is made up of nodes, leaves, buds, and inter-nodes. This pattern of development (node, leaf, bud, inter-node) is repeated by the growing point over and over to create the ordered, patterned body of a plant. However, evolution has stretched and molded the standard theme into staggering variations form and function.
Step 2: Variation 1: the Potato
Potatoes are not roots. Although they grow underground, they are fundamentally stems. Take the potato you keep beside your desk and examine it closely. You'll find that it has polarity. That is, one end is different from the other. You will discover that at one end the "eyes" are much more abundant that at the other end. If you would take a white marker and connect the eyes to one another you would find that it produces a spiral that goes up and down the stately tuber. This is exactly how the leaves in many plant species (including potato) are arranged. Maybe one of the eyes is starting to bulge, and maybe if its an old potato you will find a new shoot emerging from this region. These are nothing like roots. Roots are hairy and branching and haphazard. This starchy friend is a stem. In the course of evolution, the internodes have become compacted and swollen. And instead of just carrying water and nutrients to different parts of the plant, these stems have started to bury themselves in the ground and load themselves up with carbohydrates to store energy for the next year. The "eyes" are actually the lateral buds that are attached to the node. Notably, this stem has no leaves attached but you can clearly see the mark evolution has left on this organ. you can see small, crescent shaped marks beneath the buds. These are vestigial, evolutionary hang overs. A mark that indicates this is indeed, a stem and that its ancestors had leaves that went there.
Step 3: Potatotipency
Plants are cool because nearly all of their cells are stem cells, and not just the ones in the stem. That is, every living cell of a plant has the potential to go on and continue to grow and develop into something new. This is a property that is referred to as "totipotency". The fact that plants cells are totipotent means that we can do really neat stuff with them and its essential to plant propagation. It means we can take a tissue, give it the required treatment, and have a totally new tissue type emerge . For example, we can take our stem tissue and encourage roots to grow where there were none before. This is amazing. It was as if we could take our hands, expose them to the correct environment, and sprout ears from our palms.
The nitty gritty:
Takeyour potato and start cutting it into smaller sections leaving at least one "eye" present in each segment. Leave it out for about 10 days to let the tender inside toughen up a bit. There are about 100,000,000 bacterial cells in each gram of healthy soil, many of which would love to eat a potato. The tough, corky skin will protect our seed potato from infection. The eye will sprout and become the main stem of our new potato plat. Roots are encouraged to form when we place the potato piece in a dark, moist environment such as the soil.
Step 4: Onion Propagation
Onions are neat little creatures. Again, they are a wonderful example of evolution taking a basic design and molding it to serve a new function. The bulk of an onion is actually highly modified leaf tissue. Take a gander! cut your onion in half down the center. At the very bottom you'll see what is known as the basal plate. The basal plate is a really really scrunched up stem. Emerging from the basal plate you will find the modified, fleshy leaves that are used to store energy. Cut the onion into quarters and tease apart the layers. You will find that they separate without much coaxing. each layer is a new leaf and a separate organ.
The nitty gritty: Take your quartered section and tease the layers apart. Gently pull the leaves from the basal plate. Place them in a tray of damp soil curved side up. The part of the onion that was at the bottom should be placed slightly below the surface - this is where roots will develop. Do not let them dry out. It helps to mist them every so often and keep them covered by a plastic bag.
Step 5: Success
This takes a fair amount of time, but plant propagation is fun, educational, and tasty. Be patient. Here I show an onion section that has developed successfully into a new plant. The end that was underground calloused over and new shoots and roots have emerged. You can transplant these outside as soon as the risk of frost is gone in your area.
Another cool fact: You have successfully cloned an organism at home. Each daughter will be genetically identical to its mother and retain its traits. This is how potatoes are commercially propagated - an outstanding spud is identified and multiplied ad nauseum. Just before the Irish famine, almost the entire island was planted with a single clone known as "lumper". Take that, Dolly!