Cuttings are a great way to multiply your plants for free. If you do it right, many plants will grow new roots and turn into a whole new plant just from a clipped stem. This time of year, as your plants are sprouting vigorous new spring growth, is a good time to take what are called softwood cuttings. That's just a jargon-y way of saying that the part you clip and root is new flexible growth, as opposed to hardwood (a.k.a. woody or older) stem cuttings that you would take in late summer.
The main advantage of propagating from cuttings is that the new plants will be genetically identical to the parent plant. Many varieties of plants don't grow true from seed (meaning that if you save seeds and replant them, the baby plant won't be at all like the parent) and must be reproduced by cuttings. Most mints and lavenders are this way, along with the popular chocolate cosmos, and all named apple varieties. (Though apples tend to be grafted, where a cutting from one variety - the tasty fruit - is fused to a root of another variety, for vigorous growing.)
The disadvantage of cuttings is that they tend to die on you. They're even harder to start than seeds. Most seeds will germinate, and then it's up to you to care for the seedlings. But, depending on the plant variety, a 50% success rate isn't unusual for cuttings. So as you take cuttings, mentally prepare yourself that even with the best care, many won't survive. That said, here's how to give them the best chance.
I'm using a rose pelargonium in the example below. Semi-succulent pelargoniums, often called geraniums, are a great plant to learn to propagate from cuttings. They're easygoing and have a high success rate. Why not start with an easy win? :)
1. Start by choosing vigorous new growth that looks healthy, and doesn't have a flower (or flower bud) on the end.
2. Cut off all but the top 2-3 leaves. This reduces the load on the nonexistent root system because the leaves are what suck up and use all the water. With fewer leaves, the plant needs less water and less root. Make a clean cut just below a node on the stem. Use sharp clippers or a sharp knife.
3. Quickly insert the cutting into a damp potting mix before the cutting has a chance to dry out. Seed starting mix is ideal because it's water retentive and drains well.
4. Firm it in gently so that the potting mix is in good contact with the cutting.
5. Repeat steps 1-4 with as many cuttings as you'd like to take. In this batch, I'm also planting two types of lavender, neither of which I know the name of, plecanthrus (which is another easy plant to root -- I'll have lots of this at the plant swap in April), plus two rose cuttings about which I'm not optimistic, but maybe if I'm lucky they'll root. It certainly doesn't hurt to try!
6. Label your cuttings, especially if there are several that look alike! (Yes, the sharpie washes off the glaze!)
7. Water the cuttings in gently. I like to use the "mist" setting on my hose nozzle. Water helps ensure that the cuttings are in contact with the potting mix.
8. If you're using an Orta self watering pot, fill the reservoir and set the cuttings aside in a bright, sheltered spot, out of direct sun for a few weeks to root. Check once a week to make sure there is water in the reservoir.
If you're not using an Orta pot, you'll have to check them more frequently to ensure that the potting mix is damp, but not soggy. Gentle daily watering is usually the best bet.
You'll be able to tell they have roots when they begin to sprout new top growth. Then you can gently remove them and repot them into a bigger pot.
Good luck and happy propagating!