Unlike sheep, plants are easy to clone. You don’t even need a fancy laboratory with lots of bubbling liquids and mysterious equipment. Many plants root very easily from cuttings, allowing you to quickly clone one plant into many identical copies. It’s also a good way to grow herbs like sage and rosemary from stems you buy at the market.
To make cuttings, you trim stems into two or three node pieces and insert them into a growing medium that drains well yet retains moisture. Keep them moist but not wet, give them bright light but not direct hot sun and be patient. If all goes well, you’ll see new growth. Wait until the cuttings develop into small plants to ensure that their root systems will support them in the garden, and plant them where you want them.
The easiest plants to propagate this way are in the mint family: rosemary, sage, etc. This includes native sages, so don’t assume that because something is in the mint family it’s automatically going to be an invasive water guzzler.
Willows are also easy, from cuttings made in early spring (at the “pussy willow” stage). Obviously, willow propagation is best reserved for larger properties doing native willow revegetation.
In a commercial setting, cuttings are propagated in a greenhouse using technologies like intermittent mist, bottom heat, and rooting hormones for a higher success rate. Some plants require all this in order to root at all. Since this can get pretty technical, with different rooting hormone formulas for different plant species, timing systems, heating systems, cold frames, etc. I’ll leave it up to you to pursue further. I’m happy with my simple technique that works well enough for the things I try to propagate.