Leaf Cuttings
One day,
a leaf falls off your favourite plant. Maybe you knocked it a little too hard, and the petiole snapped... so, just out of sheer morbid curiosity, you stick it in a jar of water and hope beyond hope that it'll grow into a new baby plant.
From here, there are three possibilities, and what will happen depends entirely on what species of plant we're talking about here... because such is the magic of leaf cuttings.
Situation 1
Most plants require what is called meristem tissue to propagate from a cutting of any kind. This special tissue can grow and specialize into root tissue, shoot (stem) tissue, or leaf tissue, as is needed by the plant. For most plants, though, the main places where meristem tissue is located are the nodes, the places where the petioles (leaf stems) meet the main stem. Without meristem tissue, you're out of luck for most plants; the leaf may survive for a while, able to draw water through the petiole, but it will eventually decline and die.
Most houseplants will fall into this situation, including all aroids -- Monstera, Pothos, Philodendrons, etc.
Situation 2
This is actually the least common situation, but it's a step closer to a true new plant! For some species, just a leaf will be able to root... but not to create new "shoot" tissue, so it'll never grow -- just remain a rooted leaf. These leaves -- often called zombie leaves -- aren't super common, as I said; the most common species that you'll find as rooted zombie leaves in cultivation by far is the Hoya kerrii, or Heart-Leaf Hoya. As the common name implies, the Heart-Leaf Hoya's leaves are heart-shaped, which makes it a common sight around Valentine's Day. You can also create zombie leaves with fallen Ficus varieties, such as Ficus elastica, otherwise known as the Rubber Tree.
These leaves, despite sometimes extensive root systems, will never grow new shoot tissue -- new stems or leaves -- and will decline after a while, usually a maximum of a few years. To grow a new plant, you'll need a node for these plants.
Situation 3
This is the one you've been hoping for -- some plant species truly can propagate from just a leaf -- or even just part of a leaf, in some cases!
Species that can successfully be propagated from leaves include Peperomia species like Peperomia caperata, as well as Begonia species like Begonia maculata or Begonia 'Black Sky', among others such as the ZZ plant. For some species, such as the Watermelon Peperomia, you can propagate with just a section of leaf -- new plantlets can grow just from the veins.
So, how do you know?
Unfortunately, the answer is: do some research! If we have a full care guide, it includes a section on propagation that will include whether or not a leaf cutting will be successful.
If you're not sure, feel free to contact us and ask! We're always happy to chat plants.