If you look up ‘Growing an avocado from a seed”, you’ll be served with countless images and articles about sticking toothpicks in the pit and putting the bottom half in water. Works well enough if you are lucky. But let me tell you about a 5/7 technique that works 100% of all the times.
The main issue with handling any plant seed is that you must ensure as little contamination as possible — unless you are planting directly in soils— and even then most commercial crops are certified free of any crop-specific pests such as rots, mildew and even viruses . There’s really no need to jeopardize your plant right from the start if you can avoid it.
At home it’s another story — you get back from the shop with your fruits — cut them open to eat the flesh and probably wound the outer shell of the seed while doing so. That single slice to open the fruit brings potential pathogens from the outside of the avocado straight to the seed, which is a bounty of food for microbes. So how to avoid that?
Clean and clean again — once the pit is free from flesh, clean it with a sponge under running water and use a little dish soap and scrub well. That will take care of most microorganism on the surface of the pit. But the truth is that this thin brown shell is as much a cover as a source of potential pathogens, so you need to peel it off.
Once the seed is clean and free of its cover, cut away 5mm of the bottom of the pit and 1cm of the top. To identify what is the bottom and what is the top, look for irregularities in the structure of the seed (each seed is different) at each end — the bottom is where the roots will come out and is comparable to the human navel — it’s also the side of the seed which point towards where the fruit was attached to the branch of the tree (the peduncle).
Once your seeds are cut, you can clean them again with soap dish diluted in water — then rinse well. Place them in a container, the bottom of the seeds should sit on the bottom of the container and put enough water so that half of the height of the seed sit under the surface. Place a cover to prevent any contamination and let them sit in a warm place (I use the top of my fridge). If you have cleaned the seeds well, you won’t have to bother about them before they have roots and a small stem and are ready for transfer to soil. It might happen that bacteria start developing inside the container — this will translate into an opaque slippery film on the sides of the container and on the surface of the seeds. If this occurs, it’s better to change water, clean the container and rub the film off the pits with your fingers under running water.
There’s no strict rule to follow for knowing when you should transfer the seedlings to soil. I tend to grow them in batches and put them tangled altogether in soil. That makes a nice avocado bush! Okay now go try it out and grow some stuff!