Scott Grows an Avocado Tree

Should you germinate an avocado seed in soil or water? Is it faster to grow an avocado tree in soil or is the water and toothpick method best? These are – perhaps – age old questions of growing avocado trees. So I endeavoured to find out and I conducted an experiment. 

I really like trialling different things and conduction experiments – it’s one of the ways we learn things. So, a little while ago, I conducted an experiment with my YouTube audience. 

The experiment was to find out whether it was better to grow an avocado seed in soil or in water. I had two groups: a control group (that was in water) and an experiment group (that was in soil/potting mix). I then invited my audience to follow along at home and set up their own experiments and send me the results. I was thrilled to have folks from all over the world joining me for this international avocado experiment. 

We had six months to run our trials and see which was better. Our jobs were to monitor our seeds and see which one reached a height of 5cm first. It wouldn’t have been fair to do it from germination date because… when a seed is buried you can’t tell if it’s germinated or not. 

The experiment was run and this is what we found. 

First, let’s talk about the avocado trees reaching a height of 5cm in the six months. 

25% of the control (water) group reached 5cm in the six months, but the experiment group saw 87.5% of seeds reach 5cm in the six months. 

That’s 62.5% more than the water group! 

This indicates that growing avocado seed in soil is the faster and more effective way of growing avocado seeds. 

But why? 

Why do avocado seeds germinate faster in soil compared to water? I’m not entirely sure, but here is what I speculate: 

There are three things that seeds need (generally) in order to germinate, or start growing, they are: heat, water, and oxygen. 

• Heat: I didn’t use a thermometer on any of the samples, but I wonder if soil holds its temperature better than water. I can imagine that it would release heat more slowly overnight compared to water, hence increasing germination rates and speeds. 
  
• Oxygen: There is both atmospheric oxygen (in the air) and dissolved oxygen (in the water) getting to seeds in soil. Fluffy, well draining soil is well aerated, which should mean a higher level of oxygen getting to the seed. If water sits stagnant, the dissolved oxygen evaporates over time and water becomes lower in oxygen (note that this isn’t the oxygen from the water molecules that are evaporating – that’s a very, very different process).
   
• Water: Admittedly there is a lot of water in the water and toothpick method – but a seed doesn’t require full submersion in order to grow. So I propose that the extra heat and oxygen are more impactful for the rate of germination. 

So, we can conclude that it’s better to germinate avocado seeds directly in potting mix or soil compared to water. So why do grow avocado seeds in water? 

I think I know the answer: 

It’s because it’s cool. 

It’s such a wonderful thing to be able to watch an avocado seed start growing, from when it cracks, to when the roots start emerging and growing, and eventually a shoot begins to make its way upward. It’s so lovely to be able to see that happen – it’s almost magical. You don’t get to see the roots do their thing when a seed is buried. And avocado seeds do still typically grow in water – but perhaps less quickly. It’s fine to still grow ou avocado seeds in water, but once they’ve germinated, make sure you switch them into a well draining potting mix. Trees weren’t supposed to grow exclusively in water and soil provides nutrition and anchorage that water alone cannot provide. 

So to conclude, it’s faster and more effective to grow an avocado seed in soil, but it’s lots of fun to do it in water. Both ways work… it’s just that one works better. 

If you’d like to learn more, or see the samples of the various experiment trials. Check out the video I made on the topic. 

Thank you to the excellent avocado enthusiasts who participated in this experiments and whose images from their trials are in this blogpost. I appreciate it. You folks are legends.

Also, this experiment wrapped up 18 months ago… I’ve just gotten busy and doing the write up slipped my mind!