Monkey puzzle

 Avocadoes. I am trying to grow avocadoes in my polytunnel and outdoors. I managed to obtain Del Rio avocado seeds and 5 seedlings are growing under plastic. They survived the winter but the smaller ones suffered more than the larger ones so i wonder if it's the seedlings size or if some are hardier. 

This is the biggest and also the best looking Del Rio seedling after the winter. It had the least leaf damage.

One of the two small seedlings that both suffered most damage.

And the second small one.

Then there is two medium sized ones 

They both look pretty good so i am asking myself if the size determines hardiness or if hardiness determines size.                                In other words, has the largest of the 5 seedlings the least leaf damage because it's larger, (and then the other ones could be the same when they get bigger) or did its inherited frost resistance help it along all the way and that's why it's the best one in shape?

In any case here is a picture of my older fantastic seedling, also in the polytunnel and it got hit a lot harder than the Del Rio seedling.

In comparison the seedling survived the winter under plastic much better than the two year older fantastic seedling.

As far as my two outdoor avocadoes are concerned there is hope.

The mexicola seedling died back as it does every year after winter but my second outdoor plant that was also a fantastic seedling is still alive. I did protect it during a cold spell last year.

Mexicola seedling. Dead after winter outside. Was also protected when it froze.

Outdoor fantastic seedling survived winter for now, but i am really thinking of protecting it now to help it grow stronger.

This plant is the first avocado for me that does not die back to the roots every winter

This is a few weeks older picture of the stem of that plant and you can see that it grew on from the stem and not back from the roots.

Because this is the first time that i found an avocado plant that stands a chance of growing outside here it makes sense to me to look after it well and to try and help it grow strong. It is a fantastic seedling of a tree that was growing next to fruiting Wilma and Opal varieties in the same garden. 

So thinking about it, the older fantastic seedling seems to provide the answer. The best looking Del Rio seedling is the hardiest (least leaf damage after winter)