Dunno the answer to your question. Don't suppose you know what cultivar it is? You could always try grafting other varieties onto the old geezer and see if you end up with better fruit. Avocados can be top-worked to essentially replace all the fruiting branches, but maintain the trunk. At 70 years, that thing must be pretty big!

Avocados don't ripen on the tree. You have to let them sit a few days after you pick them, but not in the refrigerator. They "mature" on the tree, but that isn't the same as being ripe. Odd, isn't it?

Here is a link that might be useful: harvesting avocados

I found a link that suggests maybe that it has not been grafted to begin with. If you grow one from seed the fruits will taste bleach, this link explains.

Here is a link that might be useful: avocado link

At the beginning of the season, they taste watery. It takes time for the oil content to rise to a level (around 20%) to make them taste good. The oil content rises, peaks, holds for a time, and then the oil begins to go rancid and the flavor becomes bitter. The fruit is reasonably ripe when the seed cover is a deep brown. A not so accurate indicator is when the stem at the connection point to the fruit is yellow. If the seed cover is pale or light brown, it is not ready. An indication of past-peak are black fibers visible in the flesh.

It may depend on what type of avocado you have. We have a very old Fuerte which is more bland in flavor than the Hass variety. I like it fine, but my husband doesn't like it.....as was mentioned earlier, you could graft (or have grafted) another variety or two onto it, I believe. We know that our tree is quite aways past 30 years old and the flavor does not change.

Thank you so much garden web community for all the great info!

@ yukkuri name - I never thought about grafting so I will definitely look into that.

@ lgteacher - got it about the ripening, they were unfortunately still tasting bad even after ripening off the tree

@ tropical thought - thanks for the link. I am definitely sure it was planted as a tree, and not from seed. The previous owners gave us a scrap book that showed their grandparents planting the tree in the yard back int the 40s

@hoovb - this info is great! Based on what you said, in september we definitely picked them to early. A few we had picked recently had the black fibers. I will check next time for the seed cover. What a bummer. I hope we did not miss the peak

@ wcgypsy - I I have no idea what variety this avocado is, but I will take one to the local gardening store and see if they can id the type. I included a picture below in case anyone in the forum can ID

Here is a link that might be useful: Pic of my avocados

It could be a Carlsbad, which is black when ripe, but many avocados are similar looking. You can tell if your tree was grafted by looking at the trunk near the bottom. It will have a bump.

I harvest mine when they get a glaucus coating at the top of the fruit- for my Hass tree, that's now until June. They start to taste rancid by August.
Renee

Here is a good page of photos of different common avocados. If your tree is very old, keep in mind some of these varieties are much newer than the 40s. Haas and Fuerte are the old standard cultivars.

Here is a link that might be useful: pictures of avocados

Thank you all for the help. It has been a year since we posted and we finally started getting good tasting avocados in the mid summer and had tons and tons come down through the fall. I see them starting up again though less so then the prior year. Perhaps this is an every other year tree. In any case, all we needed was a little time...

Glad you got some good avocados! It's not bad to have an every-other-year tree. After a while you get kind of avocadoed out, and need a rest from them.

Good to know! Thanks for checking back with everyone to give us the good news.