They are the nodules of what are called adventitious roots and normal. An indication that the root is looking for air.

But it is past time to get that planted into some potting mix ASAP so some feeder roots will develop. They won't grow in water.

See the FAQ here titled How to grow and avocado from seed. Click blue FAQ button top of the forum page.

Dave

I used to root my avocado seeds in water, but eventually just started sticking them about 3/4ths their length into the dirt with my houseplants. After that, the only care they get is the same care I give my houseplants...normal water, normal food, etc. In time, they sprout and grow of their own accord, and I find the plants to be much stronger and healthier than those I've sprouted in water.

I planted almost every seed from the avocados we ate last year and almost every one of them came up. I lost maybe four or five to my chickens, and approximately seven or eight to winter kill, but I only have limited room to overwinter my plants in my house, so I chose the two best looking plants to bring inside. Btw, all the plants survived quite well down to about 40 degrees on a regular basis, but hard frosts killed the exposed ones in my yard and the THIRD hard freeze finally got the one on the porch.

This gives me hope I can successfully overwinter these plants on an enclosed, barely heated porch in the future and not have to bring them into the house, as I'm pretty sure they'll do quite well if I can keep the room somewhere in the range of 40 to 45 degrees during the coldest months of the year here, which are generally January and February.

Currently, one of the plants has been growing for a little over a year now, and I've actively worked to dwarf it, so I can keep it in as small a container as possible for as long as possible. It stands a little over two feet tall right now and is putting out a new flush of leaves at the top. I noticed last summer that it had formed a ball-shaped leaf crown that was quite pretty.

The growth slowed when I brought it back inside for the winter and I stopped watering until I saw the leaves begin to severely droop, then I started watering again on a limited basis. Shortly after I resumed watering, the crown/tip of the plant grew about two inches and began forming new leaves; my plan is to continue to supply only the amount of water needed to support and encourage leaf growth, but not enough to encourage new growth in height.

I intentionally dwarfed this plant just to see if I could do it, and it's responded extremely well. I'm happy about this, because I've had several failures in the past, and discovered the stems have a tendency to become quite leggy very quickly if they don't have enough light early on in their growth. I just got very lucky with this one...:D.

Only three days ago I discovered a new and very 'leggy' avocado seedling sprouting from one of my houseplant pots and I did't even know it was there until it literally hit me in the face as I was watering! By the time I can put it outside, the stem will likely be so thin and wobbly it can't hold its leaves, but I might try staking it.

Good luck with your seedling!

Blue