Fruitless pear tree, one large root is coming up so there is space between it and the ground. What's wrong?

Question

We are in CA and haven't been watering deeply is that the cause?

Answer 1

Sounds like the tree is starting to tip?  I'd water deeply (that's especially important for trees!), do some pruning to remove mass on the downhill side, and cable the three back upright.

This is assuming the tree is under about 15 ft tall.

On a taller tree, tipping is a real death sentence... you can't trust it will ever be stable in a wind.

Answer 2

It could be a flowering ornamental pear (pyrus) or it is just lack of water.  Fruit trees like regular watering and regular fertilizing.  As the root is comming out of the ground I would say it is not being watered or only watered lightly.  Start a regular watering schedule say once a week and water with the hose turned on about 1/2 for about 1/2 and hour.  Water on the ground on the edge of the tree, this is where the roots are feeding.  Once the tree starts to respond use a suitable tree fertillizer.