Q.lemon trees
How large should starter trees stay in a pot before going in the ground and what time of year in zone 8 is good? Thanks

The optimum time of year is late winter to early spring.
You can plant your tree nearly any time, but you will need to take some extra precautions.
Planting in summer can done, but you just need to make sure you water regularly and do not let the soil and roots dry out.
Newly planted trees have little defense against heat and dry winds, so you will need to carefully monitor the trees.
You can leave the tree in the pot with the same attention to water and weather conditions and wait for a drop in temperatures to plant.
https://www.gardeningknowhow.com/edible/fruits/lemons/how-to-grow-a-lemon-tree.htm