Q.Tipuana tipu trees
During the second week in February we planted a dozen trees both bare root and potted, from pear and citrus to oak and jacaranda. All are doing well except the two Tipuana tipu trees from 15 gallon potted stock, about 7 ft tall. We live on 3 acres in inland north San Diego county (35 mi from the coast), previously planted with avocado. Both trees are in different locations on the property, in full sun, elevation about 2000′. Since planting, temps have ranged from lower 40’s to mid 80’s. We’ve had multiple-day torrential rainstorms with some high winds, interspersed with sunny and warm. The trees are well staked, the soil pH 6.0 and well drained. We took care of the gophers prior to planting. The leaves are turning dry and crispy and falling off. We bought all of the trees from a nursery that is 20 miles closer to the coast, where the temps were in the 50’s and 60’s. (1) Did it get too much or too little water? (We only watered well at time of planting then let the rain do the rest–10-12″ the past two months). (2) Did transporting them to our house stimulate a winter dormancy? (3) What did we do wrong? Photos: Tipuana #1 barely any leaves left. You can see healthy young jacaranda in distance to the right, planted at same time. Tipuana #2 leaves all yellow. Pine tree in distance is >25 ft away. Thank you so much!
I found some planting tips that I will mention, though you have listed a through explanation of planting.
Planting hole should be dug twice as wide as the container, but not deep
Heavy or clay and sandy soils should be amended with organic material.
https://www.gardeningknowhow.com/special/organic/the-importance-of-soil-for-an-organic-garden.htm
Keep the root ball intact when removing form the nursery pots. Roots do not like to be disturbed, but gently uncover the bottom root surface.
Plant level with the surface and spread out the bottom roots.
Fill around the roots with amended native soil.
Cover the area, except the 6 inches around the trunk with 1 of 3 inches of hardwood mulch.
Water deeply and slowly.
Stake the tree as they are sensitive to wind.
Allow the top few inches of soil to dry before watering again.
In the first few weeks to a month, water 2 to 3 times per week with a soaker hose.
A regular dose of all purpose fertilizer during it's growing period, ( do not fertilizer during dormancy)
My research show that the tree prefers highly acidic to slightly alkaline ph.
Yellowing of leaves is generally a watering issue. Either the tree is not taking up the water, not being watered enough or it is excessive water, and the soil is not draining.
A tree can also be stressed from transport and change in light conditions, temperatures, and humidity levels.
Loss of leaves is not uncommon from planting stress.
With all that said, one can do everything correct and still lose a new planting. Often times you just can't explain it either.
I would inform the garden center that you purchased from of the issues. Most reputable business will guarantee a new tree for the first year.