It is also the nature of this tree species to drop older leaves after they yellow, as they are pushing new growth this time of year. If the newest tip growth is not wilted, and they yellowing of foliage is only the older, lower leaves, it is probably adjusting to your site. It may have seen less sun at the nursery, so is under more moisture stress now that it is planted out, and presumably getting more sun. The critical thing with Arbutus 'Marina' is to make sure you gave it excellent drainage, and that it is not sitting in water at the base of the root ball. You should probably also use the hose once a week to give it a good slow soak to thoroughly wet the entire root ball, as conventional spray irrigation run times aren't going to be long enough to wet the soil down to the 2 foot depth of the root ball. It is a beautiful tree, and much easier to grow than the true native Arbutus menziesii, I hope yours recover.

Zone 9 where? Really, the Sunset zone would provide a much clearer picture of your conditions. I live in Zone 9/Sunset 23. Clay soil can be a problem with Arbutus Marina. The lack of drainage makes them even more susceptible to Phytophthora. Even with good drainage, Phytophthora can be a heart breaker with these lovely plants. I have lost three growing in huge pots; one tree, in the ground (sandy soil), remains healthy (knock on wood). Arctostaphylos prefers sandy/rocky soils. Emerald Carpet also prefers acid soils. I haven't tried Emerald Carpet, but in my area (south Orange County CA), A. edmundsii ('Little Sur') and A. uva-ursi 'Point Reyes' are thriving in very bright shade/protected sun. The former beside a shed, and the 'Point Reyes' under Iceberg rose bushes. Not sure they would be thriving in full sun here. These are being irrigated with drip. Howards have not been easy in our garden. We have lost three out of four of the 1 gal. plants tried. But our watering system is drip, and these guys are known to hate drip. How are you planning to irrigate?

Thanks... I'll keep my optimism and hope for the best for my Arbutus marina. I've picked a spot in full sun (of course) with good drainage, etc etc. I've given up on the native Arbutus (at least temporarily). I've tried several times and have had limited success, though I've never had one die due to harsh winters. They always seem to die in late spring / summer / fall, for no apparent reason (which the native Arbutus is known for). The last one I had lasted for 4 years. It was a nice looking, healthy little tree and then, poof, it just decided to die in mid-July. I hope you have more success than I with that that one. I am (probably temporarily) content with looking at the huge healthy native Arbutus across the street in my neighbour's yard.

In Europe one sees old Arbutus that have outgrown, seemingly, various insults to their trunk and bark. In a climate that keeps them happy they are pretty darn tough plants. (actually, come to think of it, I saw this in West Texas, too) So you are probably best just taking a wait and see approach, but we will see what Sara M. says...