u/PiecesOfRing

The first pic is of my oldest (2 years in the ground) Coast Redwood, as part of my grove which includes more smaller Redwoods, Giant Sequoia, Deodar Cedar, Radiata Pine, Swamp Cypress, and Incense Cedars.

I'm about 45 minutes SE of Brisbane City, Australia.

They seem to be surprisingly happy here as long as they get water during dry spells, as the sandy soil on my property tends to desiccate real fast!

The next pictures are of a large, local 40 year old specimen, but this one is at about 1,500ft higher despite being 15 minutes away. The climate is much more suitable up there than down here, so I'd expect mine to grow much slower.

Our climate is more similar to the SE USA than their native Cali, with hot, wet summers and dry, frosty winters. Rainfall can be unreliable some years, so I have to keep them watered until they establish.

There are many Redwoods in Australia, but existing groves and individuals are entirely limited to the cooler and wetter southern states. These are quite experimental up here, with mine being the only known low elevation elevation specimens in my giant state.

This one seems to be establishing well, with the trunk girth and canopy width tripling since planting.

I have (or had) 4 Giant Sequoias on my property (Tamborine, QLD, Australia). It's a bit of a zone push, but nothing crazy here. It neither gets too hot or too cold in an average year, with the temperature range on an average year being 38c on the hottest day and -3c on the coldest night (extremes outside of this range can happen though). The rainfall is normally heavily summer-autumn biased. They've been here for about a year.

One of them died in summer after an unusually dry hot spell, and it looked like something had dug the soil away on one side, exposing the roots to the hot sun. The one in these pics was fine the whole time.

Things are cooling down now heading into our winter, and we've had quite a lot of rain, but we did have a dry spell (but not very hot), during which the lower branches on this one started to brown despite weekly waterings. They are all in sandy soil on a slope, so there's no chance of over watering, but more drying to fast.

Even during this cool, wet period, the lower branches seem to keep declining further upwards, and this is how the first one started to decline before total death.

Any ideas what could be causing this, and how to hopefully remedy it? Even if this one dies, I could at least use any pointers to prevent the same for the other two.

I'll add that I also have a few Coast Redwoods that have been in the same area for a few years now, and they are much more sensitive to drought and heat, so I thought the Giant Sequoias would be a lot easier!

Thanks!