They're beautiful, and seem to have put out a lot of new growth. I wonder how well they tolerate your dry summers though.
I had a 'Briotti' die on me the first summer. I'm now trying A. pavia.

Thanks for sharing!

Thanks Jnarvaez. I have to water a lot. These like more water than I thought they would, but they're babies, only in ground 2 years 5 months, so hopefully when they get older and a better established root system they'll not need so much watering. They are lined up about 1' from a creeklet so when their roots find that they should be happier.

This spring they are finally growing visibly! No picture can capture the richness of their blossoms and how much the hummingbirds love these trees.

Beautiful! You are obviously keeping those hummers happy.

Thanks Esh! Some hummers have taken up residence in the yard. They live in a Sunset maple that's got a lot of die-back from transplant damage (too big a tree to try to move). Last year they stayed until Autumn. They whizz right by my head and click clack and want to hover in the mist above the hose while I water. This year we have 2 different kinds of hummingbirds. They made a tiny nest in one of the gingko trees. The horsechestnuts are now making their spikey balls but the honeysuckle has begun blooming ...

The candles are for the most part gone now ... wish they lasted 6 months! :-)

The spikey balls that house the chestnuts are now forming.

Does anybody know how old these trees have to be before the balls stay on to maturity? Mine fell off the last 2 years very soon after beginning to form. The tree wasn't strong enough to support their weight apparently.

LOTS of balls forming, looking cool & ornamental, wondering how many years it takes for the tree to be able to keep them.

Usually it's a case of pollination. If the flowers were pollinated by another suitable Aesuculus tree, then the fruit develop to maturity. But if the flowers either weren't pollinated, or were unsuccessfully pollinated by an incompatible Aesculus, then the fruit would either initially look like they are developing only to drop off soon afterwards. This happens a lot with Magnolias and Oaks. They will hold on to their fruit, and the fruit will even look to be developing, but then sometime before maturation, they will drop the developing fruit(Magnolias do this 4 to 6 weeks after flowering and Oaks will do this as long as 3 or 4 months after flowering) because the flower wasn't properly pollinated. I suspect that since you have all the same cultivar they are probably not self compatible enough to properly pollinate their own flowers and hence the fruit are dropped. Since they are all the same cultivar, they are all genetically identical, so any pollen landing on any flower would be the same as if the pollen from one lone tree landed on it's own flowers. Plant another variety of Red Horsechestnut (Aesculus x carnea), like 'Briotii or 'O'neill', or perhaps even one of it's parents(A. hippocastanum or A. pavia) and you should get some fruit, although some claim at least some Red Horsechestnuts are sterile.

Thank you Kman! That is an explanation I would never have thought of. I was afraid I was over or underwatering them, or they were just too young.

I have nowhere to plant a hippocastanum but if something expires that's what I'll do -- really love the huge trees. Thank you so much for explaining this!

I think from all the photos of yours I see, they look quite healthy and happy.

I just checked my notes and an informal arboretum I visit from time to time has a nice A. x carnea 'Briotii' and no other Red Horsechestnuts, but they do have a couple European Horsechestnut(A. hippocastanum) and their 'Briotii' has a decent crop of Horsechestnuts each year I've visited in fall. Maybe you can convince a neighbor to plant one? or maybe even squeeze in the much smaller growing A. pavia and see if it does the job? With Horsechestnuts or without, yours look really nice!