I've observed that phenomenon on native trees. TN is subject to summer droughts. After a long hot, dry spell a good thunderstorm will drop a bunch of rain, and the trees that like moisture, tulip poplars, birches, red and silver maples, cottonwoods etc will drop a bunch of leaves over night, some almost completely defoliate. Excessive dryness causes the defoliation, I think the rain just hastens what would have happened in time. Surely there's a scientific reason for this, I've never looked into it though.

I have two in full sun that defoliate every summer when the heat and dryness get too much for them. They are therefore not particularly attractive. I love the tree, however, so a few years ago I planted three b&b in part shade (also less windy site) and put more irrigation on them. They are doing great. I am going to take out the original two when I get enough energy. I grew them up from 4" so I'm sentimenral about them, but they really look awful and I don't get that wonderful sugary smell in the fall. I think your problem is drought; that is what would cause the tree to dump leaves that had gone from being assets to liabilities. The watering may have hastened the final formation of the abscission layer that was already well underway. In any case, watering was almost certainly the right thing to do. They are Asian and are accustomed to heat and humidity and will be fine with enough water. Great trees - there is also a lovely weeping cultivar and also one with maroon leaves ('Red Fox').

if i work under my presumption.. that trees do things in slow motion ... which is never defined by the word DAYS ..

then i might suggest it was coincidence ...

ken

After the first couple yrs of needing alot of water, my 20' Katsura
seems unaffected by heat/dryness, but prb'ly because it's near a stream.

What ken says above, dropping leaves after a big rain, makes sense as dropping leaves is hastened by growing over the leaf attachment to "push" it off -- like in autumn. A good rain & that growth to push failed leaves off occurs quickly.

I wonderedI about rain hastening this tree's "normal" response to drought, but didn't think it through 'biologically'. I planted this as a future replacement tree for a huge maple that will someday die. I if stay here until I die (within the next 20 years under normal circumstances) and the maple and katsura can wait for me to kick the bucket, I'll be a happy old person. Then someone can put me in said bucket and sprinkle me around some plants that like bone meal, or would it be calcium? What is left in our bones after cremation, anyway?

yeah.. i didnt get the pouring part of the story.. and cant picture in my mind.. hoiking 15 gals of water around the yard ...

ken

5 gallon bucket at tree. Hose end at tree. Fill bucket 3/4 full b/c it gets away from me of its nearly full. Pour slow so stays at roots instead of going downhill.

now ask why I didn't just left hose to trickle for seversl hours.

Because I had other neglected plants and a prediction for 2 more days in the 90s

I water each shrub of mine 75 gallons of water. My hose gets 5 gallons per minute and each shrub gets 15 minutes.

15 gallons for a mature tree? That's puny, in my opinion. It dropped its leaves because it wasn't getting enough water, and your 15 gallons was, unfortunately, too little too late. Good luck.

why not drill a small hole in the bucket .... i dont know.. 1/16 of an inch ... carry empty to plant .... fill with water from hose.. water everything around it.. while it weeps out ...

someone has to do this ... would know hole size ... ken

Back in 2012 I had a rude awakening concerning the amount of water soil needed to support trees. We had our record (since the dustbowl) hot and dry summer. Since I had moved in about 02' I had planted small trees and given them a gallon or two of water to get them established.

Off and on in between I had watered the grass. Now I have an acre + so I don't do it regular like. I drag 3 hoses out with sprinklers between them and at the end, crank them on and come back aj hour or two later and do the other side maybe once a week.

THAT WAS NOT ENOUGH IN 2012.

My small trees were now 20 foot plus and I discovered I had to drag out the hose/sprinkler assembly when I got home from work and leave it on until midnight or so when I was done with the model railroad.

The next night I'd do the other side and on the 3rd I'd rest for the better part of two months.

In a pot 15 gallons of water is a lot. In a dry yard it gets sucked up by other things like grass or it seeps away into the dry surrounding soil.

Too little, but not too late with certainty. I won't accuse myself of arborcide until I see for myself the tree has not leafed out by next mid summer. Yeah, I know it wasn't enough but the dropping its leaves wasn't a personal criticism of my watering technique.

A very generous neighbor has allowed me to use his well water (its only for irrigation) when his system isn't on between 8 and noon. I put on the sprinkler (not a little whirly gig but a rotating one) for at least 8 hours or more and check the soil afterwards. It has been soaked. Then I try and mulch....but sometimes I just can't get to it. It is getting difficult to push a wheelbarrow even 3/4 full of mulch. But half full just means more trips.

Then n I have to let go of it. The garden is a gift and a preoccupation and it's bad enough I go to bed trying to figure out a design or plant problem. At 67, with a stroke prone spouse and half the income we had 2 years ago all I can do try my best.

BTW anything I know about watering, I learned from Ken. Also, trying not to "sweat the small stuff."

Katsura is pretty intolerant of drought, hailing from a part of Asia that has much more reliable summer monsoons than what the semi-reliable Eastern US summer rainfall, which looks good on paper but we know how variable it really is!

That said,, 15 gals on a 20' tree is like you or me drinking 1/8 cup of water after working out for 2 hours.

Instead, use a lawn sprinker or soaker hose and calculate the equivalent of giving the entire rootzone as much water as a 2" rainfall or more.

And do it three weeks ago. ;)

yup

Agreed on the soaker. My water comes from the Mississippi. If you are draining a well go soaker, especially if you are just trying to hit 1 tree.

Not draining the well. On town h20. Well is only for irrigating lawn and garden.Waiting for some soaker system parts and cooler days to rejuvenate soaker system which is far more effective, I know. Not so easy climbing around the hillside and under trees and shrubs as it used to be. Have a heart, people!

When I said too little too late, I was referring to the leaves for this particular season, not to the life of the tree as a whole. That remains to be seen. I am always amazed at how people expect a living thing that requires water, just as we do to stay alive, to expect it to survive on a pittance of water in these hot, rain-less days (weeks). I can't believe your neighbor is sharing his precious well water with you. Yes, it is absolutely generous, and it is honorable on his part, but if you are experiencing drought, he is putting his precious aquifer at risk. I wouldn't do it. My next door neighbor's well went dry last year. Mine didn't, but I am cognizant to the risks of watering my plants as much as I have, and it's only been twice a week, during these 80-90 degree weeks of no rain. I wonder every day if I'm prioritizing my plants to the detriment of my aquifer. By the way, we do have hearts on here. I have no doubt that walking the hillside is no fun at your age, its no fun at my age and I'm younger than you. lol I'm sure with your husband you have your hands full. We're just trying to help you keep your plants alive, for you and your husband.

I'm fine now. "I love my trees too" and my age has little to do with watering. I just let my garden get too big and whine about the labor it requires, on occasion. At least I don't give a cr-p about our little lawn. It can die if it wants to.

Marie

Marie, hopefully that Katsura will be OK. I cut mine down not too long ago. I think from the beginning it was diseased. Never did well and was all black inside when we cut it down. How are all of your other many trees doing with the drought? Hopefully you got a little rain with the storms that came through this evening.

Toronado, my DH is on the same schedule as you! Set up sprinklers, work on model railroad til all hours, turn off sprinklers!

Ilovemytrees, I worry about same with our well. We are blessed with a great well, but I always wonder if we are stressing it out, and I'm always amazed our well pump doesn't crap out with all the watering we do.