This tree needs to be outside where it can get the normal temperature fluctuations of the real world. Bonsai are outdoor plants and will die if kept indoors for long periods of time. Your tree is probably going into shock and reacting by going prematurely into dormancy. Elms are very forgiving and resilient. It will probably recover if you put it in a place where it gets morning sun and afternoon shade and keep it moist but not soaking wet.

Well ! There are many so called Chinese Elms. Many are Zelkova species. However I have been caring for these since 1972. That was when I was told it was an inside tree. It does not like overwintering inside : it gets dried out for one. This tree likes light as do most Bonsai , and plenty of it. I always keep these trees as normal outside trees, over wintering outside with a small bubble wrap cover. They need to lose their leaves just like any other broadleaf tree. Since I used this approach , I have never lost one. All my bonsai get a daily watering or two in a hot summer. Best is one early morning and another late afternoon. The Chinese Elm is just the same and loves this. I live in England near Warwick Castle. I prune these trees quite often and feed with Bio Gold solid blocks--2-3 each. This is a natural feed and you should never lose these to over feeding. These trees also need Oxygen for their roots so a fairly loose soil based on Akadama and Lava with a little compost and bark flakes.. Hydrogen Peroxide is excellent to improve Oxygenation is your soil is too soggy (repot ). You will need to dilute 3% HO2O as it can burn your roots if too strong mixture is used. I use a table spoon per 1/2 pint jug.. Most deciduous trees are hardy in my climate. So don't overdo the cocooning during winter.....during this time they don't need light at all , but should be kept just moist and no feed !!! or you will encourage growth during the winter , not what you want. So good luck . I hope this helps.

I wouldn't panic yet! :-) Both my Asian (a Chinese one and a Japanese one) are still dormant. Their buds should start swelling in the next week or so if the weather warms up a bit. Mine booms on 'old wood' whereas yours will bloom on new growth. May is always an anxious month here - first waiting to see how many flowerbuds survived the winter, and then, once the flowers start developing in mid-May, keeping our fingers crossed for no late frosts! All yours needs to do is have some foliage buds survive to produce new growth this spring. Since I've not grown one of the native kinds, I don't know exactly when they start to 'wake up', but I think it's too early to be overly worried yet. Hopefully someone with local experience with 'Blue Moon' can give a more definitive answer.

Ok...due to the timing and the appearance, that looked like winter kill, but in your climate that's not an explanation. The only other things I can conclude are: 1) the plants were not in good shape when you got them, although they might have looked ok, or 2) that they got dried out at some point. I have to say, though, that this is weird; bamboo are pretty tolerant of water conditions (though it's hard to over water them). You also sound conscientious. Is it possible that they didn't get watered for a one to two week period when it was really hot and the ground got dry?