Why do elm buds wither?

Tell everyone a good news. This morning, I found that some branches have sprouted, including the thickest top branch this year. Thank you for your suggestions, especially friends at hz. 1000. Here, I want to tell you how I handled it, especially thanks to my friend hz. 1000, because he was right about the cause of my elm bud withering. When I get home, I loosen the topsoil first, then water it in the basin (it may take a long time, 30 minutes), and then put it in front of the window sill, so I can get the sun, but I won't be exposed directly as before (there is a flower stand outside the window sill, and the big dog has been placed on it all day, so the sun can be exposed directly after 3 pm, because the window is southeast), and I have been treated with pesticides. It's been 1 week since I posted today. I'm glad to see new shoots again. To sum up the experience, it seems that although this elm is not afraid of heat and sun, it is still far from pomegranate (my pomegranate has never bloomed, but it has been exposed to the sun since summer, but it has blossomed and borne fruit), and it will still be shaded in the dog days. The root is not rotten, which means that watering is still right. The soil is slightly white and watered thoroughly. There is no pot now. After the pot is put on, be sure to water it by soaking.