What if they try to help but only end up making a mess?

Okay, I love my hubby and son to death. Really, I do, but sometimes I just want to say, "Please, I can do it myself."

This afternoon I went outside to trim the bushes. I told my husband that it wouldn't take long. He asked if he could help and I said, "No, it's okay. I'll do it."

Well, after I trimmed 3 of our bushes, here he comes to help. Oh boy. I repeat that it's not necessary. I can do it and it won't take very long. He INSISTS that he's going to help. Off he goes to the front yard.

It takes me about 10 more minutes to finish trimming all the bushes in the backyard. I go to the side of the house where I see ALL my flowers have been chopped down. UGH!!!

 I go to the front to see what he is doing and inform him that the flowers he just chopped down were not weeds. I ask him to only trim bushes and that I really could finish it myself. He replied, "Oh, I'm sorry. They looked like weeds to me. I'll just finish these bushes for you."

I continue to trim the bushes in the front of the house. I am working my way toward him. I have electric hedge trimmers and I am just trimming away. All of a sudden, I can't get them to work. Hmmm... that's really odd. I ask him to come take a look.

"Uh oh," he said. He brings me the extension cord that he had just chopped in two. This is not the first time he has done this. I inform him that is our last extension cord. I reiterate that I can finish trimming the bushes and he can go inside. He finally does, mumbling that he will fix the extension cord on his way.

I complete trimming the bushes, UNTIL I reach the other side of the house. I wanted to cry. My beautiful crepe myrtle had been hacked down to the roots. It was a good 6 foot tall crepe myrtle. AHHHHHHH!!!!!!!

I went inside and informed him of what he had done and why I didn't want him to help me. He said he'd buy me another one. I don't want another one. This is not the first time he has done this. I plant bushes or flowers and they either get run over by the lawnmower or chopped down by the weedeater. I've given up.

So, do you let them go ahead and help KNOWING of the mess they are going to make? OR do you insist that you do it yourself?