Try switching to aperature priority and closing it up as much as possible (highest f number you can ), that will increase DoF and you can reduce it if you want to as you get used to how it works. Flowers arent really going to move that far or run away so you can wait for a bit of calm air.
That would be lowest number. The bigger the number the smaller the size of the aperture/diaphragm /iris
f1 = O
f2 = o
f22= .
etcat f1.4 OF is easyto mesure in MM, at F22 you would be better of with miles
DOF isnt just aperture