Good drainage is key, especially in cool wet spring weather. I have very sandy soil, so I just add lots of compost every year, and call it good.

Yeah we have been getting a ton of rain, most of the plants love it but not sure how the dahlias will do. What could I add to make sure drainage stays good...sand or perlite or something?

Either on will help, sand will last longer. Pearlite is great for containers, but it will break down after a year or so in the ground.

Great thanks!