Question
I have several annual flower beds and all do fine except one. For the past few years any annuals I have planted there have slowly died. It starts with one plant and then moves on to others. I know there is not a problem with the plants themselves as I have plants from the same flats at other places in my yard. I have tried vinca, petunias, and this year, verbena. Thank you for any help you may be able to give.

Answer
Hi Jaye, If it's toxins (herbicides, etc) only a soil analysis will confirm that, but usually it's fungal and since it's one bed, probably there is a drainage issue also.
Start by checking your pH just to see if it's out of range.  For the plants you mentioned, it should be 6 - 6.5.
Second, treat the area with a good soil fungicide, see your local garden center for their recommendations.
Then plant a few annuals and add enough soil amendment to raise the plants slightly above your existing ground level.
I'd only plant a few until we see the results.  I'd try something like verbena and something woody like lantana.
Use caution not to over-water and see if that solves your problem. If not, I'd have the soil sent to a lab to either identify the problem or rule out toxins and then focus on building a healthy, well drained bed.  Jim