Answer: Verbena usually does well in hot sunny weather. As with most annuals, it needs a soil that is evenly moist but not sopping wet. Soil preparation would ideally include the addition of ample amounts of organic matter such as compost along with a bit of sand if your soil is a heavy or clay type of soil. Next, transplants would be acclimated from the greenhouse to the outdoors gradually to condition them to withstand the rigors of life in the garden and minimize the chance of transplant shock. In addition, the transplants would be set out when the soil and weather have warmed and all danger of frost is gone. Setting them out too early or without conditioning can cause them to be stunted. Another possible reason would be that they have failed to root into the surrounding soil which can happen if they are severely rootbound prior to planting or if the soil is poorly prepared. One more possible reason for poor performance is that something happened to them before you bought them so that they were severely stressed -- and are either stunted as a result or simply sulking. At this point you could replace them with something else or try to kick them into growth. Make sure you are not over or underwatering, continue to deadhead and make sure the fertility level is good. You might try using a fertilizer formulated for blooming annuals and/or a top dressing of compost and possibly even a seaweed based fertilizer. Lastly, make sure you are not oversupplying the nitrogen as this can cause foliar growth and reduced blooming. I hope this helps you trouble shoot your plants. Verbena is lovely when it is behaving the way it should!
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