Answer: There should not be such a significant difference between, them although in my experience the white does tend to be the more vigorous. If you started them from seed, you might find that there is a difference in the soil in which they are planted. If you started them from purchased transplants, you might find that the white ones have rooted better than the darker ones. This can happen for a variety of reasons but usually relate back to stress of some sort. For example, they could have been severely rootbound prior to planting or they could have been allowed to dry out severely prior to purchase. Another possibility is that the grower had added some long release fertilizer to the white ones and not to the purple ones. Sometimes, too, there just is no real explanation, it " just happens. " Such are the mysteries of gardening!
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