Answer: These shrubs do well in average soil that is well drained and so would not really need much fertilizer or watering (except in times of drought). You could top dress with a good quality compost in spring and then use several inches of organic mulch in a flat layer over the root area year round. This should be adequate to keep them happy. In addition to the possible causes you listed, red color can be reduced if the plants are overwatered and/or overfertilized late in the season. This can cause them to stay in active growth too late into the season so they do not begin to slow and prepare for winter dormancy in the normal way. Late pruning can also stimulate tender new late season growth and prevent them from slowing down and turning color. Or, if the weather is not cooperative in that the days need to be mild and the nights cool but still above freezing. Drought can also cause the leaves to turn brown and fall off rather than color to a nice red. The named varieties sold by Monrovia are vegetatively propagated, not from seed, so that should not be the cause of the problem. I hope this helps you trouble shoot.
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