Q: Earlier this summer I planted three butterfly bushes in my full sun front yard. One looked great after planting but is now all brown and dry. Would it be too late to try to plant a new one?
A: I have been inundated with questions like yours: quick decline and death of trees and shrubs that were planted this past spring. My bet is that in almost all cases the cause of the problem is simply lack of water to the root ball. Spring-planted woody plants are MUCH more prone to problems than those planted in fall. When a plant is installed in spring, warm weather stimulates immediate twig and foliage growth. Not much energy is directed toward root growth.
The root systems of your plants are almost the exact same size now as it as when it went into the ground. If a plant is watered weekly between spring and fall it can usually hang on and survive. But if the soil dries and you fail to water a couple of times, the root system begins to fail, leading to death in August and September.
Return the dead plant and plant another in late September, when the soil is warm but the air temperatures are a bit cooler. In the future, make it a rule to plant woody plants in fall or early winter.