Immature blooms sometimes appear greenish or whiteish. They should change to their normal colors in a week or so.

Luis,

Thank you for responding. Here is a picture of my Merritt's Supreme after waiting 2 weeks. The blooms remained white. Any suggestions?

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As a newbie, any help is appreciated. :)

Hello snsn. Your green blooms are immature blooms who will change color after a while (weeks). The other ones are blooms that suggest your roots are in transition from "only growing in the hydrangea's potting mix" to also growing in your garden soil.

When your shrub originally bloomed pink, that was caused by the soil potting mix having alkaline soil and-or little to no aluminum.

This year, the roots have expanded into your garden soil and are able to get some aluminum so they are no longer pink. The blooms are now transitioning into the more neutral-to-acidic environment of your soil.

They will temporarily look white or white with "a dusting" of blue (like the rightmost bloom in your picture). As the roots grow even more into your garden soil, they will absorb more aluminum and nutrients from your soil; the blooms will turn a darker shade of blue. When the roots get most of the nutrients from your soil, the colors will then stabilize... meaning they will bypass "white" and go directly from green to a shade of blue. This is a normal process and takes 1-2 years from the planting date. So, no need to panic.

Luis

PS - I am not sure why the blooms' sepals are having so much browning though. One way that can happen is if the shrub is exposed to too much sun... not enough to trigger leaf scorch but enough to trigger browning of the blooms. Another way that can happen is if they are getting too wet and developing fungal infections; in that case, you may want to water only the soil and do it early in the mornings. Lastly, periods of dry soil followed by periods of moist soil could also cause that look since blooms are the first thing that the shrub aborts when it has insufficient soil moisture.