Blue Hydrangea That Has Bloomed Blue But Quickly Turned Brown.

Question

I have had this hydrangea for many years and its blooms have kept their color for several weeks, if not longer though the color fades with time. This year they bloomed blue but within a week the blooms faded to a beige/brown. There is a white hydrangea right next to it that is fine. What could be wrong

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Answer 1

Hydrangea macrophyllas and serratas produce blooms that go through a series of color changes that end in brown. When the bloom prematurely turns brown, the plant may be getting too much heat stress during the summer months. Heat stress can take one of the following forms/scenarios: very high temperatures, summer drying winds, low humidity, lack of water (or insufficient water), too much sunlight.

In the wild, these plant are normally understory plants so provide shade starting around 10-11am.

Instead of watering based on a schedule, water the soil as soon as the soil feels dry to a depth of 4” (4” tends to be the typical depth of most hydrangea roots).

You should provide enough water to reach all the way down to 8”. So water the soil when appropriate per the finger method (meaning when it feels dry at a depth of 4”), wait for the water to drain and insert a finger into the soil to a depth of 8” (try several spots around the shrub); if the soil feels dry then either you missed a spot, the soil is not draining well or you did not use enough water.

Maintain about 2-4” of organic mulch (no rock mulch) throughout the whole year.

Note: there is a way to get brown blooms if the plant gets a fungal infection called 'grey mold' too so avoid watering the blooms (and the leaves); instead, only water the soil… as best as you can. If using a sprinkler irrigation system, set the station to water around 6-8am instead of spending the night with wet blooms. That should minimize the chances of getting fungal diseases.