Here at Polly’s Nursery, we get quite a few questions, some from frustrated gardeners asking: “Why their blue Hydrangea won’t stay blue?!” We would like to tell you: “They are just too happy in your garden to stay blue.” However, we have done our homework and are here to tell you the real reason it is difficult to keep hydrangeas blue here in Northern Michigan.
When you first saw that blue hydrangea, it was in a pot and had most likely lived it’s entire life in a pot…it’s safe little pot-world where it’s blue-ness was easily maintained. What I’m speaking of is the chemistry of the soil in the pot and while it is easier to keep a hydrangea blue in a container, it doesn’t make for the happiest of plants. The thing that makes certain hydrangeas blue is aluminum and for the plant to be able to take up the aluminum, the soil has to be slightly acidic. The plant chemistry is even more tedious but the primary reason it is difficult to maintain the blue color in hydrangeas once planted in the ground is that much of Michigan is covered, geologically, in limestone. The limestone buffers the soil’s acidity and keeps it neutral to slightly alkaline. This causes blue hydrangeas to turn pink over time. Yes, it is possible to maintain the blue color by adding Aluminum Sulfate (which tends to lower the pH of the soil) but we caution you to be very careful when doing this as you can easily overdo it possibly burn the plant(s). Additionally, lowering the pH of the soil may be detrimental to surrounding plants so you have to be careful in your fertilizer application. This is one of the main reasons we tend not to carry blue hydrangea varieties at the garden center. Our suggestion is to be happy with the color that your hydrangea wants to be, there are more frustrating gardening issues to be had. Also, be advised that you cannot turn a white hydrangea blue (or pink.) Varieties like Incrediball, Annabelle & Pee Gee will always be white.
We have included a few links here with suggestions on keeping or turning your hydrangea blue.
- Here’s one on Pruning & Maintaining your Hydrangeas: http://www.taunton.com/finegardening/how-to/articles/how-to-prune-hydrangeas.aspx
- More about Hydrangeas: http://www.usna.usda.gov/Gardens/faqs/hydrangeafaq2.html