Home » Plants & Animals » Gardening in B.C. » Hydrangea Q And A

Hydrangea Q And A

© Susan Ward

Hydrangeas are one of the reasons that gardens in Southern B.C. elicit so many oohs and aahs in summer. There's something surreal about their gigantic, brilliant blooms and the density of their vibrant green foliage. Perhaps it's the way the low summer sun sets some of them aglow, or maybe it's that so many of them have blooms that are so strikingly, truly blue - a blue that we're not used to seeing on a real live shrub. Whatever the reason, hydrangeas are one of the treasures of the B.C. garden. So this week, here are the answers to the questions I'm most frequently asked about this perennial favourite.

Q: How come my hydrangea isn't blue?

A: Your hydrangea's color is determined by its type and by the availability of aluminum ions in the soil. For instance, Hydrangea macrophylla 'Hamburg' will bear large mophead flowers that are colored dark pink ( if your soil's pH is higher than 5.5) or dark blue (if your soil's pH is lower than 5.5).

So if you want your hydrangea to produce "bluer" flowers, you should increase the acidity of your soil by adding aluminum sulfate, iron sulfate, or sulphur. (It also helps to use the faded flower heads as a mulch under the hydrangea, because the faded flower heads have a high level of aluminum.)

If you want your hydrangea to produce "pinker" flowers, you can raise the pH level of the soil by liming around the hydrangea.

Whichever way you go, the process of sweetening or souring your soil will take several months. And it will be pointless if your hydrangea is white to begin with; white varieties will stay white, no matter what you do.

Q: Can I plant my hydrangea in the sun?

A: Yes, but it's not recommended to plant a hydrangea in full, relentless sun. Most hydrangeas do best in partial shade, although they will tolerate a sunnier spot, once established, as long as they get plenty of water. You may notice, however, that the leaves actually "sunburn", and that the flowers don't last as long.

Q: When should I prune my hydrangea?

A: I recommend waiting until spring, so you can see the buds swelling. If you prune your hydrangea right after flowering in the fall, you run the risk of cutting off your potential flowers for next year as hydrangeas flower on the previous year's shoots. So wait until spring, and then lightly trim each stem you prune back to a pair of fat, swollen buds. (It's the fat buds that produce the flowers.) You should also remove any damaged or dead shoots when you prune your hydrangea.

The copyright of the article Hydrangea Q And A in Gardening in B.C. is owned by . Permission to republish Hydrangea Q And A in print or online must be granted by the author in writing.