Homing in on the ideal environment for satsuki azaleas

A few months ago, two satsuki professionals visited my garden. The weather was unseasonably warm when they arrived – it reached 102, an unusual high for June – and they were worried I wasn’t watering my azaleas enough. They repeatedly stressed that azaleas don’t do well when they dry out or when it gets too hot. I watered a lot that day.

Just two days later, they awoke to cool, cloudy weather in the low 60s. Too cold, they thought, for satsuki to grow very well. They suggested I look into getting a greenhouse.

Fortunately, I had a greenhouse I could use to perform a test. I placed a few azaleas in the greenhouse – some healthy, some weak – while the rest stayed outside under 30% shade cloth.

Two of the trees were exposed root ‘Shirokozakura.’ They had both leafed out well in spring but neither had produced elongated shoots. Here’s what they looked like this month.

Exposed root satsuki azaleas – ‘Shirokozakura’

One of the trees was in a greenhouse but didn’t receive much fertilizer. The other tree stayed outdoors but was fertilized regularly. Any guesses which is which?

I removed the elongated shoots as they won’t be part of the trees’ final design. The tree on the left had about ten of these shoots while the tree on the right had almost thirty.

Lots of long shoots

After removing the long shoots – 18″

I also compared the foliage between the two trees, but there the differences were subtle. The tree with long shoots had slightly smaller leaves, while the tree with fewer shoots had larger leaves. Does this change your guess?

It turns out the tree with the long shoots – and smaller leaves – was the one in the greenhouse.

It’s tempting to say the greenhouse produced growth that I’m not interested in keeping – the long shoots – so I’d be better off keeping my azaleas outside. Long shoots, however, are a sign of general vigor in azaleas, and the more vigorous the tree, the better it can respond to training as bonsai.

I can also note that we had a great summer this year. It’s not uncommon where I live for summer days to start out cold and cloudy and then warm up in the afternoon, but this year was consistently warm (as attested by my farmer’s tan).

If we were in for a cool summer, I think satsuki azaleas would do well in a greenhouse where I live. The ideal greenhouse would have retractable walls and/or roof so the trees could get sunshine when it’s available and warmth when it’s cloudy. But given the subtlety of the differences, I’m happy to keep my azaleas outdoors for the time being.