If you have a trellis or anything for it to grow up, clematis is a great grower. As you can see from the following pic, which is a bit ott, you can grow two or three colours together...
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I love pyracantha, takes a while to grow, but again you can blend in two colours, but be warned it's a fooker to train in as it has very sharp needles, but again adds colour...
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For something more pot based, this plant will raise a few eyebrows and make you fill chilled out with your rum, on a lovely summers evening....
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