I just moved to Cowichan Bay near Duncan and have purchased a Wisteria sinensis "Cooke's Special Purple" that I plan to plant in a 1/2 barrel. It's a large plant with strong and vigorous buds already and in a 7 gal pot. I'm going to train it up onto the edge of the deck sunroof so it hangs down over the deck. I have never grown one before having moved here last November from Manitoba. I can't plant it directly in the soil beside the deck, it's gravel there. Can someone advise me how many holes to drill into the bottom of the barrel and what the most suitable soil mixture would be. I will put about 2 inches of gravel in the barrel over the drain holes. Can I plant annuals in the same barrel at the base of the Wisteria? Thanks in advance.