Oh I had such plans for that balcony! But then stuff just seemed to get in the way. I did attempt to green it up a bit. Window boxes were bought and two months later filled with soil. And, well, that was it. The most depressing window boxes in the northern hemisphere. Bare save for a plucky self -seeder and pile of old fag butts (cigarette ends for my American friends, who could have an entirely different mental image right now..).
The flower market: This is not usually the place I'd recommend but actually there are some surprisingly some good bargains to be had, more on the window box/bracket side. I have heard mixed reports about the tulip bulbs you can buy, probably better off getting them elsewhere if you want to be sure of what's going to come out of the soil.
Plantenkoning: This fantastic plant shop on the Albert Cuypstraat has something for everyone, small bedding plants, huge palms and some beautiful stone pots. Additional bonus is that it is located close to the excellent Bobs Vlaamse Frites stand.
Intratuin: Really the best in my opinion. A huge place with a great selection of everything, plus an amazing homewre section - Le Crueset, Joseph & Joseph, candles, table linens, oh I just love it. Make sure you take a dutchie so you can utilise their amazing bike skills to carry the spoils home!
And if it's winter so you see no point in trying to grow anything, or you just can't be naffed, then I suggest you treat yourself to a beautiful bunch of flowers from Pompon, the best florist in town (denk ik).