It looks like many residents in my block have green fingers. There are a few levels with a lot of plants along the corridor. On one level, 90% of the flats have plants outside.
Maybe some of these residents have been living in the kampong before they moved to high-rise flats. And they were used to growing plants and rearing fowl in the compound of their houses.
If the HDB allows it, I guess some households might rear chickens in their flats. Someone might even keep an old cock with a powerful crow to use as an alarm clock to wake up the family every morning.
(If you buy a male chick and take good care of it, it will become an old cock in about 8 years, which is equivalent to about 70 years for human. If you would like to see an old cock, there is a picture and a story about it here.)
Here are three of the levels in my block with a lot of plants, some very tall, but they are quite neat and tidy ...
A mini garden ...
This level is the only exception, no shoe racks and very few footwear outside but there are still a few pots of plants at the further end.