some species of purslane are not particularly edible. Although as far as I know the genus as a whole doesn't produce any truly toxic compounds, some have extremely high levels of oxalates. Portulaca amilis is an example of this, while its not actually "poisonous" the few sources I've seen about its edibility more or less boil down to "it will feel like chewing on raw taro, even when boiled and drained twice".
the most common edible purslane has very tiny flowers, not at all showy.