Well i'm not a veteran, i started writing yesterday so take what i say with two grains of salt, however i do think that the idea of a city seed seems pretty interesting, you also did a pretty good job of writing about what it is and what it looks like.
There is one thing though, your containment procedure mentions that planting of this SCP is prohibited unless authorized, so i'm assuming the seed is still in its dormant state, but in the description its mentioned that the seed's power "become evident when SCP-XXXX is planted beneath at least 0.25 meters of soil in a location that is at least 4 kilometers from any permanent man-made structure.", how would they know something like this if the seed hasn't been planted yet? Does this mean that the seed can simply be retrieved after the city has grown? Or is it that the original Cocos nucifera to which it gave origin grew more of these city seeds?