Real science! Life in the post-apocalyptic wasteland...

From Atomic Rockets, bamboo might be a common building material:
Growing a Colony - Bamboo

Fast growing, can handle a variety of soils, useful for building material, filtration, charcoal type fuel, paper, clothing, and bioethanol type fuel.  The disadvantage is that it grows tall, so it might cover attackers headed to a village.  But if the village already has fruit trees or other tall structures around, that would be an acceptable loss.
(the rest of the page covers other topics of colonization such as the effective population number, expendable gender, low-tech solutions allowing freedom, high-tech solutions needing more labor to startup than available, dart guns/crossbows for weaponry, startup supplies, slave economy, small-group psychology, consul resolutions vs dispute resolution, and Living Systems modeling)


The other idea would be using hemp and products to maintain a town/city:
Hemp Basics - Information (produces more fiber than cotton, or more paper than trees, grows faster than trees, hemp seed flour, oil can be extracted from seeds to make biofuel, hemp plant itself used to make biofuel, wide environmental tolerance, woody inner core can be used for wall material)
7 uses for industrial hemp (clothing, food/drink, paper, building supplies, plastic, fuel, chemical cleanup)


What other plants would be useful for a post-apoc town to grow?


One fictional idea I found from a Warhammer40k Battlefleet Gothic post about the various factions on a starship (small ones are ~1 mile long and have ~10,000 people IIRC), was one group was the 'Welcomers' group. This is an all-female group whose job is to 'welcome' any male visitors/passengers on board. The resulting children if male are sent to the other groups on the ship according to the other groups' needs. If the resulting children are female they are kept in the Welcomers group. The purpose of the Welcomers is to keep new genes coming into the ship, to avoid inbreeding.


Edit:
One idea would be making planter boxes with wheels on them so they can be wheeled out to grow in the sunlight, but in the evening the plants are wheeled inside the town for safekeeping. If you need more strength, use a relic trailer, where the metal springs and axle allow supporting more weight than wooden wheels and axle allow. If relic trailers would have rusted away, melted metal for springs and making axles could be done instead.

Tanker trucks if available would be used to store water.

The giant mushroom forests always fascinated me in that movie