Why would I want to plant fungus in SMAC (Sid Meiers' Alpha Centauri)?

The answer to this question got me to thinking.

When playing 4x games, I only ever play the faction which has an advantage in knowledge - which got me to thinking and asking this question

For a decade or so, I used boreholes extensively and was always overrun by mindworms.

Now I still use them, but then remove them as I develop other energy sources.

One thing I have never done, in twenty years, is to plant a single square of fungus.

I felt that doing so might be of benefit to the Gaian faction, but have never played that faction.

Would planting fungus help other factions? If so, how? Wouldn't doing this just spawn more mindworms?

There are many reasons why planting fungus squares might be a good thing in SMAC.

In the early game playing as an eco-friendly faction like the Gaians, or using social engineering (green) so you are Planet friendly gives you a large chance of capturing native mind worms when you attack them. One early game strategy is to take your starting scout, walk through fungus until you find a mind worm, capture that worm, and then use the captured mind worm to capture another, and so on. Every combat with a new mind worm has the chance of capturing that worm, making your worm unit bigger/stronger or giving you free energy credits. If the worm gets too damaged, just set them to 'hold' for a few turns. Worms regenerate health in fungus squares.

As long as any units are captured far enough away from your cities, they are captured as 'independent' units, and don't require any mineral support. You can use these early game "free" worm units for exploration and pod popping, and also to terrify any other faction with your military might.

Native life such as mind worms treat movement through fungus squares as roads (only 1/3 movement per square), while non-native (normal) land units treat fungus as barriers (one square per turn even for fast units). The secret project 'Xenodome Project' allows you to move any and all of your land units as though fungus were roads, so once you get that you have a huge mobility advantage vs. any other faction in fungus infested areas.

In the late game, some research and secret projects make fungus squares even better than forest squares for harvesting minerals and energy. And fungus, like forest squares, makes Planet happier and less likely to retaliate with a bunch of pissed native life.

And don't forget the fun of planting fungus around an enemy city and wrecking their resource income. And since fungus spreads (and destroys any improvement on the squares it spreads to) eventually their city will very weak indeed.

I like planting fungus as much as possilbe in my border cities when playing some nature based fraction like Gaia. Basically turn your border cities into a very hostile enviroment to invade. I carefully calculate how many productive squares I need and turn the rest in fungus. Maybe even keep a small city with a lot of fungus at the border

Your troops are hidden in the fungus I think. Only when the enemy tries to move into the square or you attack do they know you are there. If you use worms in fungus they moves a lot faster in the fungus and normal troops are at a disadvantage when fighting in fungus against worms. The fungus then also supplies you with free troops in terms of worms if you can capture them.