In the very beginning, do not plant any trees right away. Prepare to send your seedlings to the attacking asteroid the INSTANT you see them move toward your asteroid. AS SOON AS you capture the new asteroid, IMMEDIATELY send ONE seedling to the outer asteroid containing your reinforcements. AS SOON AS you reveal the new seedlings, send them to your other asteroid as reinforcement. Depending on how quickly you have moved so far, the scripting behavior seems to be less predictable from this point forward.
My success at this level follows this basic strategy:
Try to keep a minimum of 25 seedlings available at all times to attack an unoccupied asteroid, building Dyson trees when possible on your strongest asteroid (in order to create the strongest seedling force possible). If you have a flower, plant it on the strongest asteroid to build enhanced seedlings- I wouldn't waste time on Defensive trees on this level. Be patient. Allow the other factions to attack each other and become weaker in number. If they abandon an asteroid and you have enough seedlings, attempt to take over the abandoned asteroid. They will be too busy attacking the other asteroid to defend the one they just left- but you must be quick. AS SOON AS you capture another asteroid, send a SINGLE seedling to the newly-reachable outer asteroid to reveal your additional reinforcements. Don't waste seedlings building trees on the weaker, outer asteroids. Always be prepared to retreat if necessary, and re-attack if the opportunity arises. Since you start out so weak, every seedling is precious. If one of your asteroids is under attack by a superior force, and you have retreated, remember that it is still generating seedlings until it is captured. Keep dragging the newly-born seedlings away to safety as long as you can.
Eventually, with just a little luck, you can avoid being wiped out long enough to build up an undefeatable seedling army. Gaining access to the reinforcements in the perimeter asteroids is crucial. If you find yourself isolated and weak-in-number on an outer asteroid, just quit and start over.
