How do I win level 5 (Grey Void) in Eufloria?

I have colonized every landmass on the level and have 3 trees on each. All of them have capped at 40 seedlings, so there's nothing left to do. How do I win this level?

Solution 1:

About midway through the level, you gain the ability to plant Defense Trees. Are you planting any of these? I think one of the requirements to clear the level is having a few of these, although I don't know what the exact quantity is (2, I think?).

Here's the popup:

At about a minute past this bookmark, the player gets a second popup saying "Excellent, you have planted several DEFENSE TREES..."

Solution 2:

You can unlock the next set of levels so you can just skip lv 5. For me it was that or uninstall. Not going to replay a level because of I didn't plant enough of a certain type of tree and can't replace old ones sigh. What an oversight.