Welcome!
When I think of abundance, I think of a big table full of food. So, in my mind, while growing an apple tree might fall under 'growth', having it weighed down with fruit would be abundance. Having 'more than enough'.
Having a lot of game to hunt etc...
In a way, I could see the waxing and waning of herds and game. So, for instance, having an abundance of deer is good because it provides food for predators but it's bad because it puts strain on the ecosystem as they devastate the local vegetation. Enter the Winter Court and the predators take over and cull the herd. The wolves become too strong creating famine and only the strongest wolves survive(winter's survival of the fittest), and disease (Summer) culls the weak ones. This allows the deer to become abundant.
So the two Courts keep each other in check.
I might just be looking at it from one angle, though. Just guessing, it could also pertain to Places of Power, or temptation to incur debt and to tap into wellsprings of Magical Power. So, maybe, Summer can super-charge things in a way Winter can't? Like how a small fire can go wildly out of control if you're not careful.
