General Strategy

The key build pattern is to separate each of your trees by a "Y" shape move (two spaces away in 2 diagonal directions) such that they will never block each others light. Naturally everyone will be trying to do this which inevitably leads to contested tree spaces.

Always think about what your plan is on the next turn. How much sun will you get? If you're playing with heavy shadow, which of your trees will you be able to grow? To accurately answer both of these questions you need to consider the turn order and make educated guesses about where your opponent(s) will grow. This is something you build an intuition for over time, but generally imagine you were them. Where would you want to grow? Check how much sun they have and what trees they have in stock to determine what they're capable of. This has a major impact on where you want to grow so that you are not blocked and/or you can block them.

It's worth emphasizing how important the turn order is as well. If you're going first in a round, you get first pick of spaces to plant seeds and grow your trees without being shadowed by opponents' growth and the opportunity to cast shadows on where they want to grow (heavy shadow). But going last can be good too. Imagine you have 2 different trees that you could grow. Either could be shadowed or in the sun on the next turn depending on which trees your opponents choose to grow. If you go last, you now have full info to grow the correct tree to gain sun.

Note: most of this advice is written with 3-player, 3-round heavy shadow games in mind as that's currently (April 2023) the competitive format. In 2-player games the board is much less contested and players are more free to expand. Without heavy shadow there's generally much less thinking required.

Early Game

On your first turn, upgrade a small tree to a medium tree. This leads to additional sun income but more importantly lets you plant seeds 2 spaces away (Y shape). It is often better to stake your claim over a spot by planting a seed than it is to upgrade your tree for more sun. Your additional trees in prime locations will lead to more sun in the long-term. Don't get greedy with maxing early sun; take the prime real estate while it's available.

It may seem like going for the center in 3+ player games is crucial, but there are often situations where you can never grow your seed (assuming heavy shadow) as it's easy to be surrounded on all sides.

Mid Game

Your goal should be to get all your level 2 and 3 trees on the board. Until you have done this you should never be scoring your trees. This is a waste of sun both in that you could have spent it on growing your engine and you've thrown away the 3 income that tree produces. Once you have spent all your level 3 trees and there's nowhere left to build 2's then you have no choice but to start collecting. Even then you should be checking your sun limit of 20. If the next turn's sunlight does not put you over 20, do not collect. In some cases even if it puts you 1 or 2 over, waiting to collect may be better. Think carefully before planting any seeds toward the end of round 2. If they do not (a) net you 5 sun (the cost to plant a seed and level 1 tree) or (b) have enough time and sun to be grown to level 3 and collected, then you should probably not build it. In very rare cases planting a seed just to block an opponent's potential tree may be beneficial but probably not.

Late Game

The last round of the game is all about carefully growing and collecting your remaining trees. Leave up the trees that block your opponent's sun and collect the trees that block your own sun ideally on the turn right before this would occur. In heavy shadow you also need to make sure you can both grow and collect your trees since both actions are potentially blocked by opponent's taller trees. The key threshold each turn is 12 sun. This is how much you need to collect a tree, re-buy that tree, and plant it (4+5+3). Aim to do this as many turns as possible in the final round and you should at least be a contender for victory.