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How to play Photosynthesis (2026): Photosynthesis is a strategy game for two to four players, ages eight and up, about trees competing for sunlight. The sun moves around the board each round, trees earn light points when they are not in shadow, and you spend those points to plant, grow and collect trees for points. This guide follows Blue Orange’s official rules.
Get the game: Photosynthesis
The box includes a forest board, a sun segment, four player boards, 24 seeds and 56 cardboard trees in three sizes. It sets up in a few minutes and looks gorgeous as the forest grows.
Price band: $30+ (about $43) · Check today’s price on Amazon
What is in the Photosynthesis box
- 1 game board, 1 sun segment and 4 sun revolution counters
- 4 player boards, 4 light point trackers and 1 first player token
- 24 scoring tokens in four stacks by soil richness
- 24 seeds, 32 small trees, 16 medium trees and 8 large trees (in four tree varieties)
Setting up Photosynthesis
- Each player takes a player board, a light point tracker, 6 seeds and 14 trees (8 small, 4 medium, 2 large) in one variety.
- On your player board, fill the spaces with 4 seeds, 4 small trees, 3 medium trees and 2 large trees. Set your tracker to 0. The rest (2 seeds, 4 small trees and 1 medium tree) sit beside your board as your available pieces.
- Stack the scoring tokens into four piles by leaf count, highest values on top.
- Taking turns, each player places one small tree on an outer edge space of the board, then a second one.
- Place the sun on the sun symbol and set the first, second and third revolution counters nearby. The youngest player takes the first player token.
Two players: leave the three darkest 4-leaf scoring tokens in the box. When a player collects from the center, they take from the 3-leaf stack instead.
A round of Photosynthesis
Each round has two phases: photosynthesis, then the life cycle.
Phase 1: photosynthesis
The first player moves the sun one position clockwise. Skip this in the very first round. Every tree not in shadow earns light points: 1 for a small tree, 2 for a medium tree and 3 for a large tree. Seeds earn nothing. Move your tracker up, but you can never hold more than 20 light points.
How shadows work
Trees cast shadows on the side away from the sun. Small trees shade 1 space, medium trees 2 and large trees 3. A shadow only affects trees that are the same size or smaller. A taller tree in a shadow still earns its full light. Trees can shade trees of their own variety.
Phase 2: life cycle
Starting with the first player, each player takes as many actions as they can afford, then passes to the left. You may not act on the same board space twice in one turn.
- Buy: pay the price printed on your player board to move a seed or tree to your available area. Buy from the bottom of a column up.
- Plant a seed: pay 1 light point to place a seed near one of your trees: 1 space from a small tree, up to 2 from a medium tree and up to 3 from a large tree.
- Grow: replace a piece with the next size from your available area. Seed to small costs 1, small to medium costs 2, and medium to large costs 3. The replaced piece returns to your player board if there is room.
- Collect: pay 4 light points to remove a large tree and take the top scoring token from the pile matching its soil. The center is richest, and the outer ring is poorest.
At the end of the round, pass the first player token to the left.
Final scoring in Photosynthesis
When the sun completes a full lap, remove a revolution counter. The game ends after three laps, which is 18 rounds. Add up your scoring tokens, plus 1 point for every 3 unused light points. If players tie, the one with the most seeds and trees on the board wins. If that ties, the players share the win.
Advanced Photosynthesis rules
- Add the fourth revolution counter for a fourth lap of the sun.
- Forbid planting or growing on a space that is in shadow.
Photosynthesis tips
- Plan for where the sun will be next round, not where it is now.
- Plant toward the center early. Those scoring tokens are worth the most.
- Do not collect too early. A large tree earns 3 light every round it stays.
- Use your big trees to shade rivals, but watch your own small trees too.
Compare it with another garden favorite in our best tile-laying board games list, or see best family board games.
Photosynthesis rules questions
How many rounds are in Photosynthesis?
Eighteen: three full laps of the sun around the board.
Can a tree be shaded by a smaller tree in Photosynthesis?
No. Shadows only affect trees of the same size or smaller.
What is the most light points you can hold?
Twenty. Any extra light points earned are lost.
Do unused light points score in Photosynthesis?
Yes. You get 1 point for every 3 unused light points at the end.
