Cut down every tree that looks dangerous, and November knocks over more of what's left.

Why the chainsaw loses

The obvious plan is to take down anything that looks risky. I wrote that plan into the game as a scripted hand, and it's the second-worst hand in it. Over the same 100 storms it takes 4.7 trees a season from the ground, and November still knocks over 4.7 more. The hand that never takes a tree down, and spends its days pruning, cabling and reducing instead, loses 2.7. Doing nothing at all loses 5.9.

Three rules do it:

• A stump is a gap. Every tree you take opens the wind onto both neighbours for the rest of the year. Each open side adds a tenth to the gust that tree feels. In a 70 mph storm that's 7 mph.
• The street watches. Take a tree that rates High or Extreme even at best and the street loses one point of goodwill. Take anything else, including a tree that's only High at worst, and it loses three: "You took the cherry at no. 6 and it was fine. We watched you do it."
• Angry streets cost days. At 3 points every job there takes an extra crew-day, because nobody moves their car for your truck. At 2 there's a petition in and the council won't sign removals at all.

So the chainsaw hand burns its days, loses the street, and leaves a row of exposed trees nobody will let it touch. It pays $92,160 in claims on average. The hand that never takes one down pays $60,040.

From the ground, every rating is a guess

Each tree has a card. It lists what you can see from the pavement (a cavity, bracket fungus, a split trunk, a lean) and what's underneath: a back garden, parked cars, a house, the school crossing. Two published matrices turn that into a rating: Low, Moderate, High or Extreme.

The catch is that you can't see inside the trunk. So the card shows a range. The London plane at no. 14 Quarry Lane has a cavity, and from the ground it holds anywhere from 66 to 91 mph by November. That's High at worst and Low at best. One crew-day up a ladder and the range becomes a number: 69 mph. High.

Now you know. And if you take it down, the report backs you and the street only loses one point. A climb costs one crew-day, same as a prune, and it's the job the obvious plans skip.

The game's no-climbing version of Marge's rules loses to the real thing on 97 storms out of 100.

Six jobs, sixteen days

March gets 3 crew-days, May 4, July 5, September 4. Each job acts on one tree.

Every month a smaller wind blows first (44, 40, 34, then 46 mph) and the street shows a red ⚠ on whatever it will break, given what you know. That's the same rule November uses, at a smaller number. You learn the table before it matters.

The streets keep score, and an angry street costs you days

Mercer Street is old houses and retired teachers who are proud of their canopy. Quarry Lane is terraces, shift workers and cars parked nose to tail. School Row is the primary school and the parents at its gate.

Each street has a goodwill score from 0 to 10. Get one up to 7 and a resident starts ringing in the worst hidden defect on their street, free. It counts as a climb. Let one fall to 3 and you start hearing about it:

"Nobody's moving their car for your truck, warden."

The truck turning up on a street for the first time in a month is worth a point. So is a ribbon. A whole tree landing on anything but a back garden costs one. Limbs only cost one if they hit a house or the school crossing. Break a promise and it's two.

In November, the council reads your list back to you

There's nothing to do in November. You watch. The storm is fixed before March (63 to 77 mph, from the west, northwest or southwest), so the same year always brings the same storm. Then the council meets and names the trees, worst first. These are real lines from one season played with Marge's rules:

• "The ash at no. 18 Mercer Street went over at 69 mph onto the road: $20,000 in claims. You'd climbed it in May, so you knew."
• "The silver maple at no. 10 Mercer Street took 72 mph and stood. Without the cable you put in in May, it wouldn't have."
• "The crossing lime stood, as you promised School Row in March."

That first one is the warden's own hand. It climbed the ash, reduced it, and lost it anyway. The council doesn't grade on effort. Its verdict is next year's tree budget, and that's your score: one star at $120,000, two at $180,000, three at $225,000. It can go below zero.

For arborists and tree officers: what's real and what's a game number

The two rating matrices match the ones in ISA's Tree Risk Assessment method, cell for cell: likelihood of failure × likelihood of impact, then × consequences, to Low, Moderate, High or Extreme. Its category names (imminent to improbable, negligible to severe) are the game's too. I'm not affiliated with ISA, and the game isn't a training tool.

Here's what's a game number and not your world:

• Strength is one figure in mph: the gust at which the whole tree goes over. Real failure isn't one number.
• Likelihood of failure is read against one fixed storm outlook, not a timeframe you choose.
• Cabling adds 16 mph to a split trunk. Reducing adds 13. Those are tuning, not engineering.
• Decay only grows on two signs (bracket fungus and crown dieback), a little each month.

What I hope rings true is the rest: that the list is political, that a removal needs a reason people can see, and that the tree you climbed and still lost is the one you'll have to explain.

Six bots, the same 100 storms: the ladder beats the chainsaw

The game ships with six hands that play its real rules. I use them to check the game is fair before anyone plays it. These are their averages, not what a person scores. In trees: the chainsaw bot ends the average year with 8.6 of 18 standing, and Marge's rules keep 14.7.

Marge's rules earn three stars on 41 storms of 100. No hand wins every storm: on the first twenty, Marge's rules top the table 14 times, ribbons 4 and never-take-one-down 2. Different storms want different lists. It isn't only the average: the chainsaw bot loses more trees in November than the never-take-one-down bot on 83 storms of 100.

Plain answers

What does it cost?

Nothing. No account, no ads. It remembers your best budget, how many seasons you've played and whether you've seen Marge's notes, in your browser, and that's all.

How long is a season?

Four work months and a storm. Most of the time is reading cards, and I'd guess 15 to 20 minutes for a first season. When it ends, the next year brings a different storm.

Does it work on a phone?

The box at the top does, start to finish. For the full game you want a keyboard: arrows to choose a tree, a letter for each job, space to send the wind.

Is it just dice?

The hidden insides of each tree and the storm are fixed when the year starts. Those red ⚠ marks are the sim's own preview, and a climb removes the guess. What's left to chance is whether a falling tree or limb hits what's under it, and the card gives the odds as "impact: high."

Do I have to know anything about trees?

No. Marge, the retired warden, leaves you notes through the first season, and every card says what's wrong in plain words.