GardenCalc
Thirty-two minutes of garden number-crunching, powered by NotebookLM's Deep Dive format. Episode 001 covers how the calculators actually work and why getting the maths right matters more than guessing. Why 35g per square metre is all a new lawn needs, why overseeding only needs 15–20g, and the exact three-rule method that takes the guesswork out.
What's in this episode
It is easy to put down two or three times more grass seed than a lawn needs. It feels generous, but the extra seed competes for water and nutrients, chokes the young roots, and leaves you with the patchy lawn you were trying to avoid. This episode works through the real numbers, in plain English, at dog-walking pace.
- The two rates that matter. A brand new lawn wants around 35g of seed per square metre. Overseeding an existing lawn needs far less, roughly 15 to 20g per square metre.
- The 50 square metre example. Overseeding a typical 50m² lawn takes 750g to 1kg of seed. That's about half a standard box, not the whole thing.
- When to sow. Wait for soil temperature above 8°C. In most of the UK that means April to May, with a second window in early autumn.
- The mistakes that cost you. Scattering by eye, skipping the rake-in, and giving up on watering after the first week.
Listen with the free Grass Seed Calculator open. Punch in your lawn area, pick new lawn or overseeding, and it gives you the exact grams you need. No signup, no email gate, just the number. The calculator page also lists the published sources behind each figure.
This episode and these notes are general information only. Always check product labels and your own conditions before acting on specific quantities.
About Garden Maths
Garden Maths is the podcast from GardenCalc — the site with 18 free garden calculators used by over 2,000+ UK gardeners a month. Each episode takes one gardening question and works through the actual numbers behind it.
No fluff. No vague advice. Just the maths that makes the difference between a lawn that works and one that doesn't. Episodes run around 30 minutes, and each one stands alone, so you can start anywhere.
Produced using NotebookLM's Deep Dive format, combining the data behind the GardenCalc calculators with a conversational walkthrough that's easy to follow on a dog walk or while you're potting on.
The show is young. Episode 001 is live, the next episodes are in production, and the plan is a proper season across Spotify, Apple Podcasts and the big directories. If you want to be told the moment a new episode lands, the newsletter below is the way.
Why a maths podcast for gardeners?
Because nearly every expensive gardening mistake is a numbers mistake. Too much seed, too little topsoil, the wrong depth of mulch, a delivery of gravel that is double what the path needed. None of it comes from bad gardening. It comes from guessing quantities instead of working them out.
GardenCalc exists to fix that on screen, with calculators. Garden Maths does the same job for your ears. Each episode takes one question UK gardeners actually type into Google, pulls the real figures from the same data that powers the calculators, and walks through them the way a knowledgeable neighbour would over the fence. You do not need a notepad. The point is that the logic sticks, so next time you are standing in the garden centre you already know roughly what the answer should be, and the calculator just confirms it.
How each episode is made
Every episode starts with the numbers, not the script. We take the published UK figures behind one calculator, sense-check them against sources like the RHS and Met Office data, then use NotebookLM's Deep Dive format to turn that research into a two-voice conversation. The result gets a final human listen before it ships. If a number in an episode ever disagrees with the calculator, trust the calculator, then email us, because one of them needs fixing and we want to know which.
In Production
- Episode 002 Frost dates: why your postcode changes everything about when to plant, and how 30 years of Met Office data turns into one safe planting date for your garden.
- Special The UK peat ban: what it actually means for your garden, why your compost costs more, and how to work out exactly what you need without overspending.
No fixed release dates promised. Each episode ships when the numbers check out. Subscribers hear first.
Get the next episode in your inbox
Subscribe to The Garden Brief and we'll let you know when each new episode drops — plus one free garden tip every Friday. It's the same newsletter read by the gardeners who use our calculators, it's free, and you can unsubscribe any time with one click.
Join The Garden Brief →