Sow Now uses your garden's own sensors and Growing Degree Day science to tell you exactly when to sow, move to greenhouse, plant out, and harvest — personalised to your variety, your microclimate, every morning on your phone.
From £199 one-off · £4.99/month · No gateway required · Works with Ecowitt sensors
No command lines, no config files, no engineer required. Your kit arrives ready to go.
Connect the USB-C cable. The hub creates its own Wi-Fi hotspot called SowNow-XXXX. Connect your phone to it and enter your home Wi-Fi password — takes 60 seconds.
Visit app.sow-now.uk on your phone and scan the QR card in the box. The app links the hub to your account in one tap.
Push soil probes into your beds, mount the weather station outside, clip the greenhouse sensor to a frame. Fully wireless — batteries last 12+ months.
Open the app to find three specific things to do today, generated from your actual garden's data overnight.
The Ecowitt WS69 station reads the temperature, humidity, wind, rain and UV your plants actually experience — not an average from a station 10 miles away.
A wireless capacitive probe in each bed tells you exactly which one needs watering — not a general garden average. No wasted water, no stressed plants.
Your greenhouse can be running 80+ GDD ahead of the garden. Sow Now tracks both zones independently so you know when seedlings are truly ready to move out.
Tell Sow Now you're growing Gardener's Delight tomatoes or Charlotte potatoes — it calculates exactly when to sow, move to greenhouse, plant out, and when to expect your first harvest, based on your actual GDD accumulation. Not a generic calendar. Your garden.
Seeded with curated data from DT Brown, Thompson & Morgan and Kings Seeds — covering tomatoes, potatoes, peppers, beans, brassicas and more. Can't find your variety? Add it. Every customer contribution improves the predictions for everyone.
When your sensor reads below 2°C, you get an alert before it happens — not after. Enough time to cover vulnerable plants.
The Sow Now hub receives your sensor data directly over radio — your readings go straight to your account. Ecowitt's servers are never in the loop.
Sow Now uses Ecowitt sensors — a widely available, well-supported range you can buy yourself from Amazon, eBay, or direct from Ecowitt, or purchase pre-configured as part of one of our kits. No proprietary hardware, no lock-in. Our recommended starting setup for a typical greenhouse garden is listed below.
One per site. Mount outside on a post or fence, clear of walls and overhangs. Reads air temperature, humidity, wind speed, rain, and UV. This is the foundation of your garden GDD calculation — one WS69 covers your whole plot.
Garden zone · 1 per siteWe recommend starting with two WH31s. Channel 1 goes in the greenhouse — hang it out of direct sunlight to track greenhouse GDD separately from the garden (your greenhouse is often 3–6 weeks ahead). Channel 2 sits on the indoor windowsill where you germinate seedlings — the environment there is warmer again, and your seeds will tell you when they're actually ready to move, not just when the calendar says so.
Greenhouse zone Indoor seedling zoneWe recommend starting with two WH51s. Push one probe into a planter in the greenhouse and one into a bed in the garden. These two locations have very different watering needs — the greenhouse planter dries out faster and the garden bed holds moisture longer. The app tracks each one independently and tells you exactly which needs water and when. Add more sensors as you expand — they're available separately.
Greenhouse planter + garden bedPlace on any windowsill facing the garden, plugged into USB-C. The built-in radio receives all sensors simultaneously at 868 MHz — no wires, no gateway, up to 60 m range.
Receives all zonesSow Now keeps a running diary for every crop — logging each milestone against real GDD data from your garden. No more guessing whether your timing was right.
When you tap "Germination confirmed" or "Moved to greenhouse", Sow Now logs the date and the exact GDD your garden had accumulated. Next season you'll know exactly what conditions produced your best results.
Your greenhouse accumulates heat faster than the open garden. Sow Now tracks both and tells you when your greenhouse-grown seedlings have actually hit the GDD threshold to move outside safely — not just a calendar date.
Today's three actions are generated from your live sensor readings — soil moisture, accumulated GDD, wind speed, and what stage your crops are at. Not a generic growing calendar.
Based on GDD accumulated so far and your crop's target, the predicted harvest date adjusts every day as your weather changes. A cold spell pushes it out. A warm week pulls it in.
A tomato sown on 1st March doesn't know it's March. It knows how many warm hours it's experienced. That's what Growing Degree Days measure — accumulated warmth above the temperature at which a plant starts growing. Two gardens 400 miles apart can have completely different growing seasons, even if they plant on the same date.
At 1,380 GDD for the season, a Surrey garden comfortably hits the 1,200 GDD target by mid-August. Sow indoors in March, transplant in May, pick from late July.
At 910 GDD outdoors, hitting 1,200 GDD in the garden alone is borderline. But a greenhouse in Cumbria might add 300+ GDD. Sow Now tells you exactly when your greenhouse has reached the threshold — not a calendar guess.
720 GDD outdoors won't ripen most tomatoes. But a decent south-facing greenhouse in Aberdeen can accumulate 1,100–1,300 GDD. Sow Now tracks your actual greenhouse, not an average — and adjusts the harvest prediction as the season unfolds.
Even in the same postcode, a south-facing walled garden can accumulate 200+ more GDD than a north-facing plot. The only way to know is to measure. That's what the WS69 is for.
These are regional estimates, not your garden. The whole point of Sow Now is that your sensors measure your microclimate — the south-facing wall, the sheltered raised bed, the greenhouse that traps heat differently to your neighbour's. Regional averages are where you start. Your sensors are where you finish.
Professional growers have used GDD to predict crop development since the 1950s. It's the accumulated heat energy above a crop's base temperature — a far more accurate predictor of plant development than a calendar date.
The difference is that Sow Now uses your actual sensor readings — not a weather forecast API. Your south-facing greenhouse wall might be accumulating GDD twice as fast as your garden. No weather service can tell you that.
| Crop | Base temp | GDD to harvest |
|---|---|---|
| Tomato | 10°C | 1,000–1,400 |
| French bean | 10°C | 800–1,000 |
| Sweetcorn | 10°C | 1,400–1,600 |
| Pea | 4°C | 1,000–1,200 |
| Carrot | 7°C | 1,200–1,500 |
The kit is yours forever. The subscription pays for daily AI advice and unlimited crop tracking. Cancel anytime.
One missed sowing window or a wasted tray of seedlings costs more than a year's subscription. Sow Now pays for itself.
"I've been growing tomatoes for 20 years and always struggled to know when to move seedlings outside. This year Sow Now told me exactly when — and they were the best plants I've ever grown."
"The soil moisture alerts alone are worth it. I used to overwater half my beds and underwater the other half. Now the app tells me which bed needs attention before I even go outside."
"I already had the Ecowitt station. Setting up Sow Now took less than 10 minutes. The fact it doesn't use the Ecowitt app or cloud is a big deal for me — everything stays on my own system."