The Grow HAT Mini (£30 / $34) in this kit provides a straightforward means of monitoring the moisture levels of up to three plants at once. It can either be used with your existing plants, in which case you will only need the standard £30 Grow Kit, which includes three moisture sensor sticks and cables. Alternatively, there are herb and chilli-growing kits, costing an additional £9.90 ($10.30) each.

We tested the Grow Herbs kit, reasoning that the selection of basil, rosemary, and coriander would require quite diverse growing conditions and need different watering routines. 

The Grow HAT Mini is sized for use with Raspberry Pi Zero but works with any Raspberry Pi with a 40-pin GPIO header. Setup involves updating Raspberry Pi OS (as with any software install) and entering the install code into terminal then rebooting. Once set up, the whole caboodle can be run headless (without a monitor) from a USB power supply. 

If you’ve got the herb or chilli kit, you need to soak the Cocopress soil tablets in water to rehydrate them before planting the seeds. Label the three seed sensor sticks and gently attach them to the respective plugs on the HAT – rather fiddly as the plugs are tiny – and then insert them into the soil. A tiny (0.96-inch, 160×80 pixels) IPS LCD screen on the HAT immediately indicates whether each pot’s soil is wet enough. Blue means too wet while yellow or amber indicates it’s too dry.

Soily something wrong

Should the saturation level of any of the plants being monitored fall below the threshold, the Grow sensor issues a sonic alert – three short beeps at roughly three second intervals – and a blue bell icon appears on the Grow HAT’s display. To deactivate the alarm, just press the cream-coloured button adjacent to the bell. If you don’t water the plant within a few minutes, the alarm will sound again. 

If the plant in question thrives in a dry environment or, conversely, prefers to be pretty damp, you can adjust the saturation level at which the Grow HAT triggers a warning. Pressing the A button on the HAT cycles through the percentage moisture level of each pot and also takes you to a Settings menu where you can fine0-tune the saturation levels for each plant so the alert doesn’t constantly trigger for your desert-loving aloe vera.

Verdict

8/10

We were very impressed with the kit’s ease of use, aided by a foolproof online installation guide. There were far too many seeds for the size of the pots that came with the herb and chilli kits, but that simply means you can plant successive sets of seeds.