Garden gadgets - thermometers

It’s that time of year when you can step outside wearing a thick jacket, woolly hat and gloves and half an hour later you’ll be standing there in a T-shirt, having cast them all aside.  April’s weather has a reputation for being changeable and keeping gardeners on their toes - it could bring an early heatwave, but a late frost can’t be ruled out either.

One way to help you navigate the ups and downs of the UK’s spring climate is to arm yourself with a thermometer.

If the weather has been on the cool side, how can you know when it’s time to sow direct into your vegetable beds?  A soil thermometer will help: simply plunge the end into the ground and wait for a stable reading.  You’re looking for a minimum of about 7°C, as most seeds won’t germinate below this.

Similarly, when spring days flood the greenhouse with light and heat, how can we be sure it’s ready for seedlings that need plenty of warmth, like tomatoes and chillies?  Night time temperatures can still drop too low, stalling growth or, worse, freezing the young plants.  A greenhouse thermometer is a must - one which registers and records the highest and lowest temperatures reached.  When your greenhouse stays consistently above 10°C overnight (and preferably higher, between 15-18°C), then you can consider moving your tomatoes in.

Finally, compost.  A well-constructed compost heap with the right balance of ingredients should be warm - between 55-65°C - to encourage beneficial bacteria to decompose the material efficiently.  Too cold and everything slows down; too hot and the bacteria will die off.  A compost thermometer with a long probe can help you monitor the conditions in the middle of your heap, ensuring it’s warm enough to kill off weed seeds and disease, but not so hot that it’s harmful to the process.