Forced spuds should be sprouting by mid-February

Still confined to the greenhouse but too soon to sow seeds – what’s a girl to do? I need something to keep me going through the gardening doldrums, so I’ve decided to use a little force.

By which I mean using the relative warmth of the greenhouse to persuade things to get going a bit earlier than they usually would. Permanent crops like rhubarb and seakale are easy-peasy as they live in the soil all winter so warmth for them means spring has arrived – all they need is a bucket over the top and a packing of straw to persuade them to wake up early.

But with a bit more effort and a greenhouse kept just above freezing with a little electric fan-heater, you can also force strawberries – on my to-do list – and potatoes, for which you need no more than a small packet of tubers and a couple of compost sacks.  

This is a great trick for getting very early new potatoes - as long as you get them started by the end of January, you should be harvesting at the beginning of May, a full month before the ones you grow outside are ready.

The first thing to consider is the variety. A super-fast early is usually what’s recommended – ‘Swift’, for example, or ‘Rocket’. But though I’ll admit I’ve never tried growing them myself, I’ve heard they’ve bred out some of the taste in the race for quick maturity.

Though I’d probably get faster results with these types, I want to try a little experiment by choosing ‘International Kidney’, which on paper at least is an early maincrop variety. You’ll probably understand the method in my madness when I tell you that it’s also known as the ‘Jersey Royal’. The flavour should be second to none – yet they should behave just like new potatoes when I harvest them early.

So here’s how you do it:

Place the tubers upright, two to a sack, resting on the surface of the compost

1. If you’re using compost sacks, turn them inside out – this means the black side is facing outwards which absorbs sunshine and keeps it warmer for longer. If you don’t like the allotment aesthetic and can’t hide them away out of sight, you can use the undeniably more attractive purpose-made potato barrel planters or potato sacks.

2. Put your sacks or barrels in place before you fill them – they’ll be far too heavy to move once they’re up and running. Make sure wherever it is that it’s completely frost-free as potato plants are tender. I’ve got mine in a corner of my frost-free greenhouse, but a conservatory would do just as well (as long as you have a very tolerant other half who really, really likes new potatoes). The warmer they are, the quicker they’ll grow.

3. Roll down the top of the compost sack to reduce the height by about two-thirds, and snip some holes in the bottom with scissors to allow drainage. Then fill to about 15cm with multi-purpose compost mixed about 2:1 with a soil-based compost – I used John Innes no. 2.

4. Place your tubers on top of the compost: two per compost sack is plenty, and you don’t have to bother with chitting them as you’re getting them under way so quickly anyway.

5. Now cover them with more of your compost mix so they’re buried by about another 10cm. Water in thoroughly, and keep them damp but not soggy all the time they’re growing.

That’s it! Told you it was easy. I’m looking forward to the first shoots appearing in about three weeks’ time. Once they’ve poked above the surface, the idea is that every time they reach 10cm tall, you roll up the sides of the compost sack a little more and fill to just under the top leaves with more compost. When you get to the top, leave them to flower and then harvest. Now, how’s that for something to look forward to?