Not often considered a worthy greenhouse subject the humble potato can actually be a rather rewarding crop. Really freshly dug new potatoes are delicious. Much better than those from out of store, or even those just dug a few days before. Well with a frost free greenhouse you can already be eating your own new potatoes when everyone else is only just starting to plant theirs!
We grow potatoes not from seed but from small potatoes called sets. Usually these are planted outdoors around Easter with quicker varieties, Earlies, producing their crop of new tubers from early summer. (Mains or Lates take longer and yield more but often suffer losses from Blight.)
Fortunately in a greenhouse we can start months earlier, our sets can be started just before Christmas and then in batches weekly to give new potatoes to eat from Easter!
Many Early varieties are good under cover but especially Rocket which has long proved fast and reliable. However there are many others with a wonderful range of tastes and textures.
Ideally buy commercially grown sets (however self saved are fine but preferably not supermarket ones which risk importing pests and diseases.) Plant sets about finger deep in rich free draining compost in very large pots or small buckets apiece. Keep in a very light, not too warm position and water sparingly, later as the plants grow feed and water more heavily.
Start a couple of tubs every week or so from the shortest day and you have a succession of plants cropping from Easter on. Cunningly, you don’t need destroy your plants to get your first pickings. As they’re in tubs you carefully de-pot, take any bigger spuds you see then re-pot to let the rest swell the more.
Once outdoors becomes frost free again in mid spring there’s little advantage continuing to start yet more plants under cover. However you can plan a late crop starting new tubs again once summer is over. Keep back sets from the spring planting (store these chilled in the dark or buy the commercially prepared ones) then start planting these in tubs in the greenhouse just before autumn. These plants started from late summer will give you your own fresh dug new potatoes for next Christmas.