Gherkins are a pickling cucumber. Cucumbers are actually a tropical plant so are not going to want to be planted out until temperatures have risen. By all means start them from seed now but keep the babies under cover for a few more weeks. But is it worth growing gherkins at home? Fresh, home pickled gherkins should always taste much better than those commercially produced but you have to be pretty passionate about them to want to grow them yourself. Just don’t make the mistake of thinking you will put in one plant because then you will get a few baby gherkins every few days whereas what you want is plenty of them all at once so you can start the pickling process. You probably need about five plants, each of which will take up a square metre, and then pull them out and compost them as soon as you have harvested sufficient quantities.
All the cucurbits are gross feeders (hungry plants) so they need rich, fertile soil in full sun with plenty of depth to get their roots well down. They also need plenty of water during the heat of summer but as they are prone to mildew and all sorts of nasty diseases including Fusarium wilt, you are best to direct water to the root zone and avoid wetting the foliage. Keep the sprinkler well away. You can train the runners over a frame or structure to reduce the amount of ground space required or you can just leave them to sprawl over the ground like pumpkins. Personally, I think it is worth making more effort with a few cucumber plants which will gently crop from January to early April, when salad veg are most in demand. I am particularly keen on the little Lebanese cucumber. But then I would say that because we have neighbours who adore pickled gherkins. We make land available, they grow them and pickle them and give us a jar or two.