For the last couple of years, I’ve sown my mange tout and sugar snap peas in lengths of half-guttering. It seems to ensure near 100% germination – especially in the sugar snaps, which I’ve had very variable results with when sown direct. We also get a lot of pea weevil damage at the allotment – those distinct U-shaped bites which make the seedling leaves look very crenellated – and the plants withstand that better if they are bigger when transplanted into pea weevil territory.
(I transplant the pea seedlings when they are about 3 inches tall. I water the plants in the guttering until they are soaking wet, then slide them out of the gutter into a shallow pre-dug. So long as the soil is uniformly very wet the plants slide out with little or no root disturbance.)
I hadn’t thought of starting any other crops off in half-guttering until I was wondering aloud to my plot neighbour why his beetroot were regularly the size of grapefruit while those of mine which germinated were mostly the size of ping pong balls. He suggested sowing the beetroot in half-guttering the same way as with the peas.
In the end I sowed four 1m lengths more or less successionally and while it’s obviously more labour intensive than direct sowing, I got pretty much 100% germination – even from the Burpees Golden variety which are notoriously poor germinators – and a crop which looks as though it’s going to be very uniform in size. I have moved up from ping pong balls to tennis ball sized roots which is also pleasing and will definitely be sowing in guttering again next year.