I have to call BS on this however.
Recently I wanted to plant a few radishes to try a new pickles recipe I came across but didn't have any spare containers, so I decided to plant some around some tomato seeds in a container. The recipe called for 20 radishes so I decided to plant 2 seeds in each of 12 holes in an area the equivalent of 60cm x 5 cm around the edge of the container and well the results speak for themselves:
Lots of good growth and healthy looking leaves:
[img]https://i15.photobucket.com/albums/a360/SamhainP8/Veggie/Radish.jpg[/img]
No problems at all with adjacent bulb growth:
[img]https://i15.photobucket.com/albums/a360/SamhainP8/Veggie/Pair.jpg[/img]
A massive harvest from an area of 60x 5cm in just 5 weeks:
[img]https://i15.photobucket.com/albums/a360/SamhainP8/Veggie/Radishout.jpg[/img]
Give it a try
