As I started to grow seed one of the first lesson I learned was that seed crops need more space than market vegetables. There are a couple of reasons for this:
1. Seed crops need more space
We grow hundreds of bunches of radishes for market and CSA every week. To get those bunches we need a lot of root in a little space. We grow radishes 3-5 rows in a 30” wide growing space seeded at about 20 radishes per rowfoot. That’s 6 –10000 radishes per 100ft bed.
Radishes gone to seed are 3-4 ft tall and sometimes as wide. We start radishes for seed production as we do bunching radishes. Then, we harvest them, select the best roots and replant the radishes 2 rows per bed with one radish every 18” in the row. This comes to 133 plants per 100 ft beds. A small fraction of the roots in a bed of radishes for market.
On the other hand, tomatoes are grown the same way as a vegetable and for seed since you harvest the fruit in both cases.
2. Seed crops need good ventilation
In humid climates like ours, we have heavy morning dews, frequent sometimes-torrential rains, and even on hot sunny days the air can be sticky. This humidity gets trapped in the plant canopy, and without good air circulation it won’t dry out. These are prime conditions for bacterial and fungal diseases.
This is problem enough in vegetable production. When it starts raining in the summer one of our biggest problems is Sclerotinia (white mold) in beans. In wet period of the summer we often find rampant white mold in our snap beans at the first picking. We offset this by seeding beans every two weeks and always harvesting from young plants before older infected plants to minimize spreading disease. These are adequate measures for snap beans.
Beans for seed need better conditions than snap beans. I planted my first bean seed crop at the same density I would for fresh snap beans (8-20 seeds/rowfoot). After a summer of hot wet weather the bean plants had almost turned to jelly – there was nothing to harvest.
Now I space the plants 6-12 inches apart. Disease pressure has dropped with this new spacing. More space also lets me better evaluate individual plants and rogue out diseased plants to leave the more resistance for harvest. Our bean seed yields have become standard with what I see in books (1400 – 2300 lbs/acre – though I only grow 1/10 of an acre).
Moral of the story: Give your seed crops more space!
Next on going to seed:
And a few more thoughts about seed disease management.