direct seeding fall brassicas

Alex McGregor waldenfarm at
Tue Jun 20 14:13:28 EDT 2000


We have the same problem in zone 7 (really closer to 6 with the altitude).  Our Fall snow
and sugar snap peas were getting killed by early freezes before we harvested because we
had to wait for the soil temperatures to go down to plant.  (We transplant brassicas and
most other things and direct seed beans and peas.)

I came up with a way to get them to germinate in hot weather so they would produce
earlier.  Now we plant these a month earlier.  I plant in beds and then irrigate- using
the water to cool the soil.  Then I immediately cover the beds with a temporary shade
house made out of 1/2" PVC electrical conduit and 80% shade cloth.  I use pieces of 1/2"
rebar in the edges of the beds to anchor the hoops and spring clamps to hold the shade
cloth on the hoops.

The shade tent keeps the soil cool by blocking the sun from heating the soil.  I irrigate
to keep it cool until I see the first sprouts coming up.  By then all the seeds that are
going to germinate are doing it and I remove the shade to keep the first sprouters from
getting "leggy."

I would suggest you get a soil or compost thermometer to monitor the soil temperature at
the planting depth while the seeds are germinating.  Keeping the soil near the optimal
germination temp. for the crop will mean more seeds will germinate.  I have a long stem
compost thermometer I use for compost and soil.  Adding more water will cool the soil and
removing the shade will warm it, obviously.

With broccoli, you may need to keep the soil temperature down while it's growing to keep
the stress on the plants down.  Stress will stimulate the plants to start going to seed
before they have grown large, resulting in small heads.  You can do this by keeping the
soil moist, but not soggy- it takes more energy to heat water than dry soil.  Also, using
a mulch to shade the soil will help keep the temps down and will have the added benefit
of conserving soil moisture.

Good luck!

Alex McGregor
Walden Farm

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