Tuesday, November 29, 2016

Dealing with Weed Seeds in Compost

This accidentally turned into a nice demonstration because the various leafy greens germinated in their soil blocks at different times and were planted out at intervals of a few days.

My compost method is known as "slow" or "cold" composting.  This pile it and forget it method doesn't produce enough heat to reliably kill weed seeds.  Some will die of old age before the compost is used, but others will survive.

That means my just-filled raised beds were filled with unsprouted weed seeds. They sprouted as soon as they got  light and moisture, leaving me with a weedy mess of a vegetable bed like this. 
Weedy mess and transplanted chard seedlings
It will get worse every day unless ...
I water the soil, let the weeds sprout, then rake the soil a couple of times to kill most of them before I plant more vegetables. 

The raised bed was filled with sifted compost, mixed into the sandy dirt underneath and soaked thoroughly several times while the seeds were in the workshop germinating.

After I planted out the chard seedlings in soil blocks, the bed erupted with hordes of tiny weedlings.  The part with the chard will have to be hand-pulled when the weedlings are big enough because I (foolishly) planted them too close together for even my smallest rake or hoe.

I raked the remaining part of the bed to disrupt the tender weedling roots before setting out  some lettuce seedlings in soil blocks.  There are significantly fewer weeds.
Not so weedy, raked once, with lettuce seedlings.
The bronze leaves of the lettuce is hard to see.
I raked the empty part of the bed one more time, after planting the lettuce, and the supply of weedlings seems to have exhausted itself.
Raked three times, very few weeds.
The first conclusion from this unplanned experiment is that you should soak your freshly amended area thoroughly, keep it moist until the weeds erupt, then kill them by raking the surface.  Keep it moist for a week or two, raking new weeds out of the soil as they appear, then set out your vegetables.

The second conclusion is that you should never plant things any closer than the width of your smallest rake or cultivator.   I'm still hand-pulling weeds out of the chard.

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