Could always get you trays up and running... let whatever you have germinate... then remove it all. Then plant you chives.

My mother used to use garden soil to start her seeds but she baked it at about 200 degrees IIRC for a while. Sorta stank up the place but then she had sterile planting soil, too.

If you have weed seed in a commercial mix, it is time to switch brands, IMO. You should not have weeds of any kind sprouting in commercial seed starting media even without cooking the mixture.

If you mix your own use sterile components.

I like Nevermore44's idea. Just let them sprout, kill them and move on.

Thanks for the responses. However, if all the weeds would sprout at the beginning there would be no problem. The problem is the weeds keep sprouting for years.

If that's the case... you should switch brands like OldDutch notes. Any seed starting mix should be fairly sterile and not contain weeds to any appreciable level.

Any suggestions for a weed free brand? I usually use Lambert's, which has Canadian peat, which is where the weed seeds come from.

Do you have your pots outside? Maybe seeds are blowing in, or being dropped by birds. I shouldn't think they would wait all that long to sprout if they are in there to begin with.

I doubt it is the peat that is a concern. Virtually ALL commercial potting mixes are peat based and few develop any sort of weed issues. Peat on its own is not a very viable base for weed seeds (far too acidic for most) and is harvested from areas were few weeds appear naturally anyway.

Most commercial seed starting mixes are sterilized, both to avoid any weed issues and to reduce the issues with damping off and other early seed fungal problems. Just find another seed starting mix that has been properly sterilized or make you own.

I use pure peat from the giant blocks (plus sand or pine needles) to start sarracenia (pitcher plants) indoors. That peat, which isn’t sterilized, does actually grow a decent amount of grasses and or sedges. Maybe that brand just isn’t sterilizing their product enough. I would just try a different brand and see what happens. As noted most mixes are a majority peat based. Or you instead try out the coir based mixes or compressed blocks and avoid peat all together.

Pro-Mix is my favorite.

Nevermore, was yours Canadian sphagnum peat or was it a more local reed sedge peat? Two very different products and the reed sedge peat (harvested and sold in various parts of the US) would be far more likely to include weed seeds. I have never known true sphagnum peat to include any weeds or weed seeds.

All Canadian. I start the tray inside for the sarracenia, so no contamination from the outside. I will say that the weeds take a while to get growing. The don't start up immediately.

I went completely over to coir. Last spring I mulched my garlics with about 2" of coir mixed 50/50 with sterile compost and then topped that with two more inches of leaves from the previous fall. I completely avoided having to weed my garlics last summer. Not a weed got through. Hopefully I can repeat that this coming year. I like coir and it is sterile and competely renewable, which peat and sphagnum are proving not to be.

NHBabs That sounds like a good possibility. How long in the microwave? I have been thinking about well-dampened mix in the gas grill till it hits 250 degrees.

Sounds reasonable to me, though it doesn’t need to be that hot; I think something like 180-190 degrees should do it. That would take care of the issue of indoor stink. I did it until it was steaming. You could also try using a metal pan on the grill.

If it takes a compost pile a couple of hours at 140-150 degrees, baking to reach 180 should do the job nicely. Remember the temps it takes to make meat safe to eat. Those would also kill weed seeds.

I think there are some seeds that are heat resistant. Some require high heat, as in a fire, to germinate. That is why I am thinking heat high enough to cook the seeds - not just to sterilize the mix.