Of course you can check! But don't be tempted to peek before twenty or more days. If you are using a heat mat to provide bottom heat, the seeds will germinate much more quickly. Verbena seeds can take forever to germinate, weeks and weeks. I've actually never seen a black plastic recommendation before. Usually, a covering of fluffy germination mix is all that is required for seeds that require darkness and that's all I've ever done as a professional or a retired hobbyist. I'd think that covering with black plastic would encourage mold and mildew and set the seedlings up for rampant damping off diseases after germination. Anyway, I'm not going to confuse you by telling you how I would do it, but just ease your mind about checking for germination. Be very careful that the medium is not overly moist when you cover it or your project will not be successful.

I also germinate with plastic covering. I do not put them in any light at all until I remove the plastic. They would likely cook.

Thank you Kara and Stefan! Here's my set up: I have the seeds in a little container of mixed cactus soil and perlite and covered with plastic wrap, keeping them moist but not soaked. I've been checking to make sure they arent getting moldy and dont have the plastic 100% sealed, so there is a small amount of air flow. Placed in a large east facing window that gets direct morning sun and is pretty bright all day. I have many different cacti and succulents in that window and they are all thriving. Did the same seed germination set up with the Euphorbia obesa and Adenium obesum seeds and those are growing well so far. I wont give up hope yet, thank you for letting me know that some take longer. And I guess if it doesnt work out with these seeds, I'll keep trying! :-)

I am surprised someone wants to grow mugwort (wormwood) - it is a constant battle keeping it out of my garden beds. But, because of that I have become educated on mugwort propagation, and they usually don't grow from seeds. They sprout from rhizomes that form on the roots - which makes them so difficult to control. If you leave any of those little rhizomes when you pull them out, you will just have more in a few weeks. I'm sure they can be grown from seeds, but the seeds don't need a high germination rate because the plant can spread just fine without them. I would see if someone sells the rhizomes and try that instead of seeds. Or find someone that already has a mugwort plant and get a few rhizomes from that.