there's info here about chamomile and tansy
http://forum.grasscity.com/organic-growing/1233246-new-companion-planting-w-cannabis.html
it is my opinion that the avg. time growing (60-80 days) just isn't long enough to warrant it.
chamomile is said to be ready in 30days but why would i want additional roots sucking nutes from my mj.also there's maintaining the herbs height might make the benefits not worth it unless you let them grow natural where they get big and start shading the mj plant. it's a fascinating concept, symbiotic plant systems, but so far all i see worth it is the mycorhizae. also marigold is used. if i had plans to do a long term grow i would use white clover. benefits, somewhat shallow roots, can pack an insane amount in a small space and it would be cool to look for 4 leaf clovers while checking your plants. i buy white clover seed buy the pound, they germ fast and stay low so no worry about pruning or shading.transplanting will pretty much ruin them though.