Great question, Rod. If you're using Seventh Generation Detergents, you can use the greywater for your plants. Check out the specific product links below to find the products you're using, and see the features and benefits section, which specifically calls out the greywater and septic safety.

Laundry:
http://www.seventhgeneration.com/Laundry-Detergents

Dishwashing:
http://www.seventhgeneration.com/Dishwasher-Detergent

I also found a few very helpful sites on Greywater usage (see the links below), which talk about the many benefits of using Greywater, as well as specific usages and recommendations.

http://www.greywaterguerrillas.com/greywater.html

http://www.oasisdesign.net/greywater/

I hope this was helpful! From what I've read, it sounds like the greywater can be really beneficial for plants because of the compostable waste present in the water. Interesting stuff!