I'm in the same boat.
I have to feed with some synth nutes while I'm waiting for my organic soil to finish, after that it will be organic all the way.
If I adequately flush the plants before I transplant them into the organic soil will I be ok or will the chems have a continuing negative effect on the rhizosphere?
I agree with foreverflyhi and disagree at the same time, KegBert. The ideal of using organics is twofold: One part reducing the external negative impacts on nature through using non-petroleum/nitrate based chemical nutrients, the latter reason being improving the quality and safety of cannabis plants for various sorts of healthy human consumption. So on the one hand, ethically, a person is not exactly in line with the organic community by employing a sort of hybrid synthetic-to-organic system. In addition, you will not be able to personally certify to yourself that your cannabis product is totally organic. Formalities aside, whoopty-doo.
Again, if you can start organically, just go ahead and start organically. I agree... But in our case, we have leftover synthetic nutes that we're not going to simply waste. So, yes. I'm going to veg. my plants using the synthetic nutrients that I have left. And while I would never be able to certify my product as organic, I can certainly certify to myself that my plants are organic enough for my own personal satisfaction. I mean, the alternative for us is to use what we have and go 100% synthetic (or to just simply throw away our synthetic nutes... Yeah, right). So how would it represent a service to myself and the greater organic community if I chose not to atleast try to grow halfway organic? It wouldn't.
As a matter of fact, I've amended the method I suggested from the other day, and you may want to consider it in your grows as well, KegBert. So, I'm going to take my plants from solo-to 1gal-to 3/5gal smart pots using synthetic nutrients. Then, as I eluded to before, I'm going to totally flush the salts out of the medium by running bathwater through them for 15 straight minutes or until the runoff is barely colored. From there and after the medium drys out for maybe 2 or 3 days, I will begin to feed the plants an organic tea until I'm sure they have acclimated to organic feeding - that may take 1 to 2 weeks I'm estimating. And finally, I'm going to transplant them into maybe 15 or 30 gallon pots. Those pots will be filled with healthy organic potting soil (amended with only perlite) in the upper transplant layer, and then a super compost in the lower layer of the container. From there, I'm going to allow them to veg. another month before flowering.
Using this method? I will be satisfied that my cannabis product is thoroughly organic. Again, for certification purposes, it would not be considered "organic". But in reality, the finished product will be all but 100% organic.