Hello Cindy,
Phytates, also known as phytic acid, is the principle form of phosphorous storage in many plants.
While it is quite true that phytates can "bind up nutrition" you need not worry about them in your greens. Phytates are mainly found in grains (seed), with the highest concentration found in the hulls.
This is the reason it is recommended that nuts and seeds be soaked (or sprouted) to neutralize the phytic acid (even cooking only slightly decreases phytic acid). Fermentation also can neutralize phytic acid.
Would you please include where you read about phytates in greens? - I love learning more. As far as I know you can continue drinking your green smoothies worry free of phytates (unless you include seeds/nuts in which case you should soak, sprout or ferment first).
Enjoy your raw greens!
John