As for evasion with some +1/+1 counters on it, consider the old scrappy Plaxcaster Frogling. It's full of drawbacks: the evasion provided isn't that cheap and it's not "hexproof-" but "shroud-like" : (But the Graft 3 has ok synergy with Hardened scales and even though it has its costs, it manages to provide some evasion to targeted removals.

Lasty, if you prefer to keep the Geists (as they're good) it's possible that you have more to gain by having them keep their "undying"; if that is the case you might want to consider having easy access to something that renews their undying quickly and consistently by removing a +1/+1 counter from them. In addition to the instants you have (Bioshift, Fate Transfer) there's the possibility of using Scarscale Ritual but I'd suggest something that's reusable to remove those unwanted +1/+1 counters: what comes to mind is Simic Guildmage, Zameck Guildmage, Sage of Fables, Ooze Flux.

No problem, I've done the same thing. :)

I should note that I have a BG version of this deck that I find to be more effective/enjoyable, so I haven't worked on this one in a couple months. That said, reading your suggestions I had some thoughts to myself like, "What? Why do I have 4 Strangleroot Geists?" and "Why is Bioshift in my sideboard?" I did consider Ring of Kalonia, and both the rings are probably worth testing. I'm not sure how I missed Simic Guildmage, as that would be pretty effective in my BG deck (which contains the similar Cytoplast Root-Kin, pairing beautifully with Protean Hydra).

I play pretty casually, so I'm not super concerned about removal, but I agree that I do need some sort of answer to it.

Thanks!

Wow that BG list is the casual Hammer! Thanks for linking it!!!

Young Wolf + Strangleroot Geist have nasty interactions with Hardened Scales.

Strangleroot Geist is already in there, though only two of them. I considered Young Wolf for a while, but I feel Experiment One is a more effective 1-drop here and to put Wolf in over anything else would reduce the likelihood of triggering evolve (at least on initial casting).

While undying is great, it requires the creature dies to get the counter(s), and as someone above pointed out, without a way to remove the counters it's not as great. However, my BG counter deck (which I must say is much better) definitely involves the element of moving counters around. If you're interested: http://tappedout.net/mtg-decks/counters-on-all-the-things-turn-4-win/