question about non-native plants and pollinators

**C* U* <c*@gmail.com>**

I'm well aware of the importance of growing native plants in order to benefit pollinating birds and insects. But I also see in my garden that certain non-natives attract bees and other insects.  Nepeta, calamintha and Allium 'Spring Beauty' attract bees in droves, and the nepeta is particuarly valuable, it seems to me, because it gives the bees something to eat in May when Joe Pye weed, cultiver's root, echinacea, milkweeds, anise hyssop and ironweed are still weeks away from blooming.  I have Penstemon digitalis, which the bees like in May, but they also like nepeta at that time, and it seems to me that they need the nepeta. 

Should I not grow crocus? At the end of March, when the snow crocus open, I always see some bees hovering above them. If I didn't have the crocus, what would these bees be able to feed on?

So is there any "harm" in growing these non-natives?  Does the pollen from these and other non-natives negatively affect the ecosystem in some way? I'd like to contact someone who can speak authoritatively on this topic and not polemically. 

Carolyn Ulrich
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