Native milkweed plants are adapted to your particular climate and will require less care and maintenance. For example, a non-native species may require additional watering because it is not adapted to California's drier or sunnier weather. In another example, a recent study indicated that hotter weather can cause tropical milkweed to produce excess levels of cardenolides that are actually poisonous to monarch larvae and caterpillars.

Planting non-native milkweed may cause changes in monarch butterfly behavior. For example, non-native milkweed may have different characteristics at different time periods from native milkweed. Some studies suggest that the different blooming times, or the evergreen nature of some milkweeds, may confuse monarch butterflies to begin mating and laying their eggs in the wrong season.

Planting non-native milkweed may cause, changes in monarch butterfly migration patterns. For example, unlike narrow-leaf milkweed (which becomes dormant during the winter), tropical milkweed stays green throughout the year. Some monarch butterflies may end up staying in the area where they discovered the tropical milkweed instead of continuing on in their migrations.

Non-native milkweed species such as tropical milkweed are more likely to host parasites such as OE and significantly increase the risk of infection for monarch butterflies.