I get asked this questions almost daily and sometimes more than once a day. I’m going to post a recent reply that I sent a customer when they asked if they have to worry about cross pollination between multiple varieties of alpine strawberries that they purchased and others asked if the alpines will cross pollinate with garden variety hybrids. It also applied to other species of strawberries like musks and virginia strawberries. All strawberries are in the genus Fragaria. Alpines are the species vesca; Musks are species moschata; virginia strawberries are species virginiana. Garden hybrids are species X (mean cross) ananassa.
Alpine strawberries are self pollinating aided by wind and insects. Mixed alpine varieties will cross. There is no getting around that unless each variety is isolated from the other. Isolation can be done with physical isolation (space between beds) or caging of each variety to eliminate cross pollination due to wind and insects. If one is saving seed and wants it to be true to the cultivar (variety) then isolation is a must.
The crossing doesn’t effect the flavor of the current crop of berries. What you will find in a mixed planting over time is that unpicked berries will fall to the ground and reseed. The seed from these berries is a genetic mix and may result in a varieties with new characteristics including runnering, different colored fruit, even different plant growth habits, etc. There is no way to predict what will result.
Many years ago I had a half barrel of ‘Rugen’ and a half barrel of ‘Yellow Wonder’ next to each other. In the third year I started noticing white berries in the barrel that should have had reds. It took a while to figure out what had happened. I initially thought the reds had reverted if there is such a thing. Some scientist, huh?
Usually, by the time this mixing happens the plants are overcrowded and ready for renovation. The soil is exhausted and little organic matter remains in the container. Renovation usually is done by dividing the plants and replanting into the same or other beds. The need for renovation depends largely on how well the bed was maintained. If most fruit is picked then there will be less “genetic contamination”.
As an extra point, crossing between species is not common for most species in nature. You don’t have to worry about alpines crossing with garden hybrids or wild plants of another species. Of course, there is always the chance that this would occur so it’s best to isolate from other species if you want absolutely no crossing. On the plus side, if you like to play the lottery, the cross between species could be the next million dollar variety!