2. Understand Your Variety
There are more than 100 different varieties of petunia out there, and they come in a variety of different shades and types. The first thing that you should know about petunias if you’re a novice gardener who has never planted them before is the fact that there aren’t too many differences between the varying types of petunias – but you should still get to know which variety you have before you plant it just in case.
Some varieties of petunias will grow outwards far more than other, smaller varieties and this is one thing you’ll have to compensate for when planting. As a rule, petunias shouldn’t be spaced too close together – but too far apart and you’ll end up having “gaps” in what should have been a solid row of flowers.
Do your research on which variety of petunias you have before planting them and it can save you a considerable amount of wondering about what goes where later on.