This is something that I learned the hard way. If you decide to work with species or near species seedlings, take extra precautions with your labeling as these may send out suckers that appear quite a distance away right where you have another (and possibly less vigorous) seedling growing. It is not always possible to recognize what is a sucker from a neighboring plant especially with seedlings as you do not know for sure what a particular cross will look like.
Right now I use 3 checks - 1) I enter the name (and growing characteristics, as they appear) into a "map of that particular bed in my notebook; 2) I put a circle around the seedling made out of plastic black Gutter Guard. A name tag is attached to the top of the Gutter Guard; and 3) a plastic coated steel pole is placed right behind the plant. A name tag is attached to the top of the pole (at my age I prefer not bending whenever possible).
Leaves are not always sufficient to determine if part of a bush is from a sucker. Comparing the time and appearance of the flowers has been very useful as has been looking at the characteristics of the hips.
Why am I mentioning this today? Today I found that what I thought was a large Darlow’s Enigma seedling turned out to be a combination of the Darlow’s Enigma and a nearby open pollinated seedling of R. Brunonii (R. Moschata Nepalensis). This particular bush had 2 different types of hips on it.