The primrose is one of 4 similar primula species we have in the UK. The others are Cowslip, Oxlip and False Oxlip.
Primroses are what you are most likely to see and are out now (March) and continue into April.
In fact with recent milder conditions they often seem to be in flower throughout the winter months.
Primroses have one flower per stalk and are primrose yellow. That is not as daft as it sounds; most people know primrose yellow even if they have not seen a primrose. Cowslips have lots of flowers per stalk, the colour is more apricot yellow and the individual flowers are quite small. Oxlips have lots of flowers per stalk, the colour is yellow, the individual flowers look like small primroses and all the flowers point in one direction. False oxlip is a hybrid between a primrose and a cowslip. It looks like an Oxlip but the flowers on top of each stalk point in every direction. They are quite uncommon. All the species in the primrose family have a clever way to prevent self pollination. The flowers are either pin eyed or thrum eyed.This is known as heterostyly. If you look at my diagram you can see the difference. Pin eyed have the stigma near the top of the petals and thrum eyed have the stamens near the top of the petals. The effect is that when pollinating insects visit the flowers they will transfer the pollen of the thrum eyed flowers to the stigma of the pin eyed flowers and visa versa. All flowers on a particular plant are of one sort. It is controlled by a group of genes which are closely linked on one chromosome so that in effect they act as one gene which is known by the letter S. If you know your genetics you will know that there are two alleles for each gene and they can be dominant or recessive. Thrum eyed has one dominant allele and one recessive so is Ss, pin eyed is SS so the pollen from the thrum eyed will be 50% S and 50% s. All the pollen from the pin eyed will be S and so when pollination occurs 50% will be Ss and 50% will be SS.
What is the point of all this? Well, it will mean a better mix of all the other genes in the plant’s offspring which means they will stand more chance of being able to colonise slightly less favourable areas or be able to fight off disease better or be able to adapt to new conditions. To use a modern phrase, they will be ‘more fit for purpose’.