Primroses are often seen as harbingers of spring, providing long weeks of bright, colorful blooms in the garden as well as container planters and hanging baskets. Polyanthus is a low grower, forming a large rosette that sports multiple blooms on short stems, and tolerates full sun until the temperatures start to rise in the summer. Take care not to cover the crown of a primrose with soil, as that may cause it to rot. Technically a perennial, primroses are often treated as annuals, as they tend to suffer in extreme heat.