Polyanthus plants, commonly known as primrose, are a spring plant that offers blooms in a rainbow of colours. A wide variety of species thrive in different growing conditions; you should be able to find a polyanthus species for your gardening needs, whether it is a rock garden, meadow or more conventional garden. No matter the variety, all polyanthus must be grown in cooler weather.
In the Ground
Polyanthus can be grown from seed, but the germination time is four to eight weeks, and it will be several months before the plant will bloom. Most gardeners prefer to purchase their primrose plants from nurseries or garden centres, where the plants have already developed a bud, or are already blooming. Primrose has a long blooming time, so buying plants that are in bloom will not mean a shorter enjoyment of blossom colour in your garden. Polyanthus thrive in nighttime temperature from 10.0 to 15.5 degrees C, and daytime temperatures that remain under 29.4 degrees C. English primrose is one of the most popular polyanthus species in gardens. This species requires a partially-shaded location with well draining, rich humus soil. Add compost to your soil to create a more humus-rich condition. Water the soil to maintain moistness, but do not let the ground get waterlogged. Polyanthus do not require additional fertiliser, and are seldom bothered by pests or diseases. Although polyanthus is a perennial, many gardeners treat it as an annual and remove the plants from the garden after the blooming season to make room for summer blooming plants. Larger, established polyanthus plants can be divided and replanted after blooming if planted in a shaded area to avoid summer heat.
Polyanthus plants are wonderful in containers during the spring. Plant them the same as you would in the ground, with well-draining, rich humus soil. When the weather is cool, the containers can be in full sun, but as the temperature warms up, move the container to a partially-shaded area to extend the blooming time. Spring-blooming bulbs, such as daffodils and tulips, are often planted with primrose in containers.
In very cold regions where a splash of bright, vibrant-coloured blossoms would bring cheer to cold winter days, grow polyanthus indoors. As long as the plant has bright light, but not direct sunlight, is kept in a cool spot away from heat sources, and you keep the soil evenly moist but avoid waterlogging the roots, a polyanthus plant will do fine inside. After the frost, move the plant outdoors in its original container, or transplant it to a new container, or into the ground.