Normally thought of as outdoor plants, Primulas are excellent indoor potted plants for winter or spring blooms. Although the Common Primrose (Primula vulgaris) can be grown as a potted plant inside, the favorite potted Primulas tend to be the more delicate species, with clusters of small blooms that rise above the crinkled and attractive leaves.
All delicate Primula should be treated about the same, and in no case should you expect a long-lived houseplant. Instead, think of your pot of spring-time Primula like your blooming fall Phalaenopsis Orchid: it's a beautiful visitor, but will not survive over the long term inside. Once the plant has finished blooming, you can move it outside to a protected spot of your summer garden and hopefully enjoy a season of additional blooms.
Light: They prefer brightly lit windowsills, but the fancy indoor plant should not be exposed to direct sunlight. When planting them outside, put in a shady or dappled corner.
Water: Primulas need adequate, even, and regular moisture to thrive. They shouldn't be soggy, but don't let the soil dry out either. Look for signs of wilting.
Temperature: Moderate to cool. Intense heat can cause wilting and plant failure.
Soil: A loose, very well-drained, very rich potting mix.
Fertilizer: Fertilize with a weak liquid fertilizer during growth and flowering. Because these are not meant to be long-lived indoor plants, a single application of controlled-release fertilizer may be adequate to get them through the flowering season.
It's unlikely you'll be repotting your potted Primula. If you do, make sure not to bury them too deep—burying too deep is a prime reason Primula succumb. Bury the plants, so the top of the root ball is slightly elevated above the level of the surrounding soil. Never pile soil up around the stem of a flowering plant.
They are propagated from seeds, which are sown directly in soil or potting media. Most pots of indoors Primula are purchased as flowering plants, destined to be set atop a desk, sill, or table until they're done flowering. However, if you're interested in selecting and starting your own Primula pots, sow seeds directly into the pot in fall or early winter and keep the seedlings under fluorescent lights in a warm spot, with regular water. Plants should be blooming by early spring.
Potted indoor Primulas are a delightful way to usher out winter or welcome in the spring. They are available in a wide range of striking colors, forming a mass of flowers. Most people prefer the taller, upright delicate Primulas indoors, but even a pot of common Primula is an excellent addition. Extend the flowering season by pinching off dying buds. After the plant has done blooming, consider moving it outside. While inside, do not overwater; wilting even though the plant is getting water is a sign of root rot.