The Primula genus contains at least 500 species and an almost infinite number of hybrids and cultivars. Most are short-lived perennials. Cultivated varieties usually carry the common name of primrose, and they generally share a similar shape—low rosettes of dark green leaves with umbrels of colorful flowers that arise on sturdy stalks in spring. There's a lot of diversity in primrose flowers. Some have clusters of flowers on a single stem, while other primulas have one flower per stem, with stems that create clusters of flowers that skim the rosette of leaves. They may remain evergreen in the zones where they are hardy.
Primrose is toxic to humans and pets.
|Common Name||Primrose, polyanthus|
|Botanical Name||Primula spp.|
|Plant Type||Perennial, annual|
|Mature Size||6–20 in. tall, 8–20 in. wide|
|Sun Exposure||Partial, shade|
|Soil Type||Moist, well-drained|
|Flower Color||Red, pink, orange, yellow, blue, purple, white|
|Hardiness Zones||3-8 (USDA)|
|Native Area||North America, South America, Europe|
|Toxicity||Toxic to people and pets|
Primroses thrive in partial shade and look perfectly at home when planted in large swaths near a tree. Some varieties can tolerate full sun, but they'll need more frequent watering to remain cool and moist. Most prefer part-shade to thrive. To guarantee you get the flower color and style you want, buy your primroses while they are in bloom. They should remain in bloom for several weeks after you take them home and plant them.
Once established, primroses need very little care, other than occasionally dividing the expanding clumps if you are growing them as perennials. Just be sure they get regular water, which shouldn't be a problem in the spring, and some shade during the hottest hours of the day. If you plant them in a suitable site, you should not have problems. They don't even require winter protection.
The hybrid primroses prefer a partial shade location where they experience some morning sun but shade during the heat of the day. Species types, such as P. vulgaris, do a bit better with full shade.
As woodland plants, primroses prefer moist soil with a slightly acidic soil pH. They also welcome copious amounts of organic matter. While primrose plants like moist soil, most varieties do not like to sit in wet soil and need the well-draining texture that a rich, organic soil can provide. (Both Primula japonica and Primula denticulata can handle wet feet.)
Hybrid primroses are fairly thirsty plants and require regular watering. A good layer of mulch will help retain soil moisture, but they do not like to be constantly soggy. Species types are somewhat more tolerant of wet soils.
Temperature and Humidity
Hybrid primroses are hardy in zones 5 to 7 but are often grown as bedding annuals in warmer and colder zones. Some species types are hardy as far north as zone 2. But no primroses are suitable for USDA Zones above 9 and up because they require a winter chill to survive and bloom.
Hybrid primroses need regular feeding with a half-strength liquid fertilizer—a requirement that's common with profusely flowering plants. Species types can be over-fed, however, and do well with just a single spring feeding.
Types of Primrose
There are several excellent varieties of primrose, including:
- Primula x polyantha : These are the modern hybrid primroses, offering many different bright colors. Most garden center primroses are of this type. They are quite easy to grow. They are hardy in zones 5 to 7, but often grown as annuals elsewhere.
- Primula vulgaris: This is the common wild primrose that is native in most of western and central Europe. It has pale yellow flowers that bloom in April. It is not a common garden plant, but it serves as one of the parent species of the many hybrid primroses. It is hardy in zones 4 to 8.
- Primula denticulata (drumstick primrose): This plant is native to the Himalayas and is hardy in zones 2 to 8. It grows about 1 foot high with a clustered ball of flowers atop a sturdy, upright stem.
- Primula veris (cowslip): This yellow-flowering Primula is native to Europe and Asia but has now naturalized over much of eastern North America. It is hardy in zones 3 to 8.
- Primula kisoana (hardy primrose): Hardy in zones 4 to 8, this species has striking pink to mauve flowers that bloom from April to May.
- Primula japonica (Japanese primrose): This is an excellent species for planting around water features, as it thrives in a moist environment. Growing 1 to 2 feet tall, it blooms with white, pink, purple, or red flowers in late spring and early summer. It is hardy in zones 4 to 8.
It's easy enough to lift and divide primrose plants after flowering. This is the best way to multiply your batch since it guarantees you can maintain specific cultivars.
- Lift the entire plant out of the ground with a shovel. Divide it in half or more sections using pruners or a spade.
- Replant each in a new location and keep it well-watered until you see new growth in a few weeks.
How To Grow Primrose From Seed
When starting plants from seed, a temperature between 40 and 50 degrees Fahrenheit is required from sowing to first bloom, which is next to impossible to attain indoors. Growing primroses from seeds is a tricky business that is usually discouraged.
Potting and Repotting Primrose
Primroses purchased as potted houseplants that are forced for early blooming can be kept growing almost indefinitely, moved outdoors during summer, and back indoors for winter. However, they will soon revert to their normal flowering rhythm, which is to bloom in early spring.
Plants can quickly become root-bound unless they are divided or potted up annually into larger pots. Use a standard commercial potting mix when growing primrose in pots, making sure the pots have good drainage. Regular repotting can also prevent excessive fertilizer buildup that can ruin plants.
Depending on the hardiness of the cultivar, many of these hardy plants don't need any special care for overwintering. For more tender varieties, adding mulch or evergreen boughs around the plants can add protection.
Common Pests and Plant Diseases
Primroses are generally pest-free, but spider mites can be occasional problems, especially when the plants are heat-stressed. Less frequently, plants may be troubled by mealybugs, aphids, and whiteflies; they are best treated with non-chemical remedies, such as horticultural oils.
Primroses are also prone to a leaf spot disease, which manifests as brown lesions on yellowing leaves. Remove infected leaves and make sure your plants are getting adequate air circulation.
How to Get Primroses to Bloom
Primroses prefer a temperature of between 50- and 60-degrees Fahrenheit at night, as well as a temperature of lower than 80 degrees Fahrenheit during the day, so keep indoor plants in a cool area of your home. Make sure the light the plant gets is indirect, never direct, as this can heat the plant too much.
Keep in mind that though a primrose might have been forced to bloom for the nursery or as a gift plant, it will eventually revert to the natural blooming cycle, which is for about six weeks in the early spring.
What are good companion plants for primroses?
How long does a primrose plant live?
Primrose can live for up to five years when given the proper conditions.
Where should I place primroses in my house?
Your primrose plant needs bright but indirect sunlight. A bright windowsill on a northern-facing exposure is a perfect spot.
Toxic Plants. University of California.