How to Grow and Care for Hybrid Primrose (Polyantha Primrose)

Garden primroses comprise several species in the Primula genus, a group of spring-blooming perennials with blossoms in various shades of purple, red, yellow, and pink, depending on the variety. The type most often planted in garden cultivation are hybrids and their cultivars, most of them derived by crossing P. vulgaris and P. veris. These hybrids are given the name Primula x polyanthus, polyantha primrose, or simply primrose. Along with their use in the garden, they are commonly used as short-lived houseplants. They have deep green crinkled leaves that form a low clump with bright, dish-shaped flowers.

This is a somewhat finicky, slow-growing plant species that is usually purchased as a mature nursery specimen. Spring is usually when garden centers offer potted specimens, either already flowering or about to bloom. If you're planting primrose from seeds or from divisions, you may wait a full year (or as much as three years) for the plants to reach flowering maturity.

Keep in mind that primrose is toxic to humans and pets. Place your plant out of the reach of children and animals.

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Primrose Care

Caring for primrose plants outdoors requires just the right combination of sunlight (bright but indirect), water (evenly moist), and food (immediately after planting) in order to produce healthy plants. When grown as garden plants, they like some full sun in the morning but shade as the day heats up.

For indoor use, primroses are often sold with the expectation of growing them temporarily, then discarding them after they are finished flowering. It is sometimes possible to nurture them into repeated blooming, but this is difficult. For the most part, you should not expect a long-lived houseplant. Primroses do well indoors for a short period of time, but will not survive long-term inside.

Primroses last for about six months indoors, while their flowers last for several weeks. Extend the flowering season by deadheading primrose flowers when they die off. When your primroses finish flowering, consider moving them outside. This may coax them into rebloom late in the season.

Keep these plants in a good balance of conditions; successfully growing primrose plants is largely a matter of temperance and moderation.

Light

Primroses can like either sun or shade depending on where they're growing; when grown indoors, these plants prefer brightly lit windowsills, but they should not be exposed to direct sunlight. When planting primroses outside, put them in a spot that's mostly shady, but that receives some morning sun.

Soil

These plants need a loose, well-drained, very rich potting mix with a high level of humus. Most general-purpose potting soils based on peat moss provide this. You can make your own potting mix with even proportions of peat moss, vermiculite, and perlite. This mixture not only holds moisture well but also offers very good drainage.

In the garden, primroses prefer a rich, well-draining soil that is slightly acidic.

Water

Primrose needs 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 and adjust watering accordingly.

When growing primroses inside, do not overwater. Too much water is an invitation for root rot or lethal fungal infections. Wilting, even though the plant is getting water, is a sign of root rot.

Temperature and Humidity

Primroses do best in moderate to cool temperatures—intense heat can cause wilting and plant failure. They grow best at temperatures between 50 and 65 degrees Fahrenheit, and they genuinely resent temperatures above 80 degrees Fahrenheit. Primrose likes high humidity, which can be provided through the use of a humidifier or by setting the pot in a saucer filled with pebbles and water.

Fertilizer

Feed your primrose plants with a weak liquid fertilizer at the start of the flowering period. For the amount to use, follow product label instructions. 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.

Types of Primrose

For indoor growing, the best primroses are cultivars of P. polyanthus, but there are also cultivars of P. auricula that make for good houseplants. Some notable varieties include:

• 'Belarina Colbalt Blue': This 5- to 8-inch plant has rich, blue double flowers that bloom profusely. It is a favorite for growing in pots and makes a good garden plant in zones 4 to 8.
• 'Belarina Nectarine': This cultivar has large, fragrant, golden yellow flowers.
• 'Zebra Blue': This variety has extra-large flowers with striped blue and white petals. It is especially long-blooming as a houseplant, flowering from late winter to spring.
• 'Crescendo Bright Red ': This variety has dramatic flowers that are red with yellow centers. Outdoors, it is suitable for zones 5 to 8. The 'Crescendo' varieties also offer other colors, including bright blue.
• 'Romance': This hybrid has very large double flowers in bright pink. The flowers are edged with thin ribbons of white.
• Primula auricula 'Cinnamon': Auricula is a species native to the rocky mountains of Europe. The 'Cinnamon' cultivar has fully double flowers in a copper-orange color. Outdoors, auricula plants can be grown in zones 3 to 8.
• Primula aricula 'Larry': This cultivar has rich purple flowers with lilac petals and white centers. The auricula cultivars are known for having dramatic two-tone and three-tone flowers. Other cultivars include 'Blue Velvet', 'Dale's Red', 'Harry Hotspur', and 'Sirius'.

Propagating Primrose

Although the technique is more often used for primroses planted in the garden, division of the root clumps can also be used to propagate more plants from an indoor specimen. This is best done after the plant is finished blooming (when they are often discarded anyway). Here's how:

1. Remove the entire plant from the pot.
2. Carefully divide it into quarters, making sure each division has both leaves and a good body of roots.
3. Immediately replant the divisions into their own pots filled with fresh potting soil or a mixture of peat moss, perlite, and vermiculite.

You can expect the new divisions to take a full year before they flower. Their slow-growing, finicky nature is why primroses are usually purchased as near-mature nursery plants.

How to Grow Primrose From Seed

Though usually planted from nursery-grown plants, primrose can be grown from seed, though this is a challenging activity. Expect to lose some seedlings, and don't feel too bad if your experiment fails. Moreover, they can take quite some time to mature into flowering plants—some varieties as long as three years.

But it can still be a worthwhile activity for the sheer challenge of it. And for rare varieties, it may be the only way to grow those plants. However, it is not a method well-suited for beginners looking for quick results.

1. Use a mixture of sphagnum moss and vermiculite in seed trays, and soak it well with water before sowing seeds.
2. Sprinkle the tiny seeds over the surface of the potting mix, then just barely cover them with a sprinkling of vermiculite.
3. Place the tray in a relatively cool area with bright indirect light and keep them moist by misting. In a few weeks, they may sprout. Germination rates can be uneven, however, so don't be too disappointed over the relatively low percentage of success.
4. As they grow, thin the seedlings to retain those that are most vigorous.
5. The seedlings can be transplanted into individual pots when they have four true leaves.

Seedlings are susceptible to damping-off fungus, which can be minimized by maintaining good air circulation. Some growers like to spread a thin layer of fungicide powder over the surface of the seedling trays to prevent fungal infection.

As you grow them in individual pots, give primroses relatively low temperatures and bright, indirect light. Keep them moist but not wet. The seedlings will be slow-growing, so expect to nurture them for at least a full year (and possibly as many as three years) before they reach flowering maturity.

Potting and Repotting Primrose

It's unlikely you'll be repotting your potted primrose since these are generally grown for a fairly short time before being discarded. If you do, make sure not to bury them too deep, as this is a prime reason that primroses die. Pot 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 primrose plant.

Overwintering

If you are growing them within their hardiness range, leave in-ground primrose plants standing in the garden as the cold weather moves in. After the ground freezes, cover them with straw, leaves, or evergreen boughs for some protection from snow.

Common Pests and Plant Diseases

Primrose is fairly trouble-free when planted outdoors in conditions that are exactly to the plant's liking. As potted indoor plants, however, they can be subject to botrytis gray mold, which often occurs in the winter months when the plants are overwatered. Make sure to remove dead or diseased leaves to remove fungal spores. A fungicide powder may prevent the disease.

How to Get Primrose to Bloom

The normal bloom period for a hybrid primrose is spring, but be aware that garden center plants are often forced into seasonal bloom by growing them under carefully controlled lighting. If your indoor primrose manages to survive for more than a year, you can expect it to revert to its normal spring blooming pattern.

Primroses sometimes fail to bloom when conditions are too warm. Temperatures above 80 degrees usually prevent the plants from flowering.

Common Problems With Primrose

Homeowners unaccustomed to the temporary nature of this plant are often dismayed and disappointed when the beautiful flowering plant they brought home from the garden center begins to dry up and turn brown after a couple of months. Unfortunately, this is fairly normal for hybrid primroses, which are bred for a short, spectacular life. At most, a hybrid primrose in the garden might last five years, but because the flowering specimens sold in garden centers are already mature plants, it's rare for them to last more than a season or two once you bring them home.