When the shadows fall over the garden, the evening primrose plant unfurls its beguilingly fragrant yellow flowers.
The biennial plant has made a name for itself as an ornamental, medicinal, and food plant for generations. Learn here how to spur the plant to peak performance.
Planting Evening Primrose Properly
Plant a young evening primrose into the bed or a pot with a minimum diameter of 12 inches (30 cm) from mid-May. Choose a sunny location with well-drained, loose soil.
Commercially available potting soil is suitable as a substrate in the planter, which you can optimize with sand, perlite, or lava granules.
While you prepare the garden soil, place the potted root ball in the water.
This is how the planting proceeds:
- Dig a hole twice the size of the root ball.
- Add to the excavation a little compost with horn shavings.
- Pot up the flower, plant it in the middle and water it.
- Maintain the previous planting depth if possible.
In the container, you should put some clay shards over the water drainage holes as drainage before filling in the substrate.
Spread water- and air-permeable fleece over the clay shards, so that crumbs of soil do not immediately block the protection against waterlogging.
To provide the evening primrose with the best possible care, you want to pay attention to the following aspects:
- Water evening primrose plants only during drought.
- Start fertilizing the plant in March/April to cover its nutrient requirements.
- Fertilize freshly potted plants only from the second year every 4 weeks.
- Regularly clean out withered flowers.
- Cut off wilted flower stalks, if seeding is not desired.
- Leave the retracted foliage in place during the winter as a natural protection.
At the beginning of winter, cover the plant with a layer of leaves or brushwood. Ideally, you should move an evening primrose plant in a pot into frost-free winter quarters.
Large containers with a diameter of more than 12 inches (30 cm) can survive the cold season, if they are wrapped in foil, stand on wood, and the substrate is covered with straw or leaves.
What Kind of Location is Suitable for Evening Primrose?
In order for the evening primrose plant to enchant the garden as a summer night fragrant, it should soak up as much sun as possible during the day.
Consequently, assign it a sunny, warm, and wind-protected location. The plant anchors itself with its strong taproot within a short time in humic, sandy-loamy soil.
The Right Planting Distance for Evening Primrose
If you choose the expected growth height of the flower as the planting distance and halve this value, you do it perfectly right.
For the common evening primrose (Oenothera biennis) with a height of up to 48 inches (120 cm), the distance to the plant neighbor should thus be 24 inches (60 cm).
For smaller evening primrose varieties with a height of 24 inches (60 cm), place them at a distance of 12 inches (30 cm).
A ground-covering bigfruit evening primrose (Oenothera macrocarpa), on the other hand, goes more in width than in height. With a growth height of 10 inches (25 cm) and a growth width of 16 inches (40 cm), a planting distance of 16 inches (40 cm) is recommended in this case.
What Soil Does the Evening Primrose Need?
There is no big fuss about the soil condition. Basically, the evening primrose plant thrives in any normal garden soil that does not pose a risk of waterlogging.
Those who take it seriously settle the plant in soil that is:
- Moderately nutritious
- Humic, fresh, and well-drained
- Sandy-loamy to gravelly and calcareous
In herbaceous borders, the evening primrose plant feels just as comfortable as in the rock garden, the gravel bed, or the vegetable patch of the kitchen garden.
What is the Best Time for Planting the Evening Primrose?
A ready-bought or home-grown evening primrose plant can be planted in loose soil or in a large container from mid-May.
If you prefer direct sowing to establish the plant in the garden, the time window opens in June and is open until the end of August.
When is Flowering Time for Evening Primrose?
The flowering period of an evening primrose plant extends from June to September.
What is remarkable is not only the long duration but the timing itself. The yellow flowers open only at dusk to release their intense fragrance in the garden, swarmed by hungry night butterflies.
Pruning Evening Primrose Properly
By pruning at the right time, you’ll regulate spread, make room for young plants and bring a decorative vase ornament into your home.
Here’s how to prune the evening primrose plant properly:
- Immediately cut off wilted flower stalks to prevent seeding.
- Alternatively, cut wilted shoots in half to regulate the degree of spreading.
- Cut off the retracted foliage close to the ground only in February/March.
- Cut off blooming evening primroses at the base to use as vase decorations.
Clean out wilted flowers regularly, and the effort will be rewarded with an extra-long blooming season and a well-groomed appearance at all times for this impressive flower.
Watering Evening Primrose
Evening primroses know how to cope with short-term drought much better than with waterlogging. Therefore, water the plant only when the natural rainfall is not enough.
If the plant is in a container in a rain-protected location, check the substrate every 1-2 days. If the top inch (2-3 cm) of the soil proves to be dry, water the plant.
Fertilizing Evening Primrose Properly
The nutrient supply of an evening primrose plant in the bed is limited to a starting fertilization in March/April in the form of compost with horn shavings or a complete fertilizer.
In a pot with pre-fertilized potting soil, do not administer a liquid fertilizer until the second year. Then, starting in April, fertilize the plant at monthly intervals during the flowering period.
Gardeners often complain of powdery mildew on an evening primrose plant. This widespread fungal infection is in peak season just when the flower is at its summer peak.
But it is good to know that reaching for a chemical fungicide is not mandatory. You can also fight this disease on the plant in an environmentally friendly way:
- Cut off the parts of the plant covered with a floury gray patina.
- Spray the plant repeatedly with a mix of 1 part of fresh milk and 9 parts of water.
- Alternatively, dust the infected flower with rock flour.
If possible, do not dispose of powdery mildew infected cuttings in the compost, as the fungal spores will spread again from there.
Within the diverse aphid family, one cunning species has specialized on the evening primrose plant.
If the tiny green or brown-black evening primrose aphids (Aphis oenotherae) colonize the flower, tackle the pest with the time-honored soap solution.
Mix 15 ml of pure soft soap or curd soap and 1 squirt of mineral spirits in 1 liter of water and spray the infested flower every 2-3 days.
Wintering the Evening Primrose
Whether as a biennial plant or perennial shrub; the evening primrose plant has adequate winter hardiness.
Since this varies depending on species and variety, we recommend the following precautions if you want to be on the safe side:
- Leave the foliage on the plant through the winter and cut it off only in the spring.
- Cover the bed with leaves, brushwood or reeds before the first frost.
- Place large containers on wood and wrap them with foil.
If the flower thrives in a small pot with a diameter of fewer than 12 inches (30 cm), move the plant into frost-free winter quarters.
Propagating Evening Primrose
You can leave evening primrose plants to propagate by seeding, or you can carry out targeted propagation using one of the following methods:
- Division of the root ball in spring or fall.
- Cutting non-flowering cuttings in early summer.
- Harvesting of seeds in autumn and sowing behind glass from March or direct sowing from June.
The ripe fruits of evening primroses cluster in flocks on the withered flower heads. If they take on a brown color and begin to open, the seeds inside are ripe.
Stored in a dark, dry screw-top jar, the seeds will retain their ability to germinate until spring and summer. Sow the seeds 1 inch (2-3 cm) deep in lean seed soil, in the open at a row spacing of 8 to 10 inches (20 to 25 cm).
Evening Primrose in a Pot
In a pot, evening primroses enrich evening leisure hours on the balcony with their beautiful blooms and aromatic fragrance.
Planted in a mix of normal potting soil and sand, protected from waterlogging by drainage of clay shards or grit, care is limited to watering during dry spells and monthly fertilizing from the second year.
The plant retains its neat appearance if you regularly clean out the faded flowers of the previous night. Before the first frost, prune the plant to the ground and put the pot in frost-free winter quarters.
My Evening Primrose Does Not Bloom
Don’t be surprised if an evening primrose plant fails to bloom in its first year. Since it is usually a biennial plant, it first invests its energy in growing a ground-hugging rosette of leaves.
If the supply of the flower is ensured in this way, in the second year the majestic flowering candle strives from this base towards the sky.
Are Evening Primroses Edible?
For generations, evening primroses had a regular place in the cottage garden, because their seeds and root are edible.
The well-known evening primrose oil is extracted from the seeds of the flower, which has made a name for itself in the field of medicine. It promises relief from stomach and intestinal disorders, skin irritations, and high cholesterol.
The root of the nostalgic plant is popularly known as ham root because it turns red when prepared. Harvested in the fall and cooked in water, the taste is reminiscent of salsify.
- Oenothera odorata ‘Sulphurea’: A delicate yellow flower that gives off a beguiling perfume scent at night. Its growth height is up to 24 inches (60 cm).
- Oenothera tetragona ‘Summer Solstice’: A large-flowered evening primrose plant whose deep yellow flowers spring from red buds. The growth height is 24-36 inches (60-80 cm).
- Oenothera speciosa ‘Siskiyou’: A magnificent ground cover evening primrose with pink flowers and enormous vigor. The growth height is 8-12 inches (20-30 cm).
- Oenothera speciosa ‘Alba’: A white flowering variety with prostrate shoots and long flowering period from June to September. The height of growth is 10 inches (30 cm).
- Oenothera rosea: Dense clusters of delicate pink flowers adorn the 10 inches (25 cm) tall evening primrose until October. This variety is ideal for containers.