How to Grow and Care for Evening Primrose

Evening primrose (Oenothera biennis) has plenty of admirers thanks to its beautiful and delicate appearance, but just as many people view this feisty floral as an invasive and temperamental weed. Native to North America, the flower is best sown in late fall, will grow quickly, and bloom each summer, beginning its second year of life. Fragrant, four-petaled flowers bloom above a basal rosette of leafy, branched stems.

Evening primrose self-seeds, so it's possible that, unless properly cared for, it could easily take over your garden. Still, it has pretty, lemon-scented yellow flowers that lure many gardeners with their beauty. The plant's blooms open in the late afternoon and evening and close throughout the day, attracting a different set of nighttime pollinators, such as moths and bats.

Evening Primrose Care

Here are the main care requirements for growing evening primrose:

• Plant in well-draining soil with full sun exposure.
• Prefers loamy or sandy soil.
• Water regularly, but keep an eye out for root rot from overwatering.
• Does not require pruning, but snipping spent blossoms is welcome.
  

Light

Contrary to what you may believe about a plant that only blooms at night (making it perfect for moon gardens), evening primrose loves sunlight. It should be grown in a spot that gets full sunlight (or partial shade) and somewhere that the plant can soak in at least six to eight hours of warm sunlight daily.

Soil

Another major requirement for growing evening primrose successfully is soil that boasts good drainage. That being said, the soil should still retain moisture, just not become water-logged. Consider adding a thick layer of mulch atop the soil to help keep the roots cool throughout the summer. Evening primrose can grow well even in rocky, sandy soil.

Water

Evening primrose does best with adequate regular watering and will need a bit more water if grown in an especially hot climate during the summer. However, if you notice any discoloration or browning on the plant's many leaves, that's a sure sign that your evening primrose is getting too much water and is likely suffering from root rot or a fungal disease.

Temperature and Humidity

While it blooms and grows best during late summer, evening primrose prefers to be cool rather than warm. The plant needs to get established with roots and foliage during the cooler early months of spring to flower well come summer. Too much heat early in its life can cause the plant to become leggy or resemble a weed in appearance.

Fertilizer

Fertilizer is not a necessary addition to your evening primrose care regimen—it will grow just fine without the additional nutrients. However, if you are working with particularly bad soil, you can amend your mixture with some organic material.

Types of Evening Primrose

• 'Greencourt Lemon' (Oenothera macrocarpa): features pale green-yellow flowers atop red stems
• 'Lemon Drop' (Oenothera): a lemon yellow, four-petaled flower that is a long-blooming and low-maintenance perennial
• 'Mexican Evening Primrose' (Oenothera speciosa):also known as "pinkladies," this type of evening primrose is known for its beautiful pink bell-shaped flowers
• 'Beach Evening Primrose' (Oenothera drummondii): usually found near sandy beaches in the California region; also called beach suncup due to its sunny yellow cup-like blossom

Pruning

Though evening primrose doesn't require deadheading, controlling the plant is much easier if you snip or pinch off the expired blossoms to prevent the plant from self-seeding. Be sure to discard the spent flowers instead of letting them fall to the ground.

Propagating Evening Primrose

The easiest way to propagate evening primrose is by seed.

How to Grow Evening Primrose From Seed

Evening primrose is typically grown from seed, and although you can buy the seeds online, you can just as easily collect seeds from large colonies of wild plants growing along the roadside.

1. Directly sow evening primrose seeds in autumn in a location that boasts full sun, where the soil has been previously cultivated.
2. Sow the seeds on top of the soil and water well.
3. After germination, thin the seedlings so that they are approximately 1 foot apart.
4. Allow the seeds to go through stratification to germinate. (If you sow seeds indoors, use a small container filled with moistened seed-starting mix, sow the seeds on top of the soil, cover, and place in the refrigerator to mimic a natural chilling period. Take out in late winter to pot up the plants when they have two sets of true leaves.

In its first year of life, evening primrose will not flower but will simply produce a leafy rosette at ground level. During the second year, a tall, stiff flower stem shoots up out of this base. About midway up this flower stem, secondary branching occurs, and the leaves become progressively smaller the farther you go up the flower stem. The four-petaled blooms that begin emerging at the start of summer are about 1 inch wide. They'll eventually die off and produce seeds, which are then spread throughout the landscape by various weather conditions or eaten by wild birds.

Potting and Repotting Evening Primrose

Some varieties of evening primroses can be grown in containers, but those with long root systems should not be potted. If you choose to pot evening primrose, select a deep container.

Overwintering

Evening primrose is a hardy perennial and can survive colder, winter weather.

Common Pests & Plant Diseases

Varieties of beetles eat the leaves of evening primrose, but they won't do enough damage to kill the plant. Otherwise, you can expect to see various other traditional garden pests periodically, including leafhoppers, lygus bugs, and aphids.

If you notice signs of infection on your plants, treat them with insecticidal soap or a diluted oil such as neem oil. Root rot is also a possibility if evening primrose is overwatered, so be sure the soil is well-draining.

Common Problems with Evening Primrose

Though evening primrose is a rather easy plant to grow and manage, it will sometimes show a few problems.

Decaying or Wilting

This is often the result of bacterial soft rot, which occurs at temperatures between 70 and 80 degrees Fahrenheit and affects plants that are sitting in soggy soil or very humid conditions.

Yellowing Foliage and/or Stunted Flowers

Fungal diseases are known to limit the plant's ability to take up water and nutrients, leading to yellowing of the leaves, stunted flowers, and root rot. Pull these flowers up and discard them to prevent the fungus from moving to other plants.

Discoloration of Foliage and Flowers

This can be caused by gray mold, which can cover the plant with fuzzy gray and brown spots. This happens even as the plant slowly succumbs to the resulting lack of nutrients. Pull the plants to prevent the spread.

From: thespruce