Narrow-leaved Sundrops (Oenothera fruticosa)

Narrowleaf evening primrose (Oenothera fruticosa) is a flowering plant native to North America. The narrowleaf evening primrose grows in woodland areas and dry rocky soils and is sometimes cultivated as ornamental plants. The taxonomy of this species is controversial in the scientific community; they can interbreed freely with many other evening primroses.

I. Appearance and Characteristics 

Oenothera fruticosa, the narrowleaf evening primrose or narrow-leaved sundrops, is a species of flowering plant in the evening primrose family.

It is native to much of eastern North America, where it is found in a variety of open habitats, including dry woodlands, rock outcrops and moist savannas.

It is an erect herbaceous perennial growing to 20–90 cm (8–35 in) tall, with alternative, simple, entire or slightly toothed leaves. The saucer- or cup-shaped yellow flowers, 2.5–5 cm (1–2 in) in diameter, appear in late spring and summer. The fruit is a capsule that is strongly 4-angled or winged and shaped like a club.

Many varieties have been named, but the infraspecific taxonomy of this species is still in an unresolved state.

This species was originally described by Carl Linnaeus, who is identified in the name of the species as the authority “L.” . The taxonomy of this plant is complex and at times confusing as illustrated by the numerous synonyms, forms, and varieties.

Oenothera fruticosa grows best in sunny areas that have mostly acidic soil conditions and good drainage (sandy soils). The common sundrop is relatively resilient to drought, shade, extreme heat, and varying soil pH. Oenothera fruticosa is mostly found in grassy clearings, meadows, and along roadways in its native range .

The seeds of Oenothera fruticosa are approximately 1-3 mm long and are arranged in two rows within each locule. They also contain a persistent endotegmen that is one cell layer thick. In shape, the seeds are club-like and taper near the stem. The capsule of Oenothera fruticosa is approximately 1 inch in width and is visible May through November. The plants can be propagated by taking tip cuttings and is best conducted with adult plants at the beginning of its growing season (early spring) or late in its growing season (fall). Seeds must be planted in spring or fall and need to be germinated at approximately 70 degrees Fahrenheit.

The most common pollinators of Oenothera fruticosa are bees. Specific species of bees, such as Melissodes frimbriatus and Lasioglossum oenothera, seem to specialize on Oenothera fruticosa. In addition to these specialized pollinators, Oenothera fruticosa also attracts songbirds, hummingbirds, and an array of non-bee pollinators to its yellow petals. Oenothera fruticosa is susceptible to heterospecific pollen transfer from pollinators.  

II. How to Grow and Care

Fruticosa Oenothera is a pretty low-maintenance perennial plant. Here’s how you can properly take care of your yellow sundrops flower.

Sunlight

Narrowleaf evening primrose enjoys a lot of light (at least 8 hours a day) and should be cultivated under full sun, but it can also withstand partial shade. Well-ventilated, sunny areas in the courtyard are optimal for planting narrowleaf evening primrose. If it is too shaded, the plant will grow poorly and produce fewer flowers. If cultivated indoors, it is important to pick the sunniest spot for your plant.

Temperature

Narrowleaf evening primrose is very tolerant of cold and can withstand temperatures down to -20 ℃. Its optimal temperature for growth is 18 to 24 ℃. Temperatures above 27 ℃ are not favorable, as narrowleaf evening primrose is not well-adapted to withstand prolonged, intense heat.

Narrowleaf evening primrose prefers a dry-to-medium humid environment and is tolerant of drought. The soil should not be too dry during cultivation, especially if the aim is to encourage the plant to grow vigorously and produce numerous flowers. Narrowleaf evening primrose doesn’t tolerate waterlogging, so the well-draining substrate is very important.

Watering

Narrowleaf evening primrose is drought tolerant and can be used for xeriscaping (landscaping without irrigation). It does not tolerate waterlogging or excess moisture in the soil. If the plant is potted, it should be watered deeply once a week. Be careful not to water the plant too often if it’s planted in a pot; excess moisture in the soil encourages root rot.

If the plant is cultivated outdoors, it should be watered deeply after planting in the spring to promote growth, and only occasionally during the summer (when the days are too dry and hot). Natural precipitation provides enough water during the rest of the year.

Soil

Narrowleaf evening primrose can grow on a variety of different soil types, but it prefers light, loamy, sandy soil with medium moisture and good drainage. If you plant it in clay, improve the nutrient content and drainage of the soil by adding sand, leaf mold, some organic fertilizer, and crushed coal residue. The soil should be neutral, slightly acidic, or slightly basic (pH 5.5-7.5).

Fertilizing

Narrowleaf evening primrose isn’t that demanding when it comes to fertilization. It can grow even in poor soil. If you want to encourage your plant to grow and flower vigorously, mix organic fertilizer and humus with the substrate before planting. Topdressing is usually not required during the growing season. To promote flowering, apply liquid fertilizer with a high ratio of phosphorus and potassium every half a month.

Planting Instructions

Narrowleaf evening primrose is usually propagated with seeds. For annual species and warmer climates, sow in early spring or late summer. Biennials should be planted in the early days of fall. Soak the seeds in water for 5-10 hours and remove them once inflated. To prepare the substrate, spread a layer of coarse grain or rubble in the seedling container to ensure smooth drainage and mix with organic fertilizer.

Sow the soaked seeds in the substrate using tweezers, and make sure the seeds are evenly distributed. Cover the seeds with a thin layer of soil. Keep the seeding substrate moist at all times and temperatures between 18 to 21 ℃. The seeds should germinate within 10-15 days. Once they’ve developed 3-5 leaves, transplant.

Pruning

Narrowleaf evening primrose should be cut back to the ground after the leaves dry in late fall. This promotes vigorous growth and abundant new foliage in the spring. Cutting back can also be performed after the winter, during the first days of spring. Proper pruning reduces the probability of pests and diseases in the following year.

Propagation

You can propagate your flowers via their seeds. They are very easy to spread, so take care to keep them in check. Since these plants are native to dry woodlands and sunny savannas, transplant your store-bought or divided sundrops in a sunny area with a good amount of light and heat. They will drop their seed capsule after blooming and reseed easily wherever they are planted.

Pests and Diseases

This plant is fairly easy to grow since it is resistant to pests and diseases. However, here are some growing problems that your fruticosa oenothera might face.

Growing Problems

Make sure that your Oenothera fruticosa gets at least 6 hours of sun during the day since it needs direct sunlight to thrive, bloom and form in your garden. Also, don’t over-water or fertilize your plant, as it prefers dry soil.

Pests

It is resistant to pests. While a few opportunistic pests may nibble on it, it shouldn’t become a problem.

Diseases

It is not susceptible to any diseases other than a few leaf spots that do no serious harm. Your primrose won’t have any significant disease problems. This is why it’s a great plant to grow.

Overwintering

When grown within its recognized hardiness range, Narrowleaf evening primrose does not require any protection against winter cold. But you should withhold water and let the plants go somewhat dry during the late fall and winter, as they dislike sitting in damp soil during cool weather. You may want to cut back and destroy the old flower heads and stems to prevent volunteer seedlings from sprouting up in the spring.

III. Uses and Benefits 

• Ornamental uses

The Evening Primrose is mostly used as a groundcover, borders, in cottage gardens, rock gardens, and wild gardens.  

It works well with Oenothera Biennis L. and Oenothera Speciosa plants. 

Since it is drought tolerant, it makes a great addition in the xeriscape landscape and low-water garden.

The attractive seed pods left behind by the flowers add to the ornamental feel of the garden. 

This plant attracts various pollinators, including hummingbirds, native bees, and butterflies.

• Other uses

The Cherokee parboil the leaves, rinse them and cook in hot grease as a potherb. In the modern day, the narrow-leaved sundrop is primarily a garden specimen. Historically Oenothera fruticosa was used by Native American tribes for a multitude of aliments. The tribes that used this species included the Iroquois, Cherokee, and Ojibwa. Although the tribes differ, the reasons that they used the narrow-leaf evening primrose were similar. Its uses included helping with stomach issues, weight loss, bruising, and hemorrhoids. It is unknown at this time if Oenothera fruticosa is medically effective. Oenothera fruticosa has been included in research for breast cancer.

As a garden specimen the narrow-leaved sundrop is used in a variety of different ways. For landscaping, Oenothera fruticosa is used as a barrier or border plant. Not only is the narrow-leaved sundrop used in landscaping, but gardeners include this plant in pollinator gardens, rock gardens, cottage gardens, and native gardens for their ability to attract pollinators and their beautiful yellow petals. Oenothera fruticosa is a host plant of the pearly wood nymph, memphis moths, and primrose moths. The seeds of Oenothera fruticosa are consumed by birds including the eastern goldfinch and mourning dove.