Eriogonum Umbellatum [er-ih-OG-uh-num, um-bell-AY-tum] is a highly variable perennial flowering plant species of the family Polygonaceae, along with the silver lace vine.
It is commonly known as the knotweed family and native to western North America, from California to Colorado to central Canada.
The plant is generally known by the common name sulphurflower buckwheat, or simply sulphur flower, due to its flower color.
It is also sometimes referred to as sulphurflower wild buckwheat, with reference to its genus Eriogonum, commonly known as wild buckwheat.
The scientific name of the plant, on the other hand, refers to the shape of its flowers – umbellatum means ‘umbel-like’.
Eriogonum Umbellatum Care
Size & Growth
Sulphur flower is considered a highly variable plant because it has numerous varieties, which are often highly distinct from each other and hard to identify.
The plant also grows in a variety of habitats in its native range but is most commonly seen growing in dry, rocky mountain slopes and ridges, rocky forests and foothills.
Due to the diverse growing conditions and many varieties, sulphurflower buckwheat can either grow as a perennial herb or a sprawling shrub.
Consequently, the height of the plant also varies significantly – it can grow from anywhere between 3” inches to 3’ feet.
However, regardless of their habitat or height, all sulphur flower plants have a tendency to spread in width and form loose mats of leaves, growing near the base of the stalks.
The leaves are green from above, but often have a grayish tinge on the lower surfaces and are somewhat spatula-shaped.
They also have a woolly texture, which gives the plants a unique appearance.
This wild buckwheat species also has a long life expectancy – once successfully established, the plants can live for over 20 years.
Flowering and Fragrance
While most varieties of this wild buckwheat species produce bright yellow flowers (hence, the name sulphur or sulfur flower), some also produce white or purple flowers.
Whatever the color is, the flowers are conspicuous, fragrant, slightly tubular, and are produced at the ends of long, erect stalks in umbels; rounded flower clusters.
The flowering stalks are about 12” inch tall and leafless.
The flower clusters, on the other hand, are about 4” inch wide and are subtended by whorls of leaf-like bracts.
In most varieties, the flower color gradually changes to orange or red.
The blooming period starts in June and lasts till September (from early summer to late summer or early fall).
Light & Temperature
Sulphur flower buckwheat can grow in full sun to partial shade.
It is also quite tolerant of cold and can survive in temperatures as low as 0° degrees Fahrenheit (-18° C).
Since the plant naturally grows in dry habitats, it doesn’t like humid weather.
The plant is hardy to USDA hardiness zones 4 to 8.
Watering and Feeding
In its native range, the plant generally grows on dry mountainous slopes and ridges hence, its water requirements are very low.
Watering three to four times a month, at maximum, is enough for established sulphur flower plants.
Soil & Transplanting
This wild buckwheat species grows best in gravelly, circumneutral (having a pH between 6.8 and 7.2), and well-drained soils.
Sandy soil is also a good choice for growing sluphur flowers.
While the plant has a good tolerance for poor soils and drought, it cannot tolerate wet soils in winters.
If left in the wet soil during the winter season, the plant is most likely to die.
Grooming and Maintenance
Sulphurflower buckwheat is a low-maintenance plant and needs almost no care, once established.
How to Propagate Sulfur Flower Buckwheat
E. umbellatum is almost always propagated by seeds because the mature plants are nearly impossible to divide, or even transplant, due to their long taproots.
However, growing sulphur buckwheat plants from seeds is challenging as the germination is low.
For increasing the chances of germination, it is recommended to stratify the seeds for three months and add a thin layer of gravel or sand to the potting mix once the seedlings start to emerge.
This will help reduce damping-off, which is the major cause of seedling deaths.
The seeds are both commercially available and are manually collected from the three-sided achenes.
For those who do not know, achene is the term used for dry, single-seeded, indehiscent (remain unopened at maturity) fruit.
Sulfur Flower Buckwheat Pest or Diseases
The flowers of the plant are highly attractive to butterflies and serve as the larval host of many butterflies from the family Lycaenidae.
The flowers also attract bees whereas seeds of the plant attract different types of birds.
All in all, the wildflower attracts a wide range of pollinators.
Eriogonum Umbellatum Uses
Since sulphurflower buckwheat plants have mat-forming growing habit, they are most widely used for ground covers.
Since they have low water requirements and attract butterflies, sulfur buckwheat plants are also highly popular for growing in rock gardens and butterfly gardens.
According to research, some Native American communities used certain parts of this plant for medicinal purposes.
However, no such use is reported in modern times.