Rhamphospermum

( ram - fo - SPUR - mum )

At-A-Glance Information

This genus of flowering plants is closely related to Broccoli and Mustard, and produces annual plants with green foliage and yellow flowers. The most popularly cultivated species in this genus is Rhamphospermum nigrum, or Black Mustard, which is grown for its edible stems, leaves, flowers, and seeds, which are ground into a spice. Add these plants to your herb or vegetable garden or grow them simply to draw in pollinators.

Rhamphospermum Species and Varietals

The genus Rhamphospermum is a member of the plant family Brassicaceae, and includes just four species. They can grow in any zone, but thrive in USDA growing zones 6-9. To find your zone, click here: Zone Map.

Rhamphospermum arvense (Charlock Mustard, Field Mustard, Wild Mustard, Charlock)
These annual plants are native to North Africa, Asia, and Europe, and have naturalized in many other areas around the globe. Plants reach between 8 and 31 inches tall when mature, and produce green foliage and yellow flowers. Leaves are edible when young, and are typically boiled. Seeds can be ground into a mustard-like condiment. 70-75 DTM.

Rhamphospermum nigrum (Brassica nigra, Sinapis nigra) (Black Mustard)
These plants are annuals, native to cooler regions in North Africa, temperate Europe, and some areas in the Asian continent. It is widely cultivated for its dark brown to black seeds, which are typically used as a spice. Individual plants reach up to 4 feet tall and 28 inches wide. Yellow flowers bloom in summertime, which fade to reveal beaked seed pods that contain round seeds. Seed coats are removed and ground as spice, and young leaves, buds, and flowers are also edible. 80-95 DTM.

Rhamphopermum pubescens (Sinapis pubescens)
These perennial plants are native to the central Mediterranean (France, Italy, Sardinia, Sicily, Albania, Algeria, Tunisia, and Libya). They are relatively small, low-growing plants and are not typically cultivated as crops. This species is commonly considered to be weedy and undesirable in the garden.

Caring for Rhamphospermum

Rhamphospermum, or Mustard, plants are typically grown from seed each year. They will freely re-seed in the garden, providing edible greens for many years. Choose a space in the landscape that receives between 6 and 8 hours of direct sunlight each day. They can tolerate some shade, especially in the late afternoon when temperatures are at their peak. They grow best at temperatures that stay under 75 degrees Fahrenheit. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 5.0 and 8.0 (acidic to alkaline). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention.

Water new plantings regularly as they establish a strong root system in their new home. At maturity, keep soil consistently moist but not soggy. They do not need to be fertilized, though if soils are particularly poor, make sure to amend before sowing seeds. Prune regularly to encourage a bushier growth and remove yellowing or damaged leaves at any time during the active growing season in spring and early summertime. Pinching back the growing tips as young seedlings mature is recommended to encourage a bushier habit and produce more greenery for harvesting. Remove flowering stems as they form to extend the harvesting season for as long as possible. If you will be collecting seeds for propagation or culinary applications, make sure to leave a few flower stems on plants to mature. At the end of the growing season, pull plants and compost them.

Harvesting Rhamphospermum
Rhamphospermum, also called Black Mustard or Charlock, are cut-and-come-again plants that are harvested for their foliage. The seeds, flowers, and buds are also edible. For the mildest, most tender and palatable leaves, plants should be harvested before they produce flowers. To harvest leaves, use clean, sharpened scissors or snips to remove the larger, older outer leaves at their base, taking care to not nick any inner leaves in the process. This allows for multiple harvests from one plant. Alternatively, the entire plant can be harvested at one time by cutting it off at its base. Make sure to harvest these plants before hot weather sets in, as this will encourage the plant to bolt and form flowers, taking energy and nutrients away from the foliage. Leaves tend to become bitter once summertime heat comes in. Leaves have a sharp, peppery, pungent flavor (similar to those of Wasabi or Arugula plants), and are used raw or cooked.

Flowers and flower buds are also harvested, and have a peppery flavor. Harvest young, unopened buds before flowers open. The heads can be cooked and prepared like Broccoli. Once opened, flowers are commonly used raw as a garnish or to add a pop of mild spiciness to dishes. Seeds are used to make the condiment Mustard, and are strong and spicy. Once flowers have been pollinated, seed pods will form at the end of flower stems. Harvest these pods as they begin to turn from green to light brownish color. Make sure to harvest at just the right time, or the brittle pods will shatter and disperse the seeds. Harvest the entire flower stalk, and hang or lay them out to dry. Remove the seeds from the pods, and then separate them from the chaff. Seeds can be stored in an airtight glass or metal container away from heat, light, and moisture. Ground seeds lose their flavor more quickly than whole; they are best used freshly ground.