Juncus

juncus

( JUN - kus )

At-A-Glance Information

This genus includes perennial species of grass-like plants commonly called Rush. These plants need full sun to light shade and ample water to perform well in the garden. They have cylindrical stems and inconspicuous flowers near stem tips. Plant Juncus alongside grasses or aquatic plants at the edges of pools or other bodies of water, grow them in containers, or use them as interesting accents in mixed beds and borders. Their deep roots make them great candidates for erosion control in wet, boggy, or sloped areas of the landscape. Take care when planting Juncus in the landscape, as some species can cause severe, sometimes fatal reactions in humans, pets, and livestock if ingested.

Juncus Species and Varietals

The genus Juncus is the type genus member of the plant family Juncaceae, and includes 340 species. The best growing zones for Juncus are USDA hardiness zones 4-11, though this varies somewhat depending on the species cultivated. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Juncus decipiens (Lamp Rush, Soft Rush, Common Rush, Corkscrew Rush, Curly-Wurly Rush)
This species of Rush grows well in USDA hardiness zones 5-9 or Sunset growing zones 1-24 and H1 and is native to eastern Asia. A commonly grown cultivar, 'Curly Wurly' (pictured; also called 'Spiralis') has corkscrew stems. This species can be invasive in Ireland, Europe, and the United States.

Juncus effusus (Soft Rush, Common Rush, Bog Rush, Mat Rush, Lamp Rush, Pacific Rush)
Best in USDA hardiness zones 2-9 or Sunset growing zones 1-24 and H1; this species reaches 2.5 feet tall and just as wide. Green stems reach up to a quarter inch thick. Varieties include 'Carman's Japanese' (to 2 feet tall), Juncus effusus spiralis 'Twister' and 'Unicorn' (with corkscrew foliage), and 'Quartz Creek' (to 3 feet tall). This species is considered invasive in Hawai'i, New Zealand, Australia, and wet environments throughout North America.

Juncus inflexus (Blue Medusa Rush, Hard Rush, Blue Rush, European Meadow Rush, Blue Arrow Rush, Incurved Rush)
This species reaches 18 inches tall and 2 feet wide, and grows well in USDA hardiness zones 4-9 or Sunset growing zones 3-9 and 14-24. It has blue, thick stems and is more drought tolerant than other species tend to be. Variety 'Blue Arrows' reaches 3 feet tall at maturity. This species is considered invasive in North America, Oceania, South America, and various islands including Sri Lanka and Java.

Juncus patens (California Gray Rush, Spreading Rush, Common Rush, Grey Rush)
Best in USDA hardiness zones 4-9 and Sunset growing zones 4-9 and 14-24, this species is native to California and Oregon, and reaches 2 feet tall and just as wide. Stems are upright, stiff and green to grey-green. California Gray Rush can tolerate more heat and drought even than Juncus effusus, but does thrive in moist soil or shallow water. Variety 'Carman's Gray' is a variety with great gray color.

Caring for Juncus

Take care when planting Juncus in the landscape, as some species can cause severe, sometimes fatal reactions in humans, pets, and livestock if ingested. Choose a spot in the landscape that has formal irrigation or is close to a water source. They do well in full sun to partial shade; ideally, they should be getting between 6 and 8 hours of sun each day for best growth, but do appreciate some late afternoon shade, especially in warmer climates. Space Juncus between 12 and 24 inches apart for best coverage and airflow. These plants will spread over time to form colonies via underground rhizome roots, eventually filling in any gaps in planting space. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 6.2 and 7.0 (acidic to neutral). 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, they appreciate consistent, regular waterings and even grow well in boggy or water-adjacent microclimates.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. Prune off dead, damaged, diseased, or scorched leaves as necessary to improve the appearance of the plant. Every few years, check the growing area where Juncus grasses are planted, and determine whether they need to be divided. Acorus plants can live for between 5 and 10 years in the landscape before needing to be replaced.

Caring for Juncus in Containers
Planting these grasses in containers is a great option for gardeners concerned about their spreading capabilities and somewhat invasive nature in certain regions. Choose a container that is at least 1 to 2 gallons (8-10 inches in diameter). Ensure that the pot has adequate drainage holes on the bottom to allow for excess water to flow away. Fill with a well-draining potting mix amended with organic material and perlite, and top with a layer of mulch to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water regularly as the plant establishes itself in its new home. Once established, waterings can be lessened. Juncus plants grown in containers will need more frequent irrigation than those grown in the ground. As a general rule of thumb, water whenever the top few inches of soil feels dry to the touch. Prune to remove dead, damaged, or diseased foliage at any time during the growing season. Every few years, check the bottom of the pot to ensure that the plant is not outgrowing its root space. If roots are growing through the drainage holes in the bottom of the container, it is a good indication that it needs to be potted up; choose a slightly larger container and repot. Juncus can also be divided every once in a while to prevent them from outgrowing their container. For instructions on how to successfully divide Juncus plants, see the propagation section below.

Propagation

These plants spread via underground rhizome roots, and the best way to propagate them is by dividing. This process is necessary even if the goal is not to propagate the plants, especially if growing in a cramped space or container. This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil, compost, and pots (only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in spring or fall (after the plant has entered dormancy and been cut to the ground, but before it has begun its new spring growth). To propagate by division, follow these steps:

Gather your materials. Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the rhizome roots. Once you have worked it up out of the ground, lay it out.
Start to tease apart the roots with your fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick section.
Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divided rhizomes about an inch under the soil surface and water thoroughly.
Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Water regularly as it establishes a strong root system.

Problems and Pests

Certain Juncus species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Juncus grasses can be susceptible to developing issues with the following pests and diseases in the landscape: