How to Plant and Grow Loosestrife

Loosestrife (Lysimachia spp.) is a large plant family with more than 180 species of herbaceous and evergreen perennials. Types vary from stately plants suitable for borders to ones that serve as creeping groundcovers. Flowers vary, too; they can be shaped like cups, saucers, or stars and come in shades of white, yellow, pink, and purple. This vigorous grower suits a variety of settings, adding color through flowers and foliage and quickly filling empty spaces.

Although all varieties of loosestrife bear attractive flowers, these plants are also grown for their foliage. 'Alexander', for example, offers triple-tone leaves of medium green edged in softer green and rimmed in cream. Those leaves take on a pink tinge as they emerge in spring for an eye-catching show of color. Creeping Jenny (also known as moneywort) is a groundcover that adds bright splashes of gold foliage and flowers to partly shady areas.

Where to Plant Loosestrife

For the best results, plant loosestrife in a full sun location and rich, well-draining soil. In the heat of summer, the plant benefits from some partial shade. Tall varieties are perfect for the middle or back of a border if you bury them in containers to prevent rapid spread. The shortest varieties are best suited for groundcover.

Most types of loosestrife spread aggressively through underground rhizomes and have an ability to root anywhere a node touches the ground. Regular thinning keeps this plant under control. Surrounding loosestrife with a weed barrier or bamboo barrier restricts its running habit. Many gardeners cultivate this plant in a container to contain its rampant growth.

How and When to Plant Loosestrife

In spring or autumn, prepare a bed of nutrient-rich, well-draining soil, amending with compost or organic matter if needed. Dig a hole slightly larger than the loosestrife nursery container. Remove the plant from the container being careful not to damage any of the rhizomes or roots. Set it in the hole at the same depth it was in the container and backfill with the amended soil, pressing down with your hands to remove air pockets. Water the plant.

If you plan to install a bamboo barrier (also called a rhizome barrier), now is the time. Dig a circle around the plant well outside the current reach of the rhizomes and roots, and install a commercial barrier following the product instructions to restrict the spread of the plant.

Loosestrife Care Tips

Loosestrife is easy to care for when its basic needs are met.

Light

Plant loosestrife plants in full sun, which leads to the best foliage colors and prevents plants from flopping. For varieties with variegated or gold foliage, full sun may bleach out some of the leaves, especially in extreme southern exposures. If that's your worry, plant loosestrife where it will be sheltered from the sun in the afternoon. The plant will still perform beautifully.

Soil and Water

For best results, plant loosestrife in well-drained, consistently moist soil. Nutrient-rich soil fuels the perennial's rapid growth and extended bloom times. Water loosestrife weekly most of the year and twice weekly during the hottest parts of the summer. Note that some loosestrife species are former wetland plants that prefer wet soil. Read the nursery tag carefully for this information before you buy.

Temperature and Humidity

These perennials are hardy in USDA zones 4-9. They are hardy enough to survive a cold winter and return in spring. As long as the plants are watered regularly, they can grow in both high and low humidity. When the humidity is very high, cut back on watering.

Fertilizer

A single application in spring of a balanced fertilizer, such as a slow-release granular 10-10-10 product, is all this plant needs. Follow the product instructions for the correct amount to use.

Pruning

Loosestrife goes dormant during the winter. At that point, cut the plant back close to the ground.

Potting and Repotting Loosestrife

Gardeners may prefer to grow loosestrife in a pot outdoors to contain the plant. The container should have good drainage and be filled with the same well-draining amended soil used when loosestrife is planted in the ground. The container can be buried in the garden or a decorative addition to a patio. Either way, the plant will die back in the winter.

Because the plant dies back each year, it isn't an ideal houseplant, although it can be grown as a short-term addition to a home. In this case, plant it in a container filled with potting soil—the container must drain well—and position it where it receives the most sun possible.

Pests and Problems

In general, loosestrife plants are relatively unaffected by pests. Some are vulnerable to fungal infections that cannot be cured if kept in too-wet soil for an extended period.

How to Propagate Loosestrife

The easiest way to propagate loosestrife is through divisions, but they can also be propagated by stem cuttings or grown from seed.

Divisions: Use a sharp shovel to cut a circle several inches wider than the estimated width of the rhizomes and roots of an existing plant. Lift the plant out of the ground and separate the mass into several sections, preferably with your hands, using a sharp knife if necessary. Try not to damage the rhizomes. Each section should have a portion of foliage and undamaged rhizomes. Replant the sections immediately spaced at least 2 feet apart in a bed of prepared garden soil or put them in containers filled with well-draining potting soil.

Stem Cuttings: Prepare a pot by filling it with perlite or vermiculite. Cut a 4-inch section from a growing stem of the plant. Remove any foliage from the bottom half of the cutting and dip it in rooting hormone. Put it in the pot and firm the planting medium around it. Water lightly, cover the container with a clear plastic bag to retain humidity. Put it in a warm, bright area and check it occasionally to keep the medium and cutting moist.

In several weeks, begin to test for rooting by tugging gently on a top leaf, feeling for resistance. Resistance indicates the seedling has rooted. Remove the plastic bag and wait until the seedling develops roots at least an inch long before transplanting.

Seeds: The method for harvesting seed from all the many loosestrife species varies, but generally, wait for the seed head or pod to dry on the plant. Cut it from the plant and crush it to release the seeds. Store the seeds in a jar in a cool, dry place.

When ready, prepare a seed flat or pot with a sterile seed-starting medium. Sow the seeds on top of the medium and water them lightly. Cover the seeds and container with plastic or put them in a clear plastic bag. Put the bag in a warm, bright area until the seeds germinate, checking periodically to ensure the planting medium remains moist. Remove the plastic when you see growth. Give the seedlings time to develop a robust root system before transplanting them to the garden or a large container.

Types of Loosestrife

'Alexander' Loosestrife

Lysimachia punctata 'Alexander' is a stunning variegated selection with cream-edged leaves. This plant displays tall stalks of golden-yellow, star-shaped flowers that last almost the entire growing season. Zones 4-8

Whorled Loosestrife

Lysimachia punctata, or whorled loosestrife, has whorls of 1-inch yellow flowers along the upper part of leafy 3-foot stems. The dark 3-inch leaves, sometimes variegated with white, are also arranged in whorls. In the damp areas that this flower prefers, it may become invasive. Zones 4-8

Golden Creeping Jenny Loosestrife

Lysimachia nummularia 'Aurea' is a fast-growing groundcover for shade or partial shade. It bears round chartreuse foliage and grows 2 inches tall. It can spread indefinitely. Zones 4-8

Gooseneck Loosestrife

Lysimachia clethroides rises to 3 feet tall with stems topped with curved spikes of small white flowers. It is sometimes used as a cut flower. It is very aggressive and can become a nuisance. Zones 4-9

Purple Lance-Leafed Loosestrife

Lysimachia lanceolata var. purpurea emerges in spring with exciting deep-purple foliage that holds its color all season. Clusters of bright yellow 1-inch flowers nod atop 2- to 3-foot stems.

Loosestrife Companion Plants

Helenium

Long-blooming helenium lights up the late-season garden with showy daisy flowers in brilliant yellows, browns, and mahogany, centered with prominent yellow or brown discs. Many of the best cultivars are hybrids. All are excellent for cutting. Deadhead to extend bloom time and divide the clumps every couple of years to ensure vigor.

Calla

Funnel-shaped white callas represent a simple cool elegance in the garden, but the colored callas add a new dimension to the plant. Now available in a rainbow of hues, including lavender, purple, orange, yellow, and peach, these South African natives perk up container gardens and borders. The plants go dormant in colder winter areas of their hardiness range and do not emerge until temperatures warm up in late spring. Outside of their hardiness range, store the rhizomes in a frost-free place for winter.

Daylily

Daylilies are so easy to grow that you'll often find them growing in ditches and fields as escapees from gardens. Yet they look so delicate, producing glorious trumpet-shaped blooms in myriad colors. There are some 50,000 named hybrid cultivars in a range of flower sizes (the minis are very popular), forms, and plant heights. Some are fragrant. The flowers are borne on leafless stems. Although each bloom lasts only a day, superior cultivars carry numerous buds on each scape, so bloom time is long, especially if you deadhead daily. The strappy foliage may be evergreen or deciduous.

Veronica

Easy and undemanding, veronicas catch the eye in sunny gardens over many months. Some have mats with loose clusters of saucer-shaped flowers, while others group their star or tubular flowers into erect tight spikes. A few veronicas bring elusive blue to the garden, but more often, the flowers are purplish or violet blue, rosy pink, or white. Provide full sun and average well-drained soil. Regular deadheading extends bloom time.