Read a commented bitterroot profile here with information on growth, winter hardiness and use. The best tips for sowing, planting and Lewisia care.
What is bitterroot and how to care for this plant?
Bitterwort (Lewisia cotyledon) is an easy-care, hardy perennial that is ideal for rock gardens and dry stone walls. It has fleshy leaves and produces numerous colorful flowers. When planting, pay attention to permeable, lime-poor soil and protect the plant from waterlogging.
Profile
- Scientific name: Lewisia cotyledon
- Family: Springwort family (Montiaceae)
- Synonym: porcelain florets
- Origin: California
- Growth type: evergreen perennial
- Growth height: 5 cm to 25 cm
- Growth width: 15 cm to 25 cm
- Leaf: oval-ovate, spatulate, lanceolate
- Flower: panicle-shaped raceme
- Root: fleshy taproot
- Winter hardiness: hardy
- Use: rock garden, open ground, pot, flower box
Growth
Lewisia cotyledon is the best-known species of the bitterroot genus from the spring herb family (Montiaceae). In its Californian home region, the perennial colonizes barren rock faces and stony areas with daring calmness. In this country, the porcelain rose is valued as a graceful rock garden plant. These key growth data explain why the Lewisia flower is tough:
- Growth type: succulent, evergreen perennial with a basal rosette of leaves from which colorful inflorescences rise on long stems.
- Growth height: 5 cm to 25 cm (during flowering).
- Growth width: 15 cm to 25 cm, older perennials up to 30 cm (including daughter rosettes).
- Roots: long, fleshy taproot leads into a tuberous caudex as a starting point for the rosette of leaves.
- Gardenically interesting properties: hardy, undemanding, non-toxic, easy to care for.
Video: Porcelain roses in full bloom
Leaf
Decoratively, the evergreen leaves gather to form flat, spread-out rosettes with a diameter of up to 30 centimeters. You can recognize a bitterroot leaf by these characteristics:
- Leaf shape: variable from oval-ovoid to spatulate to elongated-lanceolate, stalked or sessile.
- Leaf size: 4 cm to 12 cm.
- Leaf color: light green to dark green.
- Leaf edge: curled, toothed or smooth.
- Texture: fleshy, waxy covered.
Bloom
Bitterwort flowers are enthroned above the leaf rosettes on stems up to 30 centimeters high and arranged in a circle. In gardening terms, the perennials are called porcelain florets. These characteristic features make Lewisia cotyledon unmistakable:
- Inflorescences: panicle-shaped racemes with 10 to 50 individual flowers.
- Single flower: radiating with 7 to 10 delicate petals, 2 cm to 4 cm in diameter.
- Flower colors: pink-purple, bright pink or salmon, white, yellow or two-tone, cream or dark striped.
- Flowering time: April/May to July/August.
The flower stems are mostly leafless. Below the inflorescences there are small, pointed bracts measuring 2 mm to 4 mm. The 5 to 10 stamens are free. Pollinated star flowers turn into tiny capsule fruits containing 4 to 15 black seeds.
Winter hardiness
Lewisia cotyledon is naturally hardy down to -20° Celsius. However, a wet and cold Central European winter puts the certified frost hardiness to the test. For this reason, the care program for porcelain roses includes a recommendation for light winter protection.
Usage
Bitterwurz's steep career began as a cheerful splash of color in the rock garden. Since our summers have been characterized by new heat records and desert-like drought, creative hobby gardeners have discovered these possible uses for porcelain roses:
| Garden | Idea | Balcony/Terrace | Idea |
|---|---|---|---|
| Rock garden plant | Color accents in the gravel bed | potted plant | Mini rock garden in the terracotta bowl |
| Drywall | beautiful in cracks in the wall | Flower box | next to cat paws, blue pillows etc. |
| Alpinum | Dream Team Bitterroot and Blue Gentian | Bucket | Underplanting buddleia, climbing trumpet |
| Herbal spiral | in sunny stone joints | Flower staircase | in the pot on the sunniest level |
Planting bitterroot
In the hobby garden, sowing and planting bitterroot go hand in hand. Ready-to-plant porcelain florets can be purchased almost all year round in tree nurseries and garden centers for around 5 euros. In the right location, the distinctive natural beauties germinate, thrive and bloom magnificently. The best planting tips for Lewisia to read:
Location, soil, substrate
In order for porcelain roses to germinate cheerfully and bloom lushly all summer long, these site conditions are important:
- Sunny to shady location (partial shade reduces the abundance of flowers).
- Warm, rain-protected location, ideally under an eaves.
- Stony, humus-rich, lime-poor soil, well-drained, without the threat of waterlogging when it rains.
The best protection against root rot in pots, containers and flower boxes is a coarse-grain, low-lime substrate (€16.00 at Amazon). A mixture of peat-free potting soil, coconut fiber as a peat substitute and lava granules in equal parts has proven to work well in practice.
Preparing for sowing – tips & tricks
Bitterroot seeds are cold germinators. A cold stimulus is required for germination. Simple pre-treatment methods overcome the natural germination inhibition. These options are available:
- Best option: direct sowing in late summer or autumn for a natural cold stimulus.
- Refrigerator method: Place seeds and moist potting soil in a sealed plastic bag in the vegetable compartment for 6 weeks.
- Balcony method: place a seed tray covered with fleece in a protected location (snow cover is advantageous).
- Extra tip: Soaking seeds in diluted gibberellic acid (the plant's own growth hormone) for 12 hours stimulates germination without any prior cold stimulus.
Sowing indoors and outdoors
Porcelain florets grown on the windowsill start the gardening season with a vital growth lead. After the recommended pretreatment, sow the now germinating seeds in small pots made of coconut soil. Because the cold germinators are also light germinators, press the seeds a little. Spring pots are later placed in the ground with the young plants. Keep the seeds slightly moist on the bright, warm windowsill. Following germination, a cooler location of around 18° Celsius is advantageous.
The time window for direct sowing is open from September to March. Prepare a coarse, weed-free seedbed for bitterroot seeds. Sow the seeds 5mm to 10mm deep. The seeds are watered with a fine spray of lime-free water. In spring the strongest porcelain florets are isolated at a distance of 20 cm to 25 cm.
Planting
Bitterroot perennials grown on the windowsill or purchased ready to plant are easy to plant. Tried-and-tested tips for beds and balconies:
- The planting hole is twice as large as the spring pot or the root ball.
- As a starter fertilizer, mix a handful of horn shavings into the excavated soil in the bed.
- Pour the substrate into a pot, bucket or flower box over drainage made of expanded clay or coarse sand.
- A 3-5 mm high separating layer of lava granules or sand around the root collar prevents root rot.
Plant bitterroot rosettes at a slight angle so that rainwater can drain away better. The planting distance in the bed is 20 cm to 25 cm. Place porcelain florets in the soil in the balcony box at a distance of 15 cm.
Excursus
Homage to a legendary explorer
For good reason, the Lewisia genus is dedicated to the American pioneer Meriwether Lewis (1774 in Ivy, Colony of Virginia; 1809 in Tennessee). As private secretary to American President Thomas Jefferson, Lewis played a key role in the legendary Lewis and Clark Expedition. From 1804 to 1806 he documented the risky expedition from Saint Louis to the Pacific. Among other things, Meriwether Lewis gained valuable insights into previously unknown plants and animals.
Care for bitterroot
Bitterwurz is one of the easiest-care perennials for rock gardens, dry stone walls and balconies. Protection against waterlogging plays a key role. Propagation is simple and uncomplicated. All important tips for perfect Lewisia care in a nutshell:
- Watering: water sparingly when the soil is noticeably dry using collected rainwater.
- Fertilizing the bed: fertilize with compost or horn shavings in March/April.
- Fertilizing in planters: Add liquid fertilizer to the irrigation water every 4 weeks from April to July.
- Cutting: cut off withered flower stems just above the rosette of leaves.
- Repotting: Repot bitterroot in spring when daughter rosettes touch the edge of the container or the first roots grow out of the opening in the ground.
Wintering
In the bed, winter protection aims to keep constant rain, meltwater or blazing winter sun away from the evergreen leaves and succulent roots. On the balcony, the root balls are vulnerable to frost in the limited substrate volume. This is how you overwinter bitterroot properly:
- In the open field, cover the perennials with coniferous twigs or breathable garden fleece.
- Cover plant containers with bubble wrap or jute, place on wood in a rain-protected niche.
- Potted plants should ideally be frost-free overwintered under glass, either light or dark.
- Winter care: water sparingly (during clear frost on mild days), do not fertilize.
Propagation
For vegetative propagation, you can cut off daughter rosettes, dig them up with roots and plant them in the new location. Leaf cuttings root quickly in a pot with coconut soil or growing substrate.
Popular varieties
These varieties combine the undemanding frugality of the original Lewisia species with colorful flowers:
- Rainbow: Lewisia premium variety with semi-double flowers in the colors of the rainbow.
- Sunset Strain: the rock garden is colorful with pink, red, orange and yellow flowers.
- Lewisia 'Eldora': interesting garden perennial with pink cupped flowers, 30 cm high and just as wide.
- Lewisia 'Mountain Dreams': fantastically beautiful Lewisia flower with yellow flowers from May to July, 15-30 cm tall.
- Lewisia longipetala: little sister of Lewisia cotyledon, cushion-forming, pink flowers, lanceolate leaves, 10-15 cm small.
FAQ
Is bitterroot poisonous?
Bitterwurz contains neither toxic nor medicinal ingredients. This characteristic makes all Lewisia species ideal perennials for the family garden with pets.
How is the pretreatment of cold germination seeds with gibberellic acid?
In a weak solution of gibberellic acid and water, cold germs overcome their natural germination inhibition. Because the acid itself is not water-soluble, proceed as follows: Mix 0.1 g gibberellic acid with 5 ml pure alcohol (pharmacy). Once the crystals have completely dissolved while stirring constantly, add 95 ml of room temperature water. Now hang the seeds in the solution in a tea strainer for 12 hours. This way the liquid stays clean and can be frozen for further uses.
Are porcelain florets hardy?
In the stony, permeable, sun-drenched and rain-protected location, porcelain florets are hardy down to -20° Celsius. Wet and cold weather, cold frost and pot cultivation, of course, put the frost hardiness to a tough test. For this reason, we recommend light winter protection for bitterroot. A cover made of leaves and spruce branches protects the succulent roots from waterlogging. Plant containers are covered with fleece and overwintered on a wooden base in front of the protective house wall. In harsh winter regions, it is advisable to spend the winter in frost-free winter quarters.
