Lycianthes
( lye - see - AHN - theez )
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At-A-Glance InformationCommonly called Blue Potato Bush, Paraguay Nightshade, Blue Potato Vine, Potato Tree or Royal Robe, this genus includes evergreen species of shrubs native to the tropical Americas and Asia. They can take the form of herbaceous subshrubs, scrambling climbers, or evergreen shrubs and small trees. Blossoms are typically star-shaped to trumpet-shaped, and can be white to shades of purple, often with bright golden-yellow centers. Foliage is typically bright green. The forms most commonly seen in gardens can reach 6 to 12 feet tall and a little less wide, and are grown as large shrubs or pruned into small trees. Use these plants as specimens or accents in mixed beds and borders, as an informal hedge or screen, espaliered against fences or walls, or trained into a patio tree. Take care when planting Lycianthes in the garden, as plant parts are highly toxic to humans and pets if ingested, including the flowers, leaves, and shiny berries. Direct skin contact with plants can also cause contact dermatitis in sensitive individuals.
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Lycianthes Species and Varietals
Lycianthes is a member of the plant family Solanaceae and includes 150 to 200 distinct species. Plants in this genus are closely related to Capsicum (Pepper) and Solanum (Potato and Tomato). These versatile plants grow best in USDA hardiness zones 8-11 or Sunst growing zones 12, 13, 15-24, H1 and H2. To find your zone, click here: Zone Map.
Lycianthes rantonetii (Solanum rantonetii) (Blue Potato Bush, Paraguay Nightshade, Royal Robe, Potato Tree)
This species reaches 8-12 feet tall and 6-10 feet wide at maturity. It can also be staked and grown into a tree or with support grown into a vine or espalier. Leaves are bright green and flowers are violet blue and flower throughout the year. This species is considered an invasive or naturalized garden escapee in coastal Australia. Cultivars are listed and described below:
This species reaches 8-12 feet tall and 6-10 feet wide at maturity. It can also be staked and grown into a tree or with support grown into a vine or espalier. Leaves are bright green and flowers are violet blue and flower throughout the year. This species is considered an invasive or naturalized garden escapee in coastal Australia. Cultivars are listed and described below:
'Lynn's Variegated'
With white to grey margins and deep blue-purple flowers. To 6-10 feet tall and a little less wide. |
'Royal Robe'
With deeper, rich violet purple flowers. To 6-8 feet tall and as wide. |
'White' ('Alba')
With white blooms with yellow centers. To 4-6 feet tall and 3-4 feet wide. |
Caring for LYCIANTHES
Take care when planting Lycianthes in the garden, as plant parts are highly toxic to humans and pets if ingested, including the flowers, leaves, and shiny berries. Direct skin contact with plants can also cause contact dermatitis in sensitive individuals. Plant Lycianthes in a space in the landscape that receives full sun to light shade; ideally, they appreciate between 6 and 8 hours of sun each day for the most profuse blooms. In particularly warm climates, provide them with some afternoon shade when temperatures are at their peak. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 6.0 and 7.8 (slightly 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, these plants are considered decently drought tolerant, able to get by on rainwater alone for most of the year. During the rest of the year, water deeply when the top 1 to 3 inches of soil feels dry to the touch.
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. Pruning is simple; remove any damaged, diseased, or dead foliage at any time during the growing season, and remove spent flower spikes to neaten up the appearance of plants and encourage reblooms. To prune young plants into tree-form, prune off any branches that emerge under the desired canopy height, being careful to not remove more than 30% of the plant's canopy at any one time. These plants can get a little bit leggy, especially if they are not grown in full sun. If this occurs, it is possible to create a bushier habit through routine pinching and pruning of longer branches. Prune the entire shrub yearly after flowering fades to maintain its shape and to remove dead or overgrown branches. These shrubs and trees can survive in the landscape for 15 to 20 years or more if properly cared for before needing to be replaced.
Caring for Lycianthes in Containers
Lycianthes shrubs and small trees can be grown in the ground, but can also do well in containers on patios or balconies. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. When they are mature, they will need a large container that is at least 16 to 20 inches wide and 14 to 18 inches deep. Heavy pots are recommended, as these trees can topple over in the wind, especially when pruned up into trees. 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.
Lycianthes 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. To prune young plants into tree-form, prune off any branches that emerge under the desired canopy height, being careful to not remove more than 30% of the plant's canopy at any one time. 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.
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. Pruning is simple; remove any damaged, diseased, or dead foliage at any time during the growing season, and remove spent flower spikes to neaten up the appearance of plants and encourage reblooms. To prune young plants into tree-form, prune off any branches that emerge under the desired canopy height, being careful to not remove more than 30% of the plant's canopy at any one time. These plants can get a little bit leggy, especially if they are not grown in full sun. If this occurs, it is possible to create a bushier habit through routine pinching and pruning of longer branches. Prune the entire shrub yearly after flowering fades to maintain its shape and to remove dead or overgrown branches. These shrubs and trees can survive in the landscape for 15 to 20 years or more if properly cared for before needing to be replaced.
Caring for Lycianthes in Containers
Lycianthes shrubs and small trees can be grown in the ground, but can also do well in containers on patios or balconies. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. When they are mature, they will need a large container that is at least 16 to 20 inches wide and 14 to 18 inches deep. Heavy pots are recommended, as these trees can topple over in the wind, especially when pruned up into trees. 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.
Lycianthes 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. To prune young plants into tree-form, prune off any branches that emerge under the desired canopy height, being careful to not remove more than 30% of the plant's canopy at any one time. 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.
Propagation
Blue Potato Bush is most easily propagated by cuttings. For information on how to complete this process, follow the instructions below:
Propagating Lycianthes by Cutting
Propagating Lycianthes by Cutting
- Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
- In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
- Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
- Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.
Problems and Pests
Certain Lycianthes species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Blue Potato Bush can be affected by the following pests and diseases in the garden:
- Aphids
- Whiteflies
- Spider Mites
Gallery
Blue Potato Bush can be grown either in-ground or in pots.
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These shrubs are known for their profuse purple flowers that appear throughout the year.
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The flowers of related Solanum shrubs (pictured) are very similar to those on the Blue Potato Bush.
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Videos
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How to grow and care for these beautiful shrubs.
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Propagating Blue Potato Bush.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 424, Lycianthes rantonnetii
