Paraguay nightshade (also known as blue potato bush) is a fast-growing shrub with slim arching stems and fragrant blossoms. It was once classified as Solanum rantonnetii, but is now more commonly referred to as Lycianthes rantonnetii. Some believe the plant is botanically related to potatoes and other nightshades (hence the common names), but Paraguay nightshade is grown for its ornamental appeal. So, count on this easy-to-grow plant to produce an abundance of brilliant violet and yellow flowers from summer well into fall.
As a garden accent, Paraguay nightshade has a lot going for it. Deer don't usually bother it, nor is it plagued by any significant pests or diseases. Plus, it’s pretty and prolific with blooms. In fact, in 2012, the Royal Horticultural Society gave Lycianthes rantonnetii their prestigious Award of Garden Merit.
That said, it’s worth noting that while the plant’s classification is still up for debate, it is a part of the nightshade family. As an ornamental shrub, it bears more in common with Atropa belladonna (deadly nightshade) and bittersweet nightshade than with eggplants or tomatoes. All parts of the Paraguay nightshade plant are considered highly toxic to humans and pets.
Paraguay Nightshade Overview
Where to Plant Paraguay Nightshade
Plant Paraguay nightshade in a sunny location where it can spread. The fragrant, fast-growing shrub tends to be a pollinator magnet. So, plant it near a patio or outdoor gathering area to make the most of its light, but lovely perfume. Pair it with other long-blooming plants to create a garden bed that is alive with color for months at a time.
Paraguay nightshade makes a great complement to a mixed garden border. It can also be grown as a hedge or wall-side border shrub. The flowering shrub can reach 10 to 12 feet tall in just 4 to 6 years when planted in full sun and well-drained soil. Avoid growing this shrub in areas where children play, since they may be tempted by the toxic red berries.
How and When to Plant Paraguay Nightshade
Plant Paraguay nightshade in the spring in well-drained soil. Dig a hole 2 to 3 times the size of the root ball and place your plant in the center of the hole. Backfill the hole with the displaced dirt, tamping down gently to remove air pockets.
Water well after planting. Continue watering regularly and deeply during the first growing season to encourage plants to develop a deep, extensive root system. Spread a 2-inch-thick layer of mulch around the base of the plant (avoiding the trunk) to prevent soil moisture loss.
If planting more than one Paraguay nightshade plant, place them 6 to 10 feet apart. Place them slightly closer if growing a hedge.
Paraguay Nightshade Care Tips
Native to Brazil, Bolivia, and Argentina, this shrub will bloom all year long in warmer climates. The small blue flowers are followed by scarlet berries. In cooler regions, Paraguay nightshade can be grown outside in a container and then brought inside before the first frost. Flowers will appear in summer and fall.
Light
Paraguay nightshade thrives in full sun. In partial sun or shady locations, it may grow leggy or produce fewer flowers.
Soil and Water
Paraguay nightshade is not picky about soil pH but prefers moist, fertile, well-drained soils. It does not tolerate drought well, so make sure it gets about one inch of water a week. More water is necessary during extreme heat.
Temperature and Humidity
Paraguay nightshade prefers moderate humidity and temperatures between 65˚ and 100˚ Fahrenheit. It is not cold hardy and fares best if winter temperatures stay above 50˚. Prolonged exposure to cool temperatures will cause the shrub to reduce flowering, drop leaves, and go dormant.
Fertilizer
During the growing season, fertilize your established Paraguay nightshade shrub every 3 to 6 weeks with a liquid fertilizer. Or, if you prefer, use a granular, slow-release fertilizer every 3 to 4 months. Look for one that is low in nitrogen and higher in phosphorus (5-10-10 or 5-10-5) to encourage flowering. If you live in a cooler climate, decrease or stop fertilization during the winter months.
Pruning
Deadhead spent blooms throughout the growing season to encourage more flowering. Remove dead and diseased branches as necessary. To maintain or change the shape of your Paraguay nightshade, wait until at least the fall (when flowering slows or stops). If major pruning is necessary, use sharp, sterile shears to prune your tree in winter before new growth begins. Avoid removing more than one-third of the shrub.
Potting and Repotting
Paraguay nightshade makes an excellent container plant—especially if you live in a cooler climate. Be sure to choose a large, deep container with ample drainage. Enjoy its bold purple blooms and delightful fragrance on a sunny patio or deck and then bring your shrub inside for the winter. In frost-free climates, Paraguay nightshade can remain outside year-round.
To plant Paraguay nightshade in a container, start with a layer of pebbles or broken pot shards for drainage. Fill your pot with a high-quality potting mix and evenly balance your shrub in the pot. Plan to water daily to ensure its water requirements are met. Mix a slow-release fertilizer into the soil in early spring to supply nutrients through summer.
The best time to pot or repot your Paraguay nightshade is in the spring. To repot, remove the plant from its container and soak the root ball. Replace the pebbles or pot shards and add a fresh layer of soil. Center the shrub in the pot and backfill the container with fresh soil, tamping down as you work. Water thoroughly. Plan to repot your Paraguay nightshade every 2 years or when it outgrows its container. If your shrub gets too large to repot, replace the top layers of soil every 2 years.
Overwintering
Paraguay nightshade will not tolerate frost and should be overwintered indoors in cooler climates. Prune in early winter and bring your shrub inside before temperatures drop below 45˚ Fahrenheit. Keep your Paraguay nightshade in a bright location that stays between 50˚ and 65˚ Fahrenheit. Do not fertilize, but keep the plant regularly watered. Do not allow the soil to dry out. Keep it evenly moist. Move your shrub outside once temperatures are consistently above 50˚.
Pests and Problems
In ideal growing conditions, Paraguay nightshade has few issues with pests and diseases. Otherwise, it is prone to occasional attacks from aphids, whiteflies, and spider mites.
Your plant may also suffer from gray mold, blight, stem rot, powdery mildew, and other fungal diseases—especially if overwatered or kept in soggy soil.
How to Propagate Paraguay Nightshade
The easiest way to propagate Paraguay nightshade is via cuttings taken in the summer or early fall. To prepare, water your shrub well 24 hours before taking a cutting. Look for a 4 to 6-inch semi-hardwood cutting and cut the stem below a leaf node.
Remove any leaves from the bottom of the cutting and dip it in rooting hormone powder. Plant the treated end in a 6-inch pot filled with moist, well-drained potting mix and tamp the soil down to secure the cutting. You can place 2 or 3 cuttings in the same container. Water deeply until the excess drains from the pot.
Place a clear plastic bag over the container and place it in a warm area with lots of indirect sunlight. Check daily and keep the soil evenly moist for 4 to 6 weeks or until your cuttings have formed roots. Once your cuttings have developed roots, remove the plastic bag. When the roots are approximately 1 inch long, transplant your cuttings into separate containers.
Types of Paraguay Nightshade
Paraguay Nightshade ‘Variegata’
The ‘Variegata’ cultivar of Paraguay nightshade features blue flowers and variegated gray-green foliage edged in creamy white.
Paraguay Nightshade ‘Alba’
Lycianthes rantonnetii 'Alba' is a white-flowering Paraguay nightshade cultivar. The white blooms occasionally bear irregular lavender or blue-violet stripes—which adds an element of surprise to every blossom.
Paraguay Nightshade ‘Royal Robe’
One of the most popular Paraguay nightshade cultivars, ‘Royal Robe’ features lush green foliage and bright purple flowers. It has a sprawling habit and can be trained as a vine or tree.
Companion Plants for Paraguay Nightshade
Black-Eyed Susan
Black-eyed Susan, a butterfly garden staple, comes in both annual and perennial varieties. Hardy in zones 3-11, the sunny daisy-like flowers need little care to flourish. Plus, they bloom from June to August and sometimes well into fall. Black-eyed Susan plants prefer full sun and moist to dry, well-draining soils. They are, however, equally at home in loam, clay, and sandy soils—any soil that isn't consistently soggy.
Perennial Salvia
Perennial salvia is a popular choice for cottage and coastal gardens. There are nearly 1,000 species of salvia worldwide, some of which are tall, sprawling shrub-like plants. These stately perennials make excellent garden bed companions for Paraguay nightshade. Plus, they are easy to grow, drought-tolerant, and deer-resistant. Salvias are also a great nectar source, so if you plant them, expect pollinators (especially hummingbirds) to visit your garden.
Spirea
Spirea (hardy in zones 5-10) is a diverse group of fast-growing shrubs that prefer full sun and moist, well-drained soil. It’s considered invasive in some parts of the Northeast and South, but in other areas it’s a pretty option for hedging and erosion control. Spirea japonica, the most common variety, bears pink flowers in early summer and foliage that softens from orange-gold to light green.
Tall Verbena
Tall verbena (Verbena bonariensis) is a tall, purple-blooming tender perennial that is hardy in zones 7-11. The prairie garden favorite happily reseeds—especially in mild climates—but is highly attractive to butterflies, bees, and other pollinators. Verbena plants prefer full sun and moist, well-drained soil. With proper placement and care, they’ll begin their flowery show weeks before other flowering plants and repeat the show in the fall.
Frequently Asked Questions
- How long do Paraguay nightshade plants live?With proper care and placement, most Paraguay nightshade plants live approximately 20 years.
With proper care and placement, most Paraguay nightshade plants live approximately 20 years.
- Why is my Paraguay nightshade plant dropping leaves?Paraguay nightshade shrubs will drop leaves if the weather is too cool or if they are not getting enough sun. If your plant is dropping leaves while in full sun (and the temperature is consistently above 60˚), it may be overwatered.
Paraguay nightshade shrubs will drop leaves if the weather is too cool or if they are not getting enough sun. If your plant is dropping leaves while in full sun (and the temperature is consistently above 60˚), it may be overwatered.