How to Plant and Grow Solanum

Solanum is the largest genus in the nightshade family, which includes both edibles such as potatoes, peppers, and eggplants as well as ornamentals with flowers ranging from white to lavender and deep purple. Many species have a long bloom period during which they produce an almost non-stop flush of petite, fragrant blossoms. The vines are perennial and semi-evergreen in climates with mild winters and grown as annuals in cold regions.

All Solanum species are toxic to humans and pets.

Where to Plant Solanum

Choose a location with full sun or partial shade and well-drained, neutral to alkaline soil.

Plant solanum vines at the base of a sturdy trellis and it will quickly scramble toward the sky. It pretties up fences and brings walls to life with its flowers and foliage. Many types of solanum are semi-evergreen and will add interest nearly year-round. Solanum tolerates part shade, making it useful in the dappled light of a patio. Tie it to a post of an arbor or pergola to encourage it to climb where it will provide additional shade below the structure.

How and When to Plant Solanum

Plant solanum in the spring after all danger of frost has passed. When planting potted nursery plants, dig a hole about twice the diameter of the pot and about the same depth. Place the plant in the hole and fill in original soil to the top of the root ball. Gently tamp down the soil and water it well. Keep it watered in the absence of rain until the plant is established.

Spacing depends on the variety, ranging from as little as 3 feet for short vines to 12 feet for tall vines.

Solanum Care Tips

The plants in these species are generally low-maintenance and easy to grow.

Light

Solanum grows best in full sun or light shade. The light requirements may vary depending on the species; some are understory plants in their native habitat.

Soil and Water

The soil should be moist but well-drained, with a pH between 7.0 and 8.0.

Water the plant until it is established. After that, it withstands brief periods of drought; however, for continuous flowering, it is best to water the plant in dry spells.

Temperature and Humidity

Solanum are warm-weather plants that are easily damaged by frost. If you live in a cool climate, take your cues from tomatoes—the growing season of solanum is about the same. As tropical plants, solanum are usually tolerant of high humidity.

Fertilizer

Solanum has moderate fertilizer needs. Feeding it an all-purpose fertilizer twice during the growing season, once in the spring as the new growth starts, and again in early to midsummer, is sufficient. Avoid over-fertilizing the plant, which will lead to excessive vegetative growth.

Pruning

The primary goal of pruning solanum is to tame its size, and there is no hard-and-fast rule on when to prune it. If you grow it as a perennial, prune it in the fall when its growth starts to slow down. Alternatively, you can also prune it in the spring to make room for new, fresh growth.

Potting and Repotting Solanum

Smaller types of solanum make good container plants. Choose a pot at least 12 inches in diameter and make sure it has large drainage holes. Fill it with well-draining potting mix. Keep in mind that container plants need more frequent watering and fertilizer than inground plants.

When grown as an annual, it won’t require repotting during its single growing season. Otherwise, repotting to a larger container with fresh potting mix will be required when the roots outgrow the pot.

Pests and Problems 

Depending on the solanum species, you might encounter different pests and disease issues. Potato vine, for example, attracts aphids and red spider mites. Because solanum in the nightshade family, it is not unusual to find the same pests on the plants as on eggplant, namely flea beetles.

How to Propagate Solanum

Solanum seeds are not commonly available from seed companies. The plants can be propagated from stem cuttings or by layering. These vegetative propagation methods will only produce a new plant later in the season, therefore they make the most sense if you live in a warm climate; they do not work well for the short life cycle of solanum as an annual.

To propagate a solanum by layering, select a stem that is long enough to easily bend down to the ground. Remove all the leaves and entirely cover the stem with soil. Gently tamp down the soil and water it lightly. Keep the buried stem evenly moist at all times. After you see new growth emerging from the area, wait for more growth to appear before severing the stem from the mother plant with sharp pruners. Transplant it into a pot or to a new location in the garden.

Types of Solanum

Potato Vine

One of the most commonly grown ornamental solanum species is climbing nightshade (Solanum laxum), also called potato vine—not to be confused with sweet potato vine. With a height of 20 to 30 feet and 5 to 6 feet in width, this is no vine for small spaces. From summer to fall, it is covered with white, sweet-scented flowers. Zone 9-11

Paraguay Nightshade

Lycianthes rantonnetii (formerly Solanum rantonnetii) is a fast-growing upright evergreen shrub that reaches 6 to 8 feet in height and width. Paraguay nightshade has purple fragrant flowers with yellow centers from spring to fall. It is also grown as a small patio tree with a single trunk. A popular cultivar is 'Royal Robe'. Zone 9-11

Naranjilla

Known as naranjilla or lulo, Solanum quitoense is a shrub native to Ecuador and Peru. The large velvety leaves have purple hairs and orange-yellow spines. The fragrant white flowers turn into fuzzy orange-colored edible with a citrus flavor. When grown as an annual, the plant grows about 3 feet tall. In a warm, tropical climate, it reaches 8 feet in height. Zone 10-12

Solanum Companion Plants

Castor Bean

Plant a castor bean and then stand back. This is one of the fastest-growing, giant annuals in the garden, rivaled only perhaps by giant sunflower. By midsummer, you'll have a huge (it can hit up to 20 feet) tropical plant sporting burgundy foliage. Be careful, though. The seeds are extremely toxic. Wait to plant it outdoors after all danger of frost has passed; castor bean hates cool weather and won't grow well until temperatures heat up in summer. Zone 9-11

Licorice Plant

The elegant, silvery licorice plant is so useful to set off colorful flowers and to add contrast to plantings where you want more than just a mass of green. It's especially good in containers, where you can admire it up close and show off its spreading habit to best effect. Technically a tropical shrub, licorice plant is usually grown as an annual in the United States. It does best in full sun and well-drained soil. Zone 9-11

Hibiscus

The big, colorful blooms on hibiscus plants contrast nicely with solanum's smaller flowers. If you live in a cooler area, try planting hardy hibiscus instead of tropical hibiscus. Plant in full sun and well-drained soil. Zone 9-11 for tropical hibiscus; Zone 4-9 for hardy hibiscus

Salvia

There are over 700 different species of salvia, so it shouldn't be tough to find one that works in your yard. These plants usually have dark purple or blue flowers, and grow over 5 feet tall (depending on the variety). Plant in full sun and well-drained soil. Zone 3-10

Lantana

When lantana blooms, it really puts on a show with clusters of flowers that can be purple, red, orange, white, pink, or yellow. Lantana can tolerate some of the hottest, driest spots in your yard, and like solanum, it'll also attract pollinators like hummingbirds and bees. Plant in full sun and well-drained soil. Zone 8-11