Photo by Polly Nelson

Nemesia

By Polly Nelson  UCCE Master Gardener

Common Name: Nemesia

Scientific Name: Scrophulariaceae

Planting area: Sunset zone 14-24, some species 1-24

Size: 1-2' high, 1' wide

Bloom Season: Spring to summer

Exposure: Full sun

Pruning needs: Deadhead; annual cut-back to promote regrowth

Water needs: Moderate

Snapshot: Nemesia's colorful blossoms liven up containers, hanging baskets, annual beds, or rock garden plantings. It is a native of South Africa and it requires minimal attention when its sun, pruning and water needs are sufficiently met. 

Narrow green leaves support four-inch clusters of cup-shaped flowers which can last for months before fading. Blossom colors range from blue to pink and yellow. Some varieties are intensely fragrant.

Plant nemesia in well-drained, slightly acidic soil. Till the garden bed a week before planting packaged or saved seeds in the spring. Add compost to improve soil drainage and fertility. Smooth the soil and apply water to settle the soil. When ready to plant seeds, scatter seeds evenly over the prepared bed, then cover with a light layer of soil to provide the darkness required for germination. Water well and keep the soil moist, but not soggy. Expect to see sprouts in 5-10 days. Thin seedlings to 6 inches apart once they have developed their second set of leaves. Spread organic mulch to within 2 inches of each plant. Encourage branching by pinching back tips once or twice or more often as they grow.

Pruning needs are met by removing spent flower stalks. If blooms cease in the summer or the plant begins to die back, cut the entire plant back by one-third to one-half of its overall size. Aggressive pruning at this time allows the plant to develop new growth and possibly more blossoms.

Nemesia can be propagated by seed or cuttings. Seeds can be collected from plants in autumn when they have developed flat seed capsules. Soft-stem cuttings can be collected in summer. Cut a shoot of fresh new growth about 4 inches in length, just above a bud, then trim lower leaves. Dip in rooting hormone, then plant in moist potting soil. Expect good root development in four to six weeks.

Potential pests include powdery mildew, aphids, or thrips. Prevent powdery mildew by watering the soil near the roots and keeping the leaves as dry as possible. Insecticidal soap or neem oil can be used to treat insect pests. A balanced fertilizer can be applied if leaves begin to turn yellow or purple. 

How to find us:

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