Ornamental · Scrophulariaceae
Nemesia
Nemesia strumosa
Give it cool weather, steady moisture, and full sun, and nemesia floods a spring bed with color.
Full sun
Every 2–4 days
39–75°F · 4–24°C
USDA 2–11
Overview
Nemesia is a low, fast-growing flower from southern Africa, its bright, two-lipped blooms the reason it goes by Cape jewels. Each small flower splits into an upper and a lower lip above slender green stems, and the whole figwort-family plant holds to just 6 to 12 inches tall in a rounded, leafy tuft. The blooms open in nearly every color and keep unfurling as long as the weather stays mild.
It grows as a cool-season annual, and that trait runs through the plant from top to bottom. Set out around the last frost, the soft growth carries flowers from spring into early summer, then the stems tire once the heat arrives. Cool-summer regions keep the mound green and blooming longer, while hot ones see it at its fullest in spring or fall.
Once its roots take hold in the right spot, nemesia needs little from a grower. Full sun, rich soil, and even moisture keep the stems firm and the color coming, and a pinch of the young tips thickens the tuft while deadheading the spent, papery blooms draws out a long run of flower.
Care
The short version: full sun and cool weather, evenly moist but well-drained soil rich in organic matter, a balanced feed through the growing season, and a pinch of the young tips to build a dense, leafy mound.
Light
Nemesia opens the most flowers in full sun, though a little afternoon shade eases it where summers run hot. Deep shade thins the bloom and stretches the stems long and floppy instead of full.
Water
Keep the soil evenly moist but never soggy, watering every 2 to 4 days and more often in heat. Aim the water at the base and keep the leaves dry, since a wet leaf surface is where the white bloom of powdery mildew takes hold.
Soil
Plant it in humusy, well-drained soil that is loamy or sandy and rich in dark organic matter. The roots take any pH from 6.0 to 8.0, but they rot in soil that stays wet underfoot.
Temperature
This is a cool-weather plant, at its firmest and greenest between 39°F and 75°F (4°C to 24°C). The stems shrug off light cold but go slack once the days turn hot and the nights stay warm.
Humidity
Ordinary outdoor humidity suits it, so there is no number to chase. What counts far more is air moving through the leaves, since still, damp air around a crowded tuft is where the white mildew film settles.
Feeding
A balanced fertilizer monthly through the growing season keeps the flowers coming. Leaves that yellow or take on a purple cast are the plant's own signal that a feed is due.
Pruning
Pinch the soft growing tips once or twice while the plant is young so the tuft fills out instead of stretching, and pick off the spent, papery flowers to keep new buds forming. When bloom slows or heat sets in, shear the plant back by a third to a half to draw fresh green shoots from the base.
Size & spacing
Nemesia holds a compact, rounded shape at 6 to 12 inches (15 to 30 cm) tall and about as wide. Set each plant 6 to 12 inches (15 to 30 cm) apart so air threads between the leafy mounds and the mildew film stays off.
When to plant
Nemesia runs on cool weather and its soft growth gives out once summer turns hot. Start the fine seed indoors in late winter, set the young plants out around your last frost, and watch the flowers open from spring into early summer before the heat shuts them down.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Start seeds indoors 8 to 10 weeks before the last frost date.
- Plant: Set out seedlings or starter plants around the last frost date as a cool-season annual.
- Harvest: Blooms spring into early summer; in hot climates best in spring or fall, with summer heat causing dieback.
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Most nemesia trouble traces to one thing: heat, or water out of balance. The whole plant is the thing to watch in summer, when the stems can wilt fast, and the leaves the rest of the year. Match what you see below and act while it still helps.
Stems flop as the roots turn brown and soft
Soil that stays sodden and never drains brings on root rot, and the fine roots go brown, soft, and slippery to the touch. Plants rotted that deep cannot be saved, so lift the firm-rooted ones and set them into soil laced with compost. Watering only when the plant needs it, and letting the surface dry between times, keeps the roots pale and firm.
Fix:
- Improve drainage with organic matter
- Avoid overwatering
- Replant healthy plants in well-drained soil
Stems droop and the flowers thin out in the heat
Nemesia is a cool-season plant, and under hot, humid days and warm nights the soft stems go limp and the little blooms dwindle. Set it in afternoon shade, keep the soil evenly moist, and shear the plant back by a third to a half so fresh shoots break from the base. New green growth commonly pushes up again once the air cools.
Fix:
- Provide afternoon part shade
- Cut plants back by one-third to one-half to encourage new growth
- Keep soil evenly moist during heat
A chalky white dust settling over the leaves
The pale, floury coating filming the leaves and stems is powdery mildew, which spreads where the foliage stays damp and the air sits still. Directing water to the soil line leaves the leaf surfaces dry, and open spacing lets air slip past the leaves. A coat of neem oil clears the white film from a leaf that stays coated.
Fix:
- Water at the soil line and keep foliage dry
- Improve spacing and air circulation
- Apply neem oil if needed
New tips curl and the leaves turn sticky or speckled
Twisted, curling tips, a glossy film of sticky honeydew, or a fine silvery speckling across the leaf mean aphids or thrips are piercing the soft new growth. A hard jet of water knocks a light cluster off the stems, and insecticidal soap or neem oil clears a thicker one. A close look every few days spots the tiny insects while they are few.
Fix:
- Spray with insecticidal soap
- Apply neem oil
- Rinse off light infestations with water
Toxicity
Good news for pet owners and parents: nemesia is non-toxic to people and animals alike. The ASPCA does not list it among toxic plants, so its leaves, stems, and flowers are safe in a bed a cat, dog, or rabbit can reach.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Nemesia is safe around cats, and a curious nibble at a leaf or bloom will not poison one. A large mouthful of any plant can still leave a cat with a passing upset stomach.
Dogs None
Dogs take no harm from nemesia, since no part of the plant is toxic to them. A chewed stem tends to bring only a little drool or mild tummy trouble from the fibrous roughage.
Horses Safe
Nemesia carries no known toxins for horses and is safe growing where they graze.
Rabbits Safe
Rabbits can browse the leaves and stems of nemesia safely, as the plant holds nothing that harms them.
Livestock Safe
Cattle, goats, and sheep face no danger from nemesia in or near their pasture.
Birds Safe
The plant is no threat to birds that peck at the seed or the foliage.
People Safe
Nemesia is grown for its flowers rather than the table, but it is not poisonous, and a curious child who tastes a bloom comes to no harm.
Varieties
Nemesia comes in many named strains, sorted mostly by height and flower color. A few turn up often and are worth knowing by their look.
Blue Gem
A compact strain of just 6 to 9 inches carrying clear, true-blue flowers.
Carnival
A denser, bushier plant of 9 to 12 inches speckled with a bright mix of colors.
Triumph
A dwarf strain sold as a mixed-color blend, its low mounds suited to tight spaces and edging.
How to propagate
Nemesia is easy to multiply, whether you sow a scatter of its fine seed in late winter or root a few soft-stemmed cuttings off a plant you already grow.
SeedEasy
Start indoors 8 to 10 weeks before last frost, or sow outdoors in spring. · Germinates in roughly 1 to 2 weeks; flowering within a couple of months.
Seed is the usual way to raise nemesia from the ground up. Sow the fine seed indoors 8 to 10 weeks before your last frost or outdoors in spring, and because it sprouts in the dark, press it under a light scatter of soil and keep it moist. Green sprouts break the surface in 1 to 2 weeks, and the first flowers open within a couple of months.
Stem cuttingsModerate
Take soft-stem cuttings in summer. · Roots form in about 4 to 6 weeks.
A favorite plant can be copied from cuttings, which asks a little more patience. Snip 4 inch soft-stem cuttings in summer from the pliable green growth, dip the cut ends in rooting hormone, and keep them moist while white roots push out over the next 4 to 6 weeks.
Myths
Nemesia is a true perennial that comes back on its own every year.
It is a tender perennial native to southern Africa, though hardly any garden holds it as one. Its soft stems rarely last through a hot summer or a cold winter, so most gardeners replant it fresh each season and grow it as a cool-season annual.
Nemesia loves summer heat like most bedding annuals.
It is built for cool weather, and its tender growth wilts through hot, humid days and warm nights. Summer heat often burns it back to bare stems, unless a hard cut and afternoon shade carry it through the worst.