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, where it earned the name Cape jewels for its bright, two-lipped blooms. It belongs to the figwort family and stays small, just 6 to 12 inches tall, which makes it a natural for the front of a bed, a window box, or a spilling container. The flowers come in nearly every color and keep coming as long as the weather stays mild.
It is grown as a cool-season annual, and that one fact shapes everything else. Set out around the last frost, it blooms from spring into early summer, then fades when the heat arrives. In mild-summer regions it can carry on, and in hot ones it does best as a spring or fall plant.
Nemesia asks little once it is settled in the right spot. Give it full sun, rich soil, and even moisture, pinch it young so it bushes out, and deadhead the spent flowers, and it rewards you with a long, generous run of bloom.
Care
The short version: full sun and cool weather, evenly moist but well-drained soil rich in organic matter, a balanced feed during the growing season, and a pinch when young to keep it bushy.
Light
Nemesia flowers best in full sun, though a little afternoon shade is welcome where summers run hot. Too much shade thins the bloom and leaves the plant leggy.
Water
Keep the soil evenly moist but never soggy, watering every 2 to 4 days and more often in heat. Water at the base and keep the leaves dry, since wet foliage invites powdery mildew.
Soil
Plant in humusy, well-drained soil that is loamy or sandy and rich in organic matter. Nemesia is easygoing about pH and takes anything from 6.0 to 8.0, but it will not stand for wet feet.
Temperature
This is a cool-weather plant happiest between 39°F and 75°F (4°C to 24°C). It shrugs off light cold but flags badly once the days turn hot and the nights stay warm.
Humidity
Ordinary outdoor humidity suits it fine, so there is no number to chase. What matters far more is air movement, since still, damp air around crowded plants is what brings on mildew.
Feeding
Feed with a balanced fertilizer monthly through the growing season to keep the bloom going. If the leaves yellow or take on a purple cast, that is a cue to feed.
Pruning
Pinch the growing tips once or twice while the plant is young so it fills out instead of stretching, and deadhead spent flowers to keep new ones coming. When bloom slows or heat sets in, cut the plant back by a third to a half to spark fresh growth.
Size & spacing
Nemesia stays compact at 6 to 12 inches (15 to 30 cm) tall and about as wide. Give each plant 6 to 12 inches (15 to 30 cm) of room so air moves freely and mildew stays away.
When to plant
Nemesia runs on cool weather and bows out when summer turns hot. Start the seed indoors in late winter, set the plants out around your last frost, and enjoy the flowers 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 back to one thing: heat or water out of balance. Watch the whole plant in summer and the leaves the rest of the time. Match what you see below and act while it still helps.
Plants flop over with soft, rotted roots
Soggy ground that never drains brings on root rot, and the roots turn brown and mushy. There is no saving badly rotted plants, so lift the healthy ones and replant them in soil worked with compost. Going forward, water only when the plant needs it and let the ground breathe between drinks.
Fix:
- Improve drainage with organic matter
- Avoid overwatering
- Replant healthy plants in well-drained soil
Plant wilts and quits blooming once summer turns hot
Nemesia is a cool-season plant, and a stretch of hot, humid days with warm nights pushes it into decline. Move it into afternoon shade, keep the soil evenly moist, and cut the plant back by a third to a half to coax fresh growth. Often it bounces back once the weather cools again.
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 dusty white film coating the leaves
Those dusty white patches are powdery mildew, which takes hold when the foliage stays wet and the air sits still. Water at the soil line so the leaves stay dry, and give each plant room for air to move through. A spray of neem oil clears up a stubborn case.
Fix:
- Water at the soil line and keep foliage dry
- Improve spacing and air circulation
- Apply neem oil if needed
Twisted new growth with a sticky or speckled look
Curled tips, sticky honeydew, or silvery stippling point to aphids or thrips feeding on the soft growth. A blast of water knocks back a light infestation, and insecticidal soap or neem oil handles a heavier one. Check the plants every few days so you catch the pests early.
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 you can grow it in a bed your cat, dog, or rabbit can reach without worry.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Nemesia is safe around cats, and a curious nibble won't poison one. A big mouthful of any plant can still leave a cat with a passing upset stomach.
Dogs None
Dogs can share a garden bed of nemesia with no worry, since none of the plant is toxic to them. The worst a chewed stem usually brings is a bit of drool or mild tummy trouble from the roughage.
Horses Safe
Nemesia carries no known toxins for horses and is fine to have where they graze.
Rabbits Safe
Rabbits can browse nemesia safely, and the plant holds nothing that would harm them.
Livestock Safe
Cattle, goats, and sheep face no danger from nemesia in or near their pasture.
Birds Safe
The plant poses no threat to birds, whether they peck at the seed or the foliage.
People Safe
Nemesia is grown for show, not the table, but it isn't poisonous and a curious child who tastes a flower comes to no harm.
Varieties
Nemesia comes in many named strains, mostly sorted by height and color. These few turn up often and are worth knowing.
Blue Gem
A compact strain reaching only 6 to 9 inches with clear, true-blue flowers.
Carnival
A bushier plant at 9 to 12 inches that blooms in a bright mix of colors.
Triumph
A dwarf strain sold as a mixed-color blend for tight spaces and edging.
How to propagate
Nemesia is easy to multiply, whether you sow a packet of seed in late winter or root a few 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 grow nemesia. Start it indoors 8 to 10 weeks before your last frost or sow it outside in spring, and because the seed needs darkness, cover it lightly and keep it moist. Sprouts show in 1 to 2 weeks, and flowers follow within a couple of months.
Stem cuttingsModerate
Take soft-stem cuttings in summer. · Roots form in about 4 to 6 weeks.
You can also clone a plant you like from cuttings, though it takes more patience. Take 4 inch soft-stem cuttings in summer, dip them in rooting hormone, and keep them moist while roots take hold 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 from southern Africa, but almost no garden treats it that way. It rarely lives 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 sulks in hot, humid days and warm nights. Summer heat often kills it back unless you cut it down and give it afternoon shade to ride out the worst of it.