Ornamental · Scrophulariaceae
Nemesia
Nemesia strumosa
Give it cool weather, steady moisture, and full sun, and nemesia will fill a spring bed with color for you.
Full sun
Every 2–4 days
39–75°F · 4–24°C
USDA 2–11
Overview
Nemesia is a low, quick-growing flower from southern Africa, where its bright, two-lipped blooms earned it the sweet name Cape jewels. A member of the figwort family, it stays small at just 6 to 12 inches tall, which makes it a happy choice for the front of a bed, a window box, or a container left to spill over. Its flowers come in nearly every color and keep on opening for as long as the weather stays kind.
The one thing to remember is that nemesia is a cool-season annual, and that single fact guides everything else you do. Set it out around the last frost and it blooms from spring into early summer, then eases off when the heat rolls in. Where summers are mild it can keep going, and in hot regions it is happiest as a spring or fall plant.
Once it has settled into the right spot, nemesia asks very little of you. Give it full sun, rich soil, and even moisture, pinch it while young so it grows full and bushy, snip away the spent flowers, and it will thank you with a long, generous show of bloom.
Care
The short version: give it full sun and cool weather, soil that stays evenly moist yet drains well and is rich in organic matter, a balanced feed through the growing season, and a gentle pinch when young to keep it full.
Light
Nemesia blooms most freely in full sun, though a touch of afternoon shade is a welcome kindness where summers run hot. Give it too much shade and the flowers thin out while the plant grows leggy, so aim for the brightest spot you can offer.
Water
Keep the soil evenly moist but never soggy, watering every 2 to 4 days and a little more often in the heat. Water down at the base and let the leaves stay dry, since damp foliage is what tempts powdery mildew in.
Soil
Settle it into humusy, well-drained soil that is loamy or sandy and rich in organic matter. Nemesia is easygoing about pH and is content anywhere from 6.0 to 8.0, but it truly will not tolerate wet feet.
Temperature
This is a cool-weather plant, happiest between 39°F and 75°F (4°C to 24°C). It takes light cold in stride but wilts once the days turn hot and the nights stay warm, so plan its season around the cooler months.
Humidity
Ordinary outdoor humidity suits it beautifully, so there is no number to worry about. What counts far more is good air movement, because still, damp air around crowded plants is what invites mildew.
Feeding
Offer a balanced fertilizer monthly through the growing season to keep the flowers coming. If the leaves turn yellow or take on a purple cast, treat it as a gentle sign the plant is ready for a feed.
Pruning
Pinch the growing tips once or twice while the plant is young so it fills out rather than stretches, and deadhead the spent flowers to keep new ones arriving. When bloom slows or the heat sets in, cut the plant back by a third to a half to coax fresh growth, and do not be shy about it.
Size & spacing
Nemesia stays neat and compact at 6 to 12 inches (15 to 30 cm) tall and about as wide. Leave each plant 6 to 12 inches (15 to 30 cm) of elbow room so air can move freely and mildew keeps its distance.
When to plant
Nemesia thrives on cool weather and gracefully bows out once summer heats up, so there is no need to fret over the timing. Start the seed indoors in late winter, move the plants outside around your last frost, and enjoy the flowers from spring into early summer before the heat calls a rest.
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
Almost every nemesia hiccup comes down to one of two things: heat, or water that is out of balance. Keep a friendly eye on the whole plant through summer and on the leaves the rest of the year. Find what matches below and act while a small nudge still does the trick.
Soft, dark roots and a plant that leans over
Ground that stays wet and never drains leads to root rot, leaving the roots brown and mushy. Badly rotted plants cannot be nursed back, so gently lift the healthy ones and settle them into soil worked with compost. From here on, water only when the plant truly needs it and let the ground dry a little between drinks, and you will steer clear of it.
Fix:
- Improve drainage with organic matter
- Avoid overwatering
- Replant healthy plants in well-drained soil
When the heat arrives and blooming slows, take heart
Nemesia is a cool-season plant, so a run of hot, humid days and warm nights simply wears it out. Nudge it into afternoon shade, keep the soil evenly moist, and trim it back by a third to a half to invite fresh growth. You have not lost it, and it often perks right back up once cooler weather returns.
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 soft white dusting on the leaves
That pale, powdery film is powdery mildew, and it settles in when the foliage stays damp and the air hangs still. The fix is gentle: water down at the soil line so the leaves stay dry, and leave each plant a little breathing room so air can drift through. If a patch lingers, a light spray of neem oil clears it up.
Fix:
- Water at the soil line and keep foliage dry
- Improve spacing and air circulation
- Apply neem oil if needed
Curled tips with a sticky or speckled surface
Twisted new tips, a sticky honeydew film, or fine silvery stippling mean aphids or thrips are feeding on the tender growth. Do not worry, a firm rinse of water knocks a light infestation right off, and insecticidal soap or neem oil handles a heavier one. A quick look every few days lets you catch them before they get comfortable.
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 plant it in a bed your cat, dog, or rabbit can reach and never give it a second thought.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
You can relax with a cat in the house, because nemesia is safe and a curious nibble will not poison one. A very large mouthful of any plant can still leave a cat with a passing upset stomach, which soon settles.
Dogs None
A dog is welcome to share a bed of nemesia, since no part of the plant is toxic to them. The most a chewed stem tends to bring is a little drool or mild tummy trouble from the extra roughage, and that passes on its own.
Horses Safe
Nemesia holds no known toxins for horses, so it is perfectly fine to have growing where they graze.
Rabbits Safe
Rabbits can browse nemesia without any worry, as the plant carries nothing that would harm them.
Livestock Safe
Cattle, goats, and sheep come to no harm from nemesia growing in or beside their pasture.
Birds Safe
Birds are safe around the plant too, whether they peck at the seed or nibble the leaves.
People Safe
Nemesia is grown for its flowers rather than the table, yet it is not poisonous, so a curious child who tastes a bloom will be just fine.
Varieties
Nemesia comes in plenty of named strains, sorted mostly by height and color. A few of them turn up again and again and are lovely to know.
Blue Gem
A tidy little strain that stays just 6 to 9 inches tall and opens clear, true-blue flowers.
Carnival
A fuller, bushier plant at 9 to 12 inches that cheers a bed with a bright mix of colors.
Triumph
A dwarf strain offered as a mixed-color blend, perfect for small pockets and edging.
How to propagate
Nemesia is a joy to multiply, whether you sow a packet of seed in late winter or root a few cuttings from a plant you already love.
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 friendliest way to raise nemesia, and it rarely disappoints. Sow it indoors 8 to 10 weeks before your last frost or scatter it outside in spring, and since the seed likes darkness to sprout, cover it lightly and keep it gently moist. Little seedlings appear in 1 to 2 weeks, with flowers following in a couple of months.
Stem cuttingsModerate
Take soft-stem cuttings in summer. · Roots form in about 4 to 6 weeks.
If a plant charms you, you can grow more from cuttings, and a little patience is all it asks. Snip 4 inch soft-stem cuttings in summer, dip the ends in rooting hormone, and keep them moist while roots settle in 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, but hardly any garden can keep it that way. It seldom survives a hot summer or a cold winter, so most gardeners simply plant it fresh each season and enjoy it as a cheerful cool-season annual.
Nemesia loves summer heat like most bedding annuals.
It is a cool-weather flower at heart and struggles through hot, humid days and warm nights. Summer heat often burns it back, but do not be discouraged, since a trim and a spot of afternoon shade help it ride out the worst.