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, and those bright, two-lipped blooms are why folks call it Cape jewels. It's part of the figwort family and stays small, just 6 to 12 inches tall, so it's a natural at the front of a bed, in a window box, or spilling over the edge of a pot. And the flowers? They come in just about every color and keep coming as long as the weather stays mild.
The big thing to know is that it's a cool-season annual, and honestly that one fact explains everything else. Pop it out around the last frost and it flowers from spring into early summer, then it fades once the heat shows up. Where summers stay mild it'll keep on going, and in hot spots it does best as a spring or fall plant.
Once it's happy in the right spot, nemesia doesn't ask for much at all. Give it full sun, rich soil, and even moisture, pinch it while it's young so it bushes out, snip off the spent flowers, and it'll pay you back with a long, generous run of bloom.
Care
The short version: full sun and cool weather, soil that's evenly moist but well-drained and rich in organic matter, a balanced feed through the growing season, and a pinch while it's young to keep it bushy.
Light
Nemesia flowers best in full sun, though a bit of afternoon shade is welcome where summers get hot. Give it too much shade, though, and the blooms thin out while the plant goes leggy.
Water
Keep the soil evenly moist but never soggy, watering every 2 to 4 days, and more often when it's hot. Water at the base and keep the leaves dry, because wet foliage is basically an invitation for powdery mildew.
Soil
Plant it in humusy, well-drained soil that's loamy or sandy and rich in organic matter. It's pretty relaxed about pH and takes anything from 6.0 to 8.0, but it just won't put up with wet feet.
Temperature
This one's a cool-weather plant, happiest between 39°F and 75°F (4°C to 24°C). It shrugs off a little cold no problem, but it really flags once the days turn hot and the nights stay warm.
Humidity
Regular outdoor humidity suits it just fine, so there's no number to fuss over. What matters way more is air movement, since still, damp air around crowded plants is what brings on mildew.
Feeding
Give it a balanced fertilizer monthly through the growing season to keep the blooms coming. And if the leaves yellow or take on a purple tint? That's your cue to feed.
Pruning
Pinch the growing tips once or twice while it's young so it fills out instead of stretching, and deadhead the spent flowers to keep new ones coming. When bloom slows or the heat kicks in, cut it 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 taps out once summer turns hot, so timing is everything. Start the seed indoors in late winter, set the plants out around your last frost, and you'll get 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 comes down to one of two things: heat, or water that's out of whack. Keep an eye on the whole plant in summer and on the leaves the rest of the year. Find what matches below, and act while it still does some good.
Plants keeling over with soft, rotted roots
When the ground stays soggy and won't drain, you get root rot, and the roots go brown and mushy. Can you save a badly rotted plant? Not really, so pull the healthy ones and tuck them into soil mixed with compost. After that, just water when the plant actually wants it and let the ground dry out a bit in between.
Fix:
- Improve drainage with organic matter
- Avoid overwatering
- Replant healthy plants in well-drained soil
Wilting and no more flowers once summer gets hot
Here is the thing: nemesia is a cool-season plant, so a run of hot, humid days with warm nights just wears it down. Slide it into afternoon shade, keep the soil evenly moist, and trim it back by a third to a half to wake up new growth. Give it time, because it'll often bounce back once things cool off.
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 whitish, dusty coating on the leaves
That chalky white stuff? It's powdery mildew, and it shows up when the leaves stay wet and the air isn't moving. Just water at the soil line so the foliage stays dry, and leave the plants enough space for a breeze to slip through. If a spot won't quit, a little neem oil sorts it out.
Fix:
- Water at the soil line and keep foliage dry
- Improve spacing and air circulation
- Apply neem oil if needed
Twisted new growth that's sticky or speckled
Curled tips, a sticky honeydew film, or fine silvery speckling usually mean aphids or thrips are munching the tender growth. A good blast of water clears out a light crowd, and insecticidal soap or neem oil handles a bigger one. Peek at the plants every few days and you'll catch these guys before they settle in.
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 doesn't list it among toxic plants, so you can grow it in a bed your cat, dog, or rabbit can get to without worrying.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Got a cat? No problem, because nemesia is safe and a curious nibble won't poison one. If a cat wolfs down a big mouthful of any plant, though, it might get a passing upset stomach.
Dogs None
A dog can hang out in a bed of nemesia with zero worry, since none of it is toxic to them. The worst a chewed stem usually does is bring on a little drool or mild tummy trouble from all that roughage.
Horses Safe
Nemesia has no known toxins for horses, so it's totally fine growing where they graze.
Rabbits Safe
Rabbits can nibble nemesia all they like, because there's nothing in it that would hurt them.
Livestock Safe
Cattle, goats, and sheep are perfectly fine around nemesia, whether it's in or near their pasture.
Birds Safe
Birds are safe with it too, whether they're pecking at the seed or the leaves.
People Safe
Nemesia is grown for looks, not for eating, but it isn't poisonous, so a curious kid who tastes a flower will be just fine.
Varieties
Nemesia comes in loads of named strains, mostly split up by height and color. Here are a few that pop up all the time and are worth knowing.
Blue Gem
It's a compact little thing at just 6 to 9 inches, with clear, true-blue flowers.
Carnival
It's a bushier pick at 9 to 12 inches that flowers in a bright jumble of colors.
Triumph
It's a dwarf strain sold as a mixed-color blend, great for tight spots and edging.
How to propagate
Nemesia is a breeze to multiply, whether you sow a packet of seed in late winter or root a few cuttings off a plant you've already got.
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 go-to way to grow nemesia, and it's easy. Start it indoors 8 to 10 weeks before your last frost or scatter it outside in spring, and since the seed needs darkness to sprout, just cover it lightly and keep it moist. You'll see sprouts in 1 to 2 weeks, and flowers show up within a couple of months.
Stem cuttingsModerate
Take soft-stem cuttings in summer. · Roots form in about 4 to 6 weeks.
Want an exact copy of a plant you love? You can clone it from cuttings, though it takes a bit more patience. Snip 4 inch soft-stem cuttings in summer, dip them 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.
Sure, it's technically a tender perennial from southern Africa, but almost nobody's garden treats it that way. It hardly ever lives through a hot summer or a cold winter, so most folks just replant it fresh each season and grow it as a cool-season annual.
Nemesia loves summer heat like most bedding annuals.
Nope, it's a cool-weather plant, and it really sulks through hot, humid days and warm nights. Summer heat often kills it back, unless you cut it down and give it some afternoon shade to ride out the worst of it.