How to Grow Antirrhinum
'Black Prince' from Seed
An heirloom snapdragon in crimson so deep it reads almost black, over bronze-purple leaves. Dark from the ground up, and one of the most dramatic flowers you can raise from seed.
'Black Prince' is a snapdragon for gardeners who like their borders moody. The flowers are a deep, velvety crimson, and the leaves and stems behind them are bronze-purple, so the whole plant is dark. In low evening light the spikes look close to black.
It is an old variety, and it grows like one. Seedlings are slower and less even than modern F1 bedding snapdragons, and plants vary a little in height. None of that makes it difficult. Sow it early under cover, pinch it once, and it will flower from June until the autumn.
Quick Facts at a Glance
Plant Type
Half-hardy annual
Sowing Time
Jan to Mar, under cover
Flowering
June to September
Position
Full sun
Height
Around 45cm
Difficulty
2 out of 5, easy
Understanding the Plant
'Black Prince' is a variety of Antirrhinum majus, the common snapdragon. Snapdragons are short-lived perennials in their native Mediterranean, but in the UK they are grown as half-hardy annuals, sown early under cover and planted out once the frosts have passed.
What sets 'Black Prince' apart is that the colour runs right through the plant. Most red snapdragons have green leaves; this one has bronze-purple foliage and dark stems, which makes the crimson flowers look even deeper. Bumblebees are strong enough to prise the flowers open and visit them all summer.
Give dark flowers a light background
Very dark flowers soak up light and disappear against bare soil, a dark fence or a hedge. Plant 'Black Prince' in groups in front of something pale, such as silver foliage, white cosmos or a light wall, and the spikes will stand out clearly.
When & How to Sow
Snapdragon seed is very fine, almost dust-like, and needs light to germinate. Sow it early, from January to March, on a warm windowsill or in a heated propagator so the plants are a good size by planting-out time.
Mix fine seed with sand
Tip the seed into a pinch of dry silver sand and sprinkle the mixture over the tray. It spreads the seed more evenly, and you can see where it has landed.
Sow on the surface. Fill a tray with fine, damp seed compost, sprinkle the seed thinly over the top and press it in lightly. Do not cover it. Keep the tray at around 18 to 21°C under a clear lid, and expect seedlings in 10 to 21 days.
Prick out into modules. Once seedlings have their first true leaves, move them into individual cells and grow them on somewhere bright and cool. Warm, dim conditions make them stretch.
Pinch out, harden off and plant out. When plants have four or five pairs of leaves, nip out the growing tip to encourage side shoots. Harden off and plant out in April or May, once frosts have passed, 25 to 30cm apart.
Growing On Tips
Full sun
Plant somewhere sunny in well-drained soil. The darkest colour and sturdiest spikes come from plants in full sun.
Plant in groups
Set plants out in fives or sevens. A single dark snapdragon gets lost; a group reads as a deliberate patch of colour.
Cutting
Cut stems when the bottom third of the spike is open. The rest of the buds will open in the vase.
Deadhead spent spikes
Cut faded spikes back to a pair of leaves. Side shoots will follow with a second flush of smaller spikes.
Water at the base
Water in dry spells, aiming at the soil rather than the leaves. Wet foliage encourages rust, the main snapdragon disease.
Bumblebee favourite
Bumblebees are heavy enough to open the closed flowers and will work the spikes all summer.
Common Problems & How to Fix Them
| Problem | Likely Cause | What to Do |
|---|---|---|
| Orange-brown spots under leaves | Antirrhinum rust | Remove affected leaves straight away and pull badly affected plants. Water at the base, space plants well and avoid growing snapdragons in the same spot every year. |
| Seedlings collapse at soil level | Damping off | Use clean trays and fresh compost, water from below and give seedlings good airflow once they emerge. |
| Tall, weak seedlings | Too warm or too little light | Move seedlings to the brightest spot you have once they germinate, and grow them on cooler. |
| Plants of uneven height | Normal for an heirloom variety | Some variation is expected. Plant in informal groups rather than rows, where the difference looks natural. |
| Few side shoots | Growing tip not pinched | Pinch young plants at four or five pairs of leaves. Unpinched plants tend to produce one main spike and little else. |
When to Expect Flowers
Plants sown in January or February and planted out in spring usually start flowering in June. Cut or deadhead regularly and they carry on into September.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 🌱 Sow under cover | ||||||||||||
| 🪴 Plant out | ||||||||||||
| 🌸 Flowering |
Plant Specifications
The near-black heirloom snapdragon
Sow on the surface in late winter, pinch once and plant out after the frosts. You will have dark, velvety spikes from June into September.
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