How to Grow Antirrhinums
from Seed in the UK
A complete cottage garden guide — from sowing those tiny seeds to months of spectacular, fragrant spires in every colour imaginable
Antirrhinums — or snapdragons as they're universally known and loved — are one of the great unsung heroes of the cottage garden. With their tall, densely packed flower spires in colours ranging from the palest ivory and soft apricot through to the most vivid crimson, magenta and deep burgundy, they bring a richness and verticality to a border that few other annuals can match. And of course, there's the irresistible squeeze — that distinctive snap of the dragon's mouth that has delighted children (and adults) for generations.
They have a slight reputation for being tricky from seed, which is almost entirely undeserved. Yes, they need a little more time and patience than a cosmos or a sunflower, but the process is completely manageable and the results are genuinely spectacular. This guide will take you through every step with all the reassurance and detail you need to grow a truly wonderful display.
Quick Facts at a Glance
Plant Type
Half-Hardy Annual/Short-lived Perennial
Sowing Time
Jan – March indoors
Flowering Months
June – October
Position
Full sun, well-drained
Eventual Height
20–120cm
Difficulty Rating
3 out of 5 — Moderate
Understanding Antirrhinums
Before we dive into sowing, it helps to understand what antirrhinums actually are — because they sit in an interesting botanical middle ground that affects how you grow them.
Half-Hardy Annual or Short-Lived Perennial?
Antirrhinums are technically short-lived perennials — in mild winters and sheltered spots they can survive and flower for a second or even third year. However, in most of the UK they are grown as half-hardy annuals, sown fresh each year for the best results. Second-year plants often become woody and flower less freely, so annual sowing is generally recommended for a really generous display.
Choosing Your Height
Antirrhinums come in a wide range of heights — dwarf varieties at 20–30cm are wonderful for the front of a border or containers, intermediate types at 45–60cm suit the middle of a mixed border beautifully, and tall varieties at 90–120cm make dramatic statement plants and superb cut flowers. Choose your variety according to where you want to use them — or grow a mix of heights for a really layered, cottage garden effect.
When & How to Sow
Antirrhinums need a long growing season to flower well — they are slow to get going compared to cosmos or sunflowers, and this is the main reason they're sown earlier than most half-hardy annuals. Starting in January or February gives them the time they need to develop into strong, floriferous plants by summer.
Sowing Window — January to March
Sow antirrhinums indoors from January onwards, ideally in a heated propagator or on a warm windowsill. Earlier sowings (January or February) will produce earlier, larger plants, though they'll need careful management indoors over a longer period. March sowings are perfectly adequate if you're newer to growing from seed and want a simpler process.
Antirrhinum seeds are tiny — they need light to germinate and should never be covered with compost.
Step by step:
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Use fine seed compost. Antirrhinum seeds are extremely small — almost dust-like — and need a fine, firm surface to germinate on. Use a dedicated seed compost rather than multi-purpose, and firm it gently before sowing. Fill trays or modules to within 1cm of the top.
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Water the compost before sowing. Water the compost thoroughly before you sow, then allow it to drain. Watering after sowing will wash the tiny seeds around and make even germination impossible.
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Sow on the surface — do not cover. This is the most important rule for antirrhinums: the seeds need light to germinate. Tip a small amount of seed into your palm and tap gently to scatter onto the compost surface as thinly as possible. Do not cover with compost or vermiculite.
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Cover with a clear lid or cling film. Place a propagator lid or loosely draped cling film over the tray to retain humidity. This is important during germination — without it, the tiny surface-sown seeds can dry out very quickly.
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Place in warmth and light. Antirrhinums germinate best at around 18–21°C and need light even at the germination stage. A warm, bright windowsill or heated propagator is ideal. A dark airing cupboard will not work — move to light immediately if using one for initial warmth.
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Be patient. Germination typically takes one to three weeks. Keep the compost surface just moist — never soggy — and resist the urge to cover the seeds. Once you see tiny seedlings appearing, remove the propagator lid gradually to allow air circulation.
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Prick out when large enough to handle. When seedlings have two or three sets of true leaves, carefully prick them out into individual small pots or modules. Handle them by a leaf — never the stem — and pot into good peat-free multi-purpose compost.
Beginner's Reassurance
The trickiest part of growing antirrhinums from seed is their size — those tiny seeds feel alarmingly small and the seedlings that emerge are equally delicate. But once they've been pricked out and potted on, they grow with real vigour. Take care at the sowing and pricking out stage and the rest comes naturally.
Pinching Out the Growing Tip
Pinching out is absolutely essential for antirrhinums — perhaps more so than for any other flower in this guide. Without it, plants produce a single central spike and then largely stop. With it, they branch into a generous, multi-stemmed plant that produces flower spires continuously over a very long period. It is the single most transformative thing you can do.
A confident pinch at the right moment — the single most important step for a truly generous antirrhinum display.
When to pinch out: When young plants are around 8–10cm tall and have developed four to six pairs of leaves, pinch or snip out the growing tip — the very top of the main stem — just above a pair of leaves. This is usually done while plants are still in their pots indoors, before planting out.
What happens next: The plant responds by producing multiple side shoots from the leaf axils below the pinch point. These will each develop into a flowering stem, resulting in a plant with four, six or even more spires rather than just one. The display will be significantly longer, more abundant and more beautiful as a result.
Don't Be Nervous
Every gardener hesitates at this step the first time — snipping the top off a plant you've nursed from a tiny seed feels deeply wrong. But pinched antirrhinums are dramatically better than unpinched ones. Use sharp scissors, be decisive, and stand back over the coming weeks to watch the plant branch and fill out. You'll never skip this step again.
Pinch Twice for Maximum Branching
For an even more prolific display, consider pinching out a second time — once the side shoots that develop after the first pinch have themselves grown four to six pairs of leaves, pinch those tips too. This produces an even more branched, bushy plant. It adds two to three weeks to your growing timeline but gives a remarkably generous result, particularly for taller varieties grown as cut flowers.
Growing On Tips
Once pinched out and growing strongly, antirrhinums need hardening off carefully before planting out, and then relatively straightforward care through the season. Here is what to focus on.
Given sun, decent drainage and regular deadheading, antirrhinums will flower from early summer right into autumn.
Hardening Off
Antirrhinums are half-hardy and must be hardened off carefully before planting out. Bring pots outside for increasing periods over two to three weeks from mid-April, starting with sheltered daytime conditions and working up to leaving them out overnight. Don't rush this — a cold check can set plants back significantly and delay flowering.
Watering
Water regularly while establishing, particularly during dry spells in early summer. Once established, antirrhinums are reasonably drought-tolerant — they prefer well-drained soil and dislike sitting in wet conditions. Water at the base to avoid wetting the foliage, which can encourage fungal issues. During very hot, dry spells, deep watering every two to three days is ideal.
Feeding
Feed every two weeks with a high-potash liquid fertiliser — tomato feed is perfect — once flower buds begin to appear. This encourages continued flower production over a long season. Avoid high-nitrogen feeds which push leafy growth at the expense of flowers. A single balanced feed in early summer before flowering begins is also beneficial.
Deadheading
Remove spent flower spires by cutting back to a side shoot or bud — this is crucial for prolonging the display. Antirrhinums will naturally try to set seed once flowers fade, and deadheading redirects that energy into producing new spires. Cut back hard in midsummer if plants become straggly and they will reliably produce a fresh flush of growth and flowers for autumn.
The Midsummer Cut-Back
If your antirrhinums look tired or leggy by mid-July — which is common in a warm summer — don't be afraid to cut them back hard, reducing each stem by around a third to a half. Water well and give a high-potash feed. Within three to four weeks you'll see fresh growth emerging, and a wonderful second flush of flowers will carry you right through to the first frosts of autumn. This is one of the best-kept secrets of growing antirrhinums well.
Planting Out
Plant out after the last frost — from mid-May in most of the UK, though June is safer in exposed or northern gardens. Space plants according to variety: dwarf types at 15–20cm, intermediate at 25–30cm, and tall types at 35–45cm. Choose a position in full sun with well-drained soil — antirrhinums dislike heavy, waterlogged ground and will perform significantly better in a sunny spot.
Common Problems & How to Fix Them
Antirrhinums are generally robust once established, but there are a few things worth knowing about and watching for through the season.
| Problem | Likely Cause | What to Do |
|---|---|---|
| Poor germination | Seeds covered with compost, too dark, too cold | Antirrhinum seeds must not be covered — they need light to germinate. Ensure propagator or tray is in a bright position at 18–21°C. Use fresh seed where possible as viability decreases with age. |
| Leggy, weak seedlings | Insufficient light, too warm, overcrowded | Move to the brightest possible position immediately after germination. Thin or prick out promptly to avoid overcrowding. Pinching out will help produce bushier growth once plants are large enough. |
| Antirrhinum rust | Fungal disease — orange pustules on leaf undersides | This is the most common antirrhinum problem. Remove and dispose of affected leaves immediately — do not compost. Improve airflow around plants by spacing correctly. Choose rust-resistant varieties where possible. Avoid overhead watering. A copper-based fungicide can help in severe cases. |
| Powdery mildew | Dry at roots, poor airflow, warm nights | Water consistently at the base, improve spacing, and remove affected leaves. Most common in late summer — often appears after the main flush of flowers and rarely threatens plant health at that stage. |
| Aphids | Soft new growth, warm weather | Check growing tips and flower buds regularly. Knock off small colonies by hand or with a blast of water. Encourage natural predators. Avoid high-nitrogen feeding which produces soft, aphid-attractive growth. |
| Slugs & snails | Young transplants, moist conditions | Young plants are most vulnerable at planting out. Use organic slug pellets, copper collars, or beer traps around new transplants. Once established and growing strongly, antirrhinums are much less susceptible. |
| Plants stop flowering early | Spent spires left to set seed, heat stress | Deadhead consistently — remove spent spires before seed pods form. If plants become very tired in midsummer, cut back hard and feed with high-potash fertiliser for a strong autumn flush. |
A Note on Antirrhinum Rust
Rust is the one disease antirrhinums are genuinely susceptible to, and it's worth knowing about before you grow them. It appears as orange or brown powdery pustules on the undersides of leaves and can spread quickly in warm, humid conditions. The best approach is prevention — good spacing, avoiding overhead watering, and choosing rust-resistant varieties. Several modern varieties have been bred with strong rust resistance, and these are well worth seeking out if you've had problems in the past.
When to Expect Flowers
Antirrhinums sown in January or February will typically begin flowering from late May or June. March sowings will flower from July onwards. Once flowering begins and you keep on top of deadheading, the display will continue right through until the first hard frosts of autumn — often well into October. This exceptional season length is one of antirrhinums' greatest qualities and more than repays the extra effort of an early start.
Tall varieties grown as cut flowers will be at their peak in July and August. Dwarf and intermediate types are often at their most prolific in June and September, with a natural dip in the hottest part of midsummer — the cut-back technique described above helps bridge this gap beautifully.
From early summer to the first frosts — antirrhinums offer one of the longest flowering seasons of any cottage garden annual.
Overwintering for a Second Year
In mild areas or sheltered gardens, antirrhinums can survive winter and flower again the following year. If you want to try this, cut plants back hard in autumn, mulch the base with a thick layer of compost or straw, and leave them in situ. They won't always make it through a cold winter, so it's always worth sowing fresh seed too — but a successfully overwintered plant will flower earlier and more abundantly than any new seedling.
Cutting & Using as a Cut Flower
Tall antirrhinum varieties are superb cut flowers — among the best the cottage garden can produce. The long, elegant spires look wonderful in arrangements both formal and informal, and they last remarkably well in a vase.
For cutting fresh
Cut antirrhinum spires early in the morning when around a third to half of the florets on the stem are open — the remaining buds will continue to open in the vase, giving you a long-lasting display. Cut right back to where the stem meets a side shoot, using sharp scissors or snips. Place immediately into deep, cool water and allow to condition for a few hours in a cool spot before arranging.
Antirrhinums are excellent vase flowers — expect eight to twelve days of enjoyment from a well-conditioned stem, making them exceptional value compared to many cut flowers. Change the water every two days and recut stems at an angle to extend vase life further.
Good for Cutting?
Absolutely — tall antirrhinums are among the finest cut flowers available to UK cottage gardeners. The range of colours is extraordinary, the stems are long and strong, and they last beautifully in a vase. If you're planning a cutting garden, a row of tall antirrhinums is a non-negotiable addition. For the best cutting results, choose taller varieties specifically bred for stem length and grow them in a dedicated cutting patch where you can harvest freely without worrying about the border display.
Saving seed
Antirrhinums will set seed freely if a few spent spires are left on the plant. The seed pods are distinctive — small, papery capsules with holes at the top that look rather like tiny skulls (the botanical name Antirrhinum means "nose-like", though the seed pods have their own grim charm). Allow pods to ripen fully and turn brown before collecting — cut on a dry day, tip seeds into an envelope and store in a cool, dry place. Note that modern F1 hybrid varieties will not come true from seed, so seed saving is best done from open-pollinated varieties.
For Pollinators
Antirrhinums are excellent for bumblebees — the flower's distinctive snap mechanism means only bees heavy enough to push open the petals can access the nectar inside, making them a particularly valuable and efficient pollinator plant. Bumblebees of all species visit them enthusiastically throughout the summer, and a border of antirrhinums in full flower is a genuinely wonderful thing to watch on a warm summer afternoon.
Ready to grow your own spectacular antirrhinums?
We've chosen our antirrhinum seeds with the cottage gardener firmly in mind — selecting varieties that offer exceptional colour, strong performance in the UK climate, and the kind of generous, long-lasting display that makes all the effort of an early start entirely worthwhile. From towering cut flower varieties to compact, container-perfect dwarfs, we'd love to help you find the right antirrhinums for your garden. Browse our full range and get sowing — the season ahead will be all the more colourful for it.
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