Planting Guide: How to Grow Snapdragons (Antirrhinum majus) from Seed
Snapdragon planting advice, step-by-step sowing guide, different varieties, and aftercare.
Flower Variety Identification
Common Name: Snapdragon
Scientific Name: Antirrhinum majus
Family: Plantaginaceae
When to plant Snapdragons in your climate
Not sure what your climate is? See our climate charts.
Cool: February, March, April, September, October, November, December
Temperate: February, March, April, May, September, October
Sub-Tropical: February, March, April, May, September, October
Tropical: March, April, May, June, July, August, September
Arid: April, May, June, July, August, September
Step by Step guide to growing Snapdragons
1. Choosing the Right Time to Plant
Snapdragons can be started indoors or sown directly in the garden, depending on your climate. For most regions, starting seeds indoors is the best option, as this gives the plants a head start before the warmer summer months.
When to plant:
- Indoor sowing: 8-10 weeks before the last expected frost.
- Outdoor sowing: Directly after the last frost when soil temperatures are consistently around 21-24°C.
2. Selecting the Ideal Location
Snapdragons thrive in full sun, needing at least 6 hours of direct sunlight per day. They also like well-drained, fertile soil. Avoid heavy clay soils, which can retain too much moisture and lead to root rot.
Location needs:
- Full sun (6 hours of direct sunlight).
- Well-drained, fertile soil rich in organic matter.
- Avoid heavy, compacted, or waterlogged soils.
3. Preparing the Soil
Preparing the soil is key to healthy snapdragon growth. I’ve grown Snapdragons in pretty terrible soil but they quickly became ‘rusted’. Fixing the soil with compost is really important.
Steps for soil preparation:
- Clear the planting area of weeds, rocks, and debris.
- Loosen the soil to a depth of about 20cm.
- Mix in compost to improve the soil
4. Sowing Snapdragon Seeds
Snapdragon seeds are some of the smallest seeds I’ve ever seem and while they should germinate in you lightly cover them with soil it’s best to just lightly push them on top of the soil as they need light to germinate.
Greenhouse (indoor) sowing method:
- Fill seed trays or pots with a light, well-draining seed-starting mix.
- Sprinkle the seeds on top of the soil surface and press them down gently. Try your hardest to get one seed per tray although you can always thin out when they sprout.
- Mist the soil with water to keep it moist, and cover the trays with plastic wrap or a humidity dome to retain moisture.
- Place the trays in a warm, bright location.
- Germination usually occurs within 14-21 days.
Direct sowing method:
- After the last frost, prepare the outdoor area by loosening the soil and removing any weeds. I always like to cover the area with a weed mat for 2 weeks prior to sowing.
- Scatter the seeds evenly on the soil surface and lightly press them down. If you have a large area, find something flat to lightly push on the surface. I use a large shovel.
- Water gently to settle the soil and keep it consistently moist until germination occurs.
5. Watering and Care During Germination
Consistent moisture is the most important thing during the germination stage.
Watering tips:
- Keep the soil moist but not soggy during germination.
- Once seedlings emerge, reduce watering frequency, allowing the soil to dry slightly between waterings.
6. Transplanting Seedlings Outdoors
If you started Snapdragon seeds indoors, you can transplant seedlings outdoors once they have developed a few sets of true leaves and the danger of frost has passed.
Transplanting tips:
- Harden off the seedlings by gradually exposing them to outdoor conditions over a week. This means exposing them to the outside for an additional hour everyday until they are able to spend all day outside.
- Space plants 15-30cm apart, depending on the variety, but make sure they have enough room for air circulation. If they don’t they may develop ‘rust’ which you can read about below.
- Water the transplants thoroughly after planting.
Three Growing Tips
1. Pinching for Bushiness:
To encourage bushier growth, pinch back the tips of young seedlings when they reach about 15cm in height. This promotes more branches and more flowers.
2. Deadheading for Continuous flowers:
Regularly deadhead old flowers to encourage snapdragons to produce more blooms throughout the season. This practice can also help keep the plants looking tidy.
3. Fertilising for Optimal Growth:
Snapdragons benefit from a balanced fertiliser applied every 4-6 weeks during the growing season. A fertiliser high in phosphorus can promote more blooms.
Different Kinds of Snapdragons
Antirrhinum majus (Common Snapdragon):
This is the most widely recognized variety, available in many colours and heights. Common snapdragons typically grow between 30-100cm tall and are perfect for borders and cutting gardens.
Antirrhinum molle (Rock Snapdragon):
A smaller variety, rock snapdragons reach about 30-60cm in height and produce delicate, tubular flowers. This species is often used in rock gardens and as ground cover.
Antirrhinum pacificus (Pacific Snapdragon):
Known for its vibrant colours and long-lasting blooms, the Pacific snapdragon can grow 30-90cm tall. This variety is perfect for attracting pollinators and is often used in cottage gardens.
Common Diseases and Pests
Snapdragons can face several diseases and pests, though many can be managed with proper care and attention. Here are some common issues to watch out for:
Powdery Mildew:
This fungal disease appears as a white, powdery coating on leaves, especially in humid conditions. Improve air circulation around plants and avoid overhead watering to reduce humidity.
Botrytis Blight (Gray Mould):
This disease causes wilting and browning of flowers and foliage, particularly in damp conditions. Ensure proper spacing between plants and promptly remove any infected plant material.
Aphids:
These small, sap-sucking insects can cluster on new growth and weaken the plants. Control aphids by spraying them off with a strong stream of water or using insecticidal soap.
Spider Mites:
In hot, dry conditions, spider mites may infest snapdragons, causing stippling and yellowing of leaves. Increase humidity around the plants by misting or using insecticidal soap for control.
Slugs and Snails:
These pests can damage young plants by feeding on tender leaves. Handpicking and using barriers like copper tape or diatomaceous earth can help control these pests.
Aftercare For Snapdragons
Once established, snapdragons require minimal maintenance, but a few key aftercare practices will help keep your plants healthy and blooming.
Mulching:
Apply a layer of organic mulch around the base of the plants to help retain moisture, suppress weeds, and maintain a more consistent soil temperature.
Fertilising:
Fertilise snapdragons every 4-6 weeks with a balanced fertiliser to promote healthy growth and abundant blooms. Avoid over-fertilization, as this can lead to leggy growth.
Pruning:
Regularly deadhead flowers to encourage continuous flowering. In late fall, after the first frost, cut back the plants to the ground to prepare them for winter.
Winter Care:
In colder climates, snapdragons may not survive the winter, as they are generally grown as annuals. In cooler regions, apply a layer of mulch around the base of the plants to protect the roots during winter.