How to Grow Snapdragon Seeds

Grow Guide #2380
Family: Plantaginaceae
Binomial name: Antirhinum majus
Life Cycle: Perennial (usually grown as an annual)

This 'How to Grow' guide details everything a home gardener needs to know to plant, grow and care for Snapdragon (Antirhinum majus).

When to Sow Snapdragon Seeds

Snapdragon can be grown year-round in most climates. Avoid planting in extremely hot or cold weather which can affect germination and growth. Use the table below to identify the best time of year to sow snapdragon in your climate.

Preparation

Snapdragon plants are best grown in full sun or part shade. Choose a location that will receive at least 3 hours of full sun each day.

Snapdragon plants need a well drained soil enriched with plenty of organic matter. Prepare soil by weeding it thoroughly, digging it over to loosen it and adding aged animal manure or compost. Keep the area free of weeds until planting. Learn more about preparing soil for planting here.

Snapdragon plants can be grown in containers. If possible choose a variety that’s recommended for container growing. Use a good quality potting mix and make sure your container is large enough for mature plants; a minimum of 10 litres is recommended for snapdragon. During the growing season, keep in mind that container grown plants may need additional fertiliser to encourage healthy growth.

How to Sow Snapdragon Seeds

Snapdragon seeds can be sown directly into the garden OR seedlings can be raised in trays or other containers and transplanted to the garden once established.

Sow Direct

1. Sow seeds directly in the garden 3mm deep and 15-25cm apart.
2. Keep soil moist but never wet or dry.
3. Seeds should germinate in around 7-14 days at a soil temperature of 21-24°C.
4. Young seedlings will need protection from pests, pets and weather until they are established.

Raise Seedlings

1. Fill trays, punnets or jiffy pots with a good quality seed-raising mix, or use soil starter pellets.
2. Sow seeds 3mm deep.
3. Keep soil moist but never wet or dry.
4. Seeds should germinate in around 7-14 days at a soil temperature of 21-24°C.
5. Transplant seedlings to the garden once they have their first true leaves and are large enough to handle (usually 5-10cm tall).
6. Plant out, spacing plants 15-25cm apart.

Tip: Snapdragon seeds can also be sown in the less formal ‘scatter seed’ method. Simply roughen the soil, scatter seeds evenly over the surface, then smooth the soil over lightly to cover the seeds.

Tip: Snapdragon seeds are quite small. Handle them carefully to avoid them blowing away or being washed away. Mix seeds with sand or fine potting mix prior to sowing or use a seed dispenser, damp toothpick or tweezers to help space them evenly. Press lightly into the surface after sowing so that the seeds make good contact with the soil. Take extra care to make sure seeds and seedlings don’t dry out. Read more about sowing small seeds here.

Optional: In cool climates snapdragon seeds can be sown indoors 6 weeks before the last expected frost. Grow them in a warm position with plenty of natural light.

How to Grow Snapdragon

Snapdragon plants may need watering during the growing season. Water when the soil is dry about 5cm below the surface (test this by scratching away a little soil with your finger). Water deeply in the early morning or late afternoon. Avoid watering the leaves of plants to avoid fungal diseases. Learn more about watering here.

If soil was well prepared no extra fertiliser should be necessary. In poor soil or to give your plants an extra boost, application of a high-potassium fertiliser or one formulated for flowering plants can be beneficial:

• Apply slow release fertiliser at the recommended rate when transplanting or when seedlings are 5-10cm tall.
• Apply liquid fertiliser at the recommended rate and frequency while plants are fruiting or flowering.

Optional: To give plants room to grow, thin seedlings when they are large enough to handle. Pull out any weak or small seedlings so plants are spaced about 15-25cm apart.

Optional: Pinch out the growing tips of snapdragon plants to encourage denser growth with stronger stems and more flowers. Using sharp secateurs or snips remove the top set of leaves, cutting just above a set of lower leaves.

Snapdragon plants should flower in approximately 110-120 days.

Deadhead snapdragon flowers regularly during the growing season. Using sharp secateurs or snips cut fading or dead flowers off just above a set of leaves. Removing old flowers regularly will encourage plants to produce more flowers. Learn more about deadheading flowering plants here.

If growing snapdragon for cut flowers, use sharp snips or secateurs to cut the longest stems possible, removing the lower leaves and placing the stems immediately in a clean bucket of water. Learn more about cutting and conditioning homegrown flowers here.

If growing as a perennial: When plants have finished flowering prune them back to neaten them and encourage strong new growth. Using sharp secateurs or snips, cut individual stems just above a set of lower leaves.

Common Problems when Growing Snapdragon

Like all plants, snapdragon is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing snapdragon plants:

• 

  Aphids are small (2-4mm long) sap-sucking insects that congregate on the new shoots or the undersides of leaves. They can cause leaves to wilt or become discoloured, and also excrete honeydew which can attract ants and other insect pests. To manage aphids, remove them by spraying with a garden hose, apply a soap or alcohol spray, or encourage predatory insects to your garden. Read more about aphids here.
• 

  Grey mould (Botrytis sp.) is a fungal disease that causes flowers to become mouldy and fruit to rot. Spores are transported by wind and can survive in soil or on green waste. The fungus spreads most in cool, damp weather. Prune off affected flowers and fruit, water plants at soil level (not on leaves) and if necessary spray with an appropriate fungicide or homemade spray.
• 

  Downy mildew is a fungal disease that causes yellow to grey-brown patches on leaves, especially the undersides. Water plants at soil level (not on the leaves), remove and destroy affected leaves and do not overcrowd plants to ensure adequate air flow. If problems persist, spray with a homemade milk spray or fungicide.
• 

  Slugs and snails are molluscs that feed on tender leaves and shoots, mostly at night, leaving slimy trails behind them. Control them by removing their hiding places, keeping free range poultry, collecting them by torchlight or by placing traps. Read more about slugs and snails here.
• 

  Spider mites (Tetranychus urticae), also known as two spotted mites, are sap-sucking arachnids that cause dry, wilted or discoloured leaves. The undersides of leaves may feel dry and a little like fine sandpaper. Prune plants to allow good air flow or spray with eco-oil or wettable sulphur. Learn more about managing spider mites here.
• 

  Whitefly is a sap-sucking insect related to aphids. They are often found in large numbers on the underside of leaves and will swarm in clouds when disturbed. Plants may have yellowing leaves or may wilt, and growth will be slowed. Whitefly can be removed with a garden hose or sprayed with soap spray. Badly affected plants should be destroyed. Attracting beneficial insects that will prey on whitefly can be beneficial. Read more about managing whitefly here.