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Repotting guide

When & how to repot Snapdragon (Antirrhinum majus)

Also called snap, dragon flower.

About Snapdragon

Antirrhinum majus · also called snap, dragon flower · flowering

Snapdragons are cool-season annuals with spires of dragon-mouth flowers in every colour. Self-seed in mild gardens and reseed reliably. Pinch when young for branching. Pet-safe; non-toxic to cats and dogs.

Antirrhinum majus is a Mediterranean species in the Plantaginaceae, a tender short-lived perennial (USDA 7–10) almost always grown as a cool-season annual for its hooded, jaw-like flower spikes.

Grows in moderately fertile, well-drained soil; per RHS, sow seed at 16–18°C in late summer/early autumn and overwinter young plants under glass, or sow in early spring.

Mature size: 30-90 cm tall

Watch for — Rust on leaves: Orange spots; remove and choose rust-resistant varieties.

Sources: rhs.org.uk, plants.ces.ncsu.edu, extension.msstate.edu

How to tell snapdragon needs repotting

Repotting on a calendar is less reliable than reading the plant. For snapdragon, watch for these signs:

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot snapdragon

Pot on seedlings as they grow; not a perennial repot. Snapdragonis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Upright cool-season annual.

What size pot to step snapdragon up to

Pot snapdragon on gradually — a seedling jumped straight into a huge pot sits in cold, wet, airless soil and stalls. Step up one or two sizes at a time as the roots fill each container, finishing in a large final pot or the ground. The aim is roots that never circle and never check.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot snapdragon

Pot snapdragon on through the active growing season, whenever roots fill the current container — there is no single date, just "before it becomes root-bound". Avoid potting on during a cold snap.

Step-by-step: repotting snapdragon

  1. Pot on before it is root-bound. Check snapdragon regularly; move it up as soon as roots reach the edge of the cell or pot, not after they have circled.
  2. Step up one or two sizes. Choose the next container up — not a giant one. Cold, wet, unused soil around a small root system stalls seedlings.
  3. Knock it out gently. Support the stem, tip the pot, and ease the rootball out without breaking it. A little teasing of circled roots at the base is fine.
  4. Pot into rich mix. Set it into fresh free-draining loam at the same depth (tomatoes are the exception — they can go deeper to root along the stem).
  5. Water in and grow on. Water well, keep it in good light, and resume feeding once it is established and growing again.

Aftercare

Water snapdragon in well and keep it in bright light; a freshly potted-on seedling can wilt for a day while roots settle, so do not overcompensate by drowning it. Do not fertilise for about 1 week — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for snapdragon

Snapdragon wants free-draining loam. pH 6.2-7.0. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting snapdragon — frequently asked questions

How often should you repot snapdragon?

Pot on seedlings as they grow; not a perennial repot for snapdragon. Snapdragon is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into free-draining loam so the roots never circle the cell, ending in a large final container. A root-bound transplant stalls and never fully recovers.

What size pot does snapdragon need?

Pot snapdragon on gradually — a seedling jumped straight into a huge pot sits in cold, wet, airless soil and stalls. Step up one or two sizes at a time as the roots fill each container, finishing in a large final pot or the ground. The aim is roots that never circle and never check. Use our pot size calculator to size it from the plant's current pot and root spread.

When is the best time of year to repot snapdragon?

Pot snapdragon on through the active growing season, whenever roots fill the current container — there is no single date, just "before it becomes root-bound". Avoid potting on during a cold snap.

Can you put snapdragon straight into a much bigger pot?

No. Even a fast-growing snapdragon should only go up one pot size at a time. A vastly oversized pot holds a reservoir of wet soil the roots cannot reach, which stays cold and soggy and rots the roots — the opposite of what you wanted.

Should you fertilise snapdragon after repotting?

Not immediately. Wait about 1 week after repotting snapdragon. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.

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