Repotting guide

When & how to repot Mexican Hyssop (Agastache mexicana)

Also called Mexican Hyssop, Mexican Giant Hyssop.

More about mexican hyssop

About Mexican Hyssop

Agastache mexicana · also called Mexican Hyssop, Mexican Giant Hyssop · herb

Mexican hyssop is an aromatic, mint-family perennial with lemon-mint-scented foliage and long-blooming spikes of pink to crimson tubular flowers that draw bees and hummingbirds. Used in Mexican herbal teas (toronjil), it is short-lived but easily renewed, drought-tolerant once established, and needs sharp drainage and full sun to flower and overwinter well.

Mature size: 60-120 cm tall and 30-45 cm wide.

Watch for — Winter root rot: Wet, heavy soil over winter is the main killer. Plant in sharply drained ground or raised beds and keep the crown dry; in cold regions overwinter cuttings as insurance.

How to tell mexican hyssop needs repotting

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

Roots circling the bottom of the module or pot, or poking out of the drainage holes.
The seedling dries out within a day and growth has visibly stalled.
Roots are white and matted in a tight spiral when you tip the plant out.
It has outgrown its current container for the stage of the season — pot mexican hyssop on before it becomes hard root-bound.

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 mexican hyssop

Pot on seedlings as they grow; not a perennial repot. Mexican Hyssopis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Upright, clump-forming aromatic perennial with square stems, ovate toothed leaves, and dense terminal spikes of tubular flowers from summer into autumn..

What size pot to step mexican hyssop up to

Pot mexican hyssop 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 mexican hyssop

Pot mexican hyssop 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 mexican hyssop

Pot on before it is root-bound. Check mexican hyssop regularly; move it up as soon as roots reach the edge of the cell or pot, not after they have circled.
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.
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.
Pot into rich mix. Set it into fresh free-draining, lean to average loam at the same depth (tomatoes are the exception — they can go deeper to root along the stem).
Water in and grow on. Water well, keep it in good light, and resume feeding once it is established and growing again.

Aftercare

Water mexican hyssop 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 mexican hyssop

Mexican Hyssop wants free-draining, lean to average loam. Demands sharp drainage; pH 6.0-7.5. Rich, heavy, or wet soils shorten its life and cause winter root rot. Add grit on clay and avoid mulching right up to the crown. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting mexican hyssop — frequently asked questions

How often should you repot mexican hyssop?

Pot on seedlings as they grow; not a perennial repot for mexican hyssop. Mexican Hyssop 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, lean to average 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 mexican hyssop need?

When is the best time of year to repot mexican hyssop?

Can you put mexican hyssop straight into a much bigger pot?

No. Even a fast-growing mexican hyssop 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 mexican hyssop after repotting?

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