Repotting guide

When & how to repot Scarlet Giant Hyssop (Agastache coccinea)

Also called Scarlet Giant Hyssop, Red Giant Hyssop.

More about scarlet giant hyssop

About Scarlet Giant Hyssop

Agastache coccinea · also called Scarlet Giant Hyssop, Red Giant Hyssop · flowering

Scarlet Giant Hyssop is a striking North American perennial bearing vivid scarlet to orange tubular flower spikes from midsummer into autumn, irresistible to hummingbirds and long-tongued pollinators. More heat- and drought-tolerant than many Agastache species, it suits sunny, well-drained borders and xeriscape gardens. Often treated as a short-lived perennial or annual in cooler climates.

Mature size: 60–100 cm tall, 40–60 cm wide

Watch for — Root rot in wet or heavy soils: The most common cause of plant failure outside its natural range. Ensure sharp drainage before planting. Raise beds or add a generous layer of coarse grit. In clay soils, consider growing in large containers with a gritty mix.

How to tell scarlet giant hyssop needs repotting

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

Roots growing out of the drainage holes, or the rootball lifting the plant proud of the rim.
Soil that has shrunk away from the pot sides and no longer holds water.
The pot is unstable because the plant has grown top-heavy.
Old, compacted, broken-down mix that stays wet too long — for a succulent that is a rot risk, so refresh it even if the pot size is fine.

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 scarlet giant hyssop

Every 2–3 years, into bone-dry mix. Scarlet Giant Hyssop's growth habit — upright, clump-forming herbaceous perennial — sets the pace. Scarlet Giant Hyssop is a striking North American perennial bearing vivid scarlet to orange tubular flower spikes from midsummer into autumn, irresistible to hummingbirds and long-tongued pollinators. More heat- and drought-tolerant than many Agastache species, it suits sunny, well-drained borders and xeriscape gardens. Often treated as a short-lived perennial or annual in cooler climates.

What size pot to step scarlet giant hyssop up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Scarlet Giant Hyssop stores water and rots in a large pot of slow-drying soil. A tight terracotta pot that dries fast is far safer than a generous plastic one. Never up-pot a succulent by several sizes.

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 scarlet giant hyssop

Spring or summer, while scarlet giant hyssop is in active growth and warm, is best — roots recover fastest then, and the plant is not sitting in cool damp soil. Avoid repotting a succulent in winter dormancy.

Step-by-step: repotting scarlet giant hyssop

Repot dry. Do not water scarlet giant hyssop for several days first. Working with dry roots and dry mix dramatically lowers the rot risk for a succulent.
Pick a snug, fast-draining pot. Choose terracotta one size up at most, with a drainage hole. Have gritty sandy or gritty, sharply drained soil ready.
Tip it out and clean the roots. Slide the plant out, crumble off the old soil, and trim any black, mushy or dead roots with clean snips.
Pot into dry mix. Set scarlet giant hyssop at its original depth in dry gritty mix, firming gently. Do not bury the stem deeper than it was.
Wait a week before watering. Leave it completely dry and out of harsh sun for about 7 days so any damaged roots callus. Only then water lightly.

Aftercare

Keep scarlet giant hyssop completely dry and out of fierce sun for about a week so any nicked roots callus before they meet moisture; watering a freshly repotted succulent is the classic way to rot it. Then resume the normal lean, dry rhythm. Do not fertilise for about 3 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for scarlet giant hyssop

Scarlet Giant Hyssop wants sandy or gritty, sharply drained soil. Thrives in lean, dry, well-drained soils with pH 6.5–8.0. Mimics its native dry grassland and scrub habitat. Avoid heavy clay or organically rich soils that retain moisture. Incorporate grit when planting on heavier ground. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting scarlet giant hyssop — frequently asked questions

How often should you repot scarlet giant hyssop?

Every 2–3 years, into bone-dry mix for scarlet giant hyssop. Repot scarlet giant hyssop every 2–3 years into a snug pot of sandy or gritty, sharply drained soil, ideally in spring or summer. Let it sit in dry soil and do not water for about a week afterwards so any nicked roots can callus. Over-potting and watering straight away is what rots succulents.

What size pot does scarlet giant hyssop need?

When is the best time of year to repot scarlet giant hyssop?

Should you water scarlet giant hyssop after repotting?

No — not straight away. Repot scarlet giant hyssop into dry mix and wait about a week before the first watering so any damaged roots callus over. Watering a freshly repotted succulent is the single most common way to rot one.

Should you fertilise scarlet giant hyssop after repotting?

Not immediately. Wait about 3 weeks after repotting scarlet giant 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.