Repotting guide

When & how to repot Good King Henry (Blitum bonus-henricus)

Also called Good King Henry, Mercury, Wild Spinach.

More about good king henry

About Good King Henry

Blitum bonus-henricus · also called Good King Henry, Mercury · herb

Good King Henry is an old-fashioned hardy perennial vegetable in the goosefoot family, grown for spinach-like leaves and asparagus-like spring shoots. Tolerant and long-lived, it thrives in rich, moist soil and part shade, cropping for years from one planting. Leaves contain oxalic acid, so they are best lightly cooked rather than eaten raw in quantity.

Mature size: 40-60 cm tall and 30-45 cm wide.

Watch for — Downy mildew and leaf spot: As a goosefoot relative it is prone to mildew and fungal spotting in damp, crowded sites. Space plants, improve airflow, and remove affected foliage.

How to tell good king henry needs repotting

Repotting on a calendar is less reliable than reading the plant. For good king henry, 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 good king henry 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 good king henry

Pot on seedlings as they grow; not a perennial repot. Good King Henryis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Clump-forming herbaceous perennial with a deep taproot, arrow- to triangular-shaped dark green leaves on upright stalks, and slender greenish flower spikes; dies back in winter and re-emerges in spring..

What size pot to step good king henry up to

Pot good king henry 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 good king henry

Pot good king henry 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 good king henry

Pot on before it is root-bound. Check good king henry 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 rich, moisture-retentive 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 good king henry 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 good king henry

Good King Henry wants rich, moisture-retentive loam. Deep, fertile, humus-rich, well-drained soil, pH 6.0-7.5. Dig in plenty of compost or rotted manure before planting, as this perennial stays put and feeds heavily over years. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting good king henry — frequently asked questions

How often should you repot good king henry?

Pot on seedlings as they grow; not a perennial repot for good king henry. Good King Henry is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into rich, moisture-retentive 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 good king henry need?

When is the best time of year to repot good king henry?

Can you put good king henry straight into a much bigger pot?

No. Even a fast-growing good king henry 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 good king henry after repotting?

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