Repotting guide

When & how to repot African Blue Basil (Ocimum kilimandscharicum × basilicum 'Dark Opal')

Also called Perennial Basil.

More about african blue basil

About African Blue Basil

Ocimum kilimandscharicum × basilicum 'Dark Opal' · also called Perennial Basil · herb

African Blue basil is a sterile interspecific hybrid that is unusually long-lived and vigorous, with camphor-scented purple-veined leaves and near-constant lavender flower spikes that are magnets for bees. Because it sets no seed it never truly bolts, so it stays productive for months. Tender to frost, it is often overwintered indoors as a perennial.

Mature size: 60-120 cm tall and 60-90 cm wide in a long warm season

Watch for — Frost kill: Has no cold hardiness and dies at frost. Take cuttings or pot it up and bring indoors before the first frost to keep the perennial going.

How to tell african blue basil needs repotting

Repotting on a calendar is less reliable than reading the plant. For african blue basil, 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 african blue basil 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 african blue basil

Pot on seedlings as they grow; not a perennial repot. African Blue Basilis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Large, shrubby, vigorous perennial-in-warmth that flowers almost continuously. Being sterile it never sets seed, so it keeps producing leaves; benefits from periodic hard pinching to stay bushy..

What size pot to step african blue basil up to

Pot african blue basil 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 african blue basil

Pot african blue basil 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 african blue basil

Pot on before it is root-bound. Check african blue basil 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 fertile, well-draining loam or potting mix 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 african blue basil 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 african blue basil

African Blue Basil wants fertile, well-draining loam or potting mix. Rich, moisture-retentive but free-draining soil at pH 6.0-7.5. Amend with compost; in containers use peat-free mix with perlite and a deep pot to support its size. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting african blue basil — frequently asked questions

How often should you repot african blue basil?

Pot on seedlings as they grow; not a perennial repot for african blue basil. African Blue Basil is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into fertile, well-draining loam or potting mix 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 african blue basil need?

When is the best time of year to repot african blue basil?

Can you put african blue basil straight into a much bigger pot?

No. Even a fast-growing african blue basil 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 african blue basil after repotting?

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