5 Agapanthus Divisions Potted into Terracotta Long Toms with Added Grit

Why five, and why they came out of one pot

A clump lifted after eight years in the ground will give you far more than five workable pieces. The number is a choice about pot size, not about the plant. Five fans of foliage, each with a decent set of white fleshy roots and at least three growth points, is what fits comfortably across five 20cm Long Toms without cramming. Push it to eight or nine tiny scraps and you get slower flowering, sometimes two full seasons of nothing but leaf.

The crown itself was the deciduous type, one of the Headbourne Hybrids, which take root disturbance far better than the broad evergreen Agapanthus africanus. That distinction changes everything about timing. Deciduous kinds can be cut hard in autumn as they die back. The evergreens sulk if you divide them cold and wet, so those wait for spring. Get the two mixed up and you lose plants.

Cutting the crown is a two-handed job with an old bread knife or a sharpened spade. The roots are thick, almost like a thin parsnip, and they snap rather than tear. A few broken ends do no harm. What matters is that each piece keeps a section of the woody central crown, because that is where next year’s flower buds sit.

Grit ratio and what it actually fixes

Straight peat-free multipurpose slumps into a dense airless block by the second winter. Agapanthus roots rot in that. The fix is coarse horticultural grit, the 4mm to 6mm grade sold in 20kg bags, mixed at roughly one part grit to three parts compost by volume. That is a genuine third of grit once you account for how it settles.

The grit does two separate things. It holds open air channels so the fleshy roots get oxygen, and it adds weight low in the pot so a tall Long Tom planted with a heavy flower stem does not blow over in an exposed spot. Perlite gives you the drainage but none of the ballast, which is why grit wins outdoors even though perlite is lighter to carry.

A John Innes No 2 base instead of multipurpose is the other route. It already carries loam and sand, so you drop the added grit to about one part in five. The loam holds nutrients longer, which suits a plant staying in the same pot for three or four years. Multipurpose plus grit is cheaper and lighter but exhausts its feed by midsummer of year one, so you feed sooner.

Crocks over the drainage hole are a habit worth dropping. Trials at RHS Wisley years back showed a single large crock can dam water above it. A square of fine mesh or just a generous grit layer keeps the hole clear without the dam.

The Long Tom shape earns its keep

A Long Tom is taller than it is wide, the classic Victorian forcing pot. For agapanthus that vertical volume matches how the roots grow, plunging down before they spread. A 20cm Long Tom holds nearly the root run of a 26cm half-pot while taking up far less bench space, which matters when five of them line a step.

Terracotta breathes. Water and air pass through the clay wall, so the compost dries more evenly and never stays sodden against the pot side. That same porosity is the drawback in summer, when a terracotta pot in full sun can lose its moisture fast enough to check flowering. Agapanthus actually likes a slightly pot-bound dry spell before flowering, so the trade lands in its favour more often than not.

The frost question is real with clay. A pot fired at low temperature will flake and split when saturated compost freezes and expands inside it. Look for pots stamped frost-resistant or, better, frost-proof. Whichcote and other British makers guarantee theirs to specific temperatures. Cheap imports rarely do, and you find out in January when the pot sheds a curved shard onto the paving.

Watering five deep pots without standing over them

Hand-watering five Long Toms is fine until August, when a hot week means twice a day and one missed evening browns the flower stems. A basic drip line solves it. A 4mm micro-tube off a 13mm supply, one dripper per pot rated at 2 litres per hour, run for ten minutes twice a day on a Hozelock or Gardena battery timer, delivers roughly two-thirds of a litre per pot per cycle.

The catch with terracotta and drip is placement. Put the dripper hard against the clay wall and water wicks straight out through the porous side before it reaches the root ball. Sit the emitter two-thirds of the way in toward the centre, pinned with a small stake, and the water goes down where the roots are.

Deep pots also need a longer, less frequent soak than shallow ones. Short frequent bursts only wet the top third and the lower roots stay dry, which is the opposite of what a plunging root system wants. Ten minutes twice a day beats two minutes six times a day for the same total volume.

Overwintering the deciduous divisions

Headbourne types are hardy to around minus 10C in the ground, but a plant in a pot has its roots exposed on all sides to the air temperature, so it behaves like something a full hardiness zone tenderer. The root ball, not the top, is what you protect.

Move the five pots against a house wall, ideally east or south facing, and group them close so they shelter each other. Bubble wrap around the terracotta, or a slip-on fleece jacket, keeps the worst frost off the clay and off the roots inside. The foliage dies back anyway on deciduous kinds, so you can cut it to the base once it yellows and there is nothing up top left to protect.

The bigger winter killer is wet, not cold. A pot sitting in a saucer of rainwater freezes into a solid block and the roots rot before spring. Lift every pot onto feet or a couple of bricks so water runs clear out the bottom. Tip out any saucers. A terracotta pot standing free-draining through a cold snap comes through where the same pot in a puddle splits and the plant inside turns to mush.

Stop feeding by late August. Soft late growth pushed by an autumn feed is exactly the tissue that frost turns black.

One more thing on the crown

The woody central knuckle you divided from is the oldest part and the least vigorous. Discard the very centre if it looks corky and hollow. Keep the outer fans.

First flowers, and the wait

A freshly divided agapanthus often skips flowering the following summer and puts everything into rebuilding roots. That is normal and not a sign the division failed. By the second summer the fans thicken and the flower stems come. Whether the same is true if you had pushed for nine divisions instead of five is the open question, because the smaller the starting piece, the longer that root-building phase seems to run, and nobody has pinned down exactly how small is too small.