How to Divide Agapanthus Without Losing Years of Flowers

Understand the cost before you pick up the spade

Agapanthus divides easily and the pieces almost always survive. That is not the question. The question is what you give up. A clump that has spent five years building the congested root mass that makes it flower heavily is set back to the beginning by division, and the resulting pieces commonly take two to three years to flower again. If your plant is flowering well, dividing it is a decision to have fewer flowers for several years in exchange for more plants.

There are three good reasons to divide. The clump has become genuinely old, with a hollow dead center and flowering that has declined over several consecutive seasons. You want more plants and are willing to wait. Or a container has physically split and the plant must come out anyway. Wanting the clump to look tidier is not a good reason, and neither is a pot that looks too full.

The interval between divisions should be measured in many years. Five to eight years for a ground clump, and often longer for a container plant that is still flowering, is normal practice. Anyone dividing agapanthus every two or three years is systematically preventing it from ever flowering properly.

When to do it

The best moment is early spring, just as new growth is beginning to show, because the divisions go straight into a season of active root growth and re-establish quickly. The alternative is immediately after flowering finishes, which also works but leaves the pieces less time to root before cold weather.

Do not divide in the depths of winter when the roots are inactive and cut surfaces sit wet in cold soil, and do not divide in high summer while the plant is carrying flower stems. A deciduous clump divided in winter, with no leaves to show you where the growing points are, is also far easier to butcher by accident.

Dividing a clump, step by step

The physical job is more strenuous than delicate. Agapanthus roots are thick, fleshy and interlocked, and a mature clump is heavy and stubborn. Force is acceptable; the plant tolerates rough handling far better than it tolerates being divided into pieces that are too small.

1. Lift or knock out the whole clump Drive a fork in well outside the leaf spread, working right around the clump before levering it up, so you cut as few of the thick roots as possible. For a container plant, run a long knife around the inside wall and tip the whole thing out onto its side.
2. Wash or shake enough soil off to see the crowns You need to see where individual growing points sit before you cut. A hose run over the root ball for a minute reveals the structure and makes it obvious where the clump will separate naturally, which saves you from slicing through the middle of a crown.
3. Cut into generous pieces, never small ones Use two forks back to back, an old knife or a pruning saw. Each division should carry at least four or five growing points and a substantial mass of roots. Pieces smaller than that survive but take an extra two years to reach flowering size, which defeats the point.
4. Discard the dead center On an old clump the middle is usually woody, hollow and lifeless. Throw it away. Keep only the vigorous outer sections where the roots are pale, firm and plump, because those are the parts that will grow away strongly.
5. Let the cut surfaces dry briefly, then replant Leave the pieces in a shaded, airy spot for an hour or two so the cut surfaces dry off and are less likely to rot. Then replant at the same depth as before, crown level with the soil, in a container barely larger than the piece or in prepared ground.
6. Water once and then withhold Give each division one thorough watering to settle soil around the roots, then water sparingly until you see new leaf growth. Freshly cut fleshy roots in constantly wet soil are the one situation in which agapanthus rots easily.

Wear gloves throughout. Cut agapanthus roots release sap that irritates skin and is genuinely painful in the eyes, and every division exposes a lot of freshly cut tissue. Wash tools and hands when you finish, and do not leave discarded pieces where pets might chew them.

Offsets, the low cost alternative

If you want one or two extra plants without wrecking a good flowering clump, take offsets instead. In early spring, scrape the soil away from one side of the clump, find a fan of leaves at the outer edge with its own roots, and cut it away from the parent with a sharp knife pushed vertically down between the two. Draw the soil back over the parent and it will barely notice.

The offset itself is treated as a small division: potted into a container barely bigger than its roots, kept in sun, watered lightly until it is growing, and then left strictly alone. It will take the same two to three years to flower, but the parent clump keeps flowering throughout, which is the whole advantage of the method.

Seed, and why the results surprise people

Agapanthus sets seed freely if the spent heads are left on, and the black flat seeds germinate readily when sown fresh. Sow them just covered in a gritty free draining mix, keep them at around 60F (15C), and expect germination within a few weeks. Grow the seedlings on without disturbance and pot them individually once they have three or four leaves.

The catch is that seedlings do not reproduce the parent. Flower color, head size and hardiness all vary from seed, sometimes considerably, and it takes three to five years before you find out what you have. That is fine if you are curious and patient, and a poor plan if you wanted a copy of a plant you already like. For a true copy, divide.

Whichever route you take, write down the date, the parent plant, the number of pieces or seedlings and where each one went. Divisions and seedlings look identical for their first two years, and a label in the pot plus a line in your notes is the only way to know, two summers later, why one is flowering and another is not.