You may find that mature bulbs begin to flower less freely than in previous years - this is usually due to overcrowding. However, unless the bulbs are visible near the soil surface, as with Guernsey lily (Nerine bowdenii), this may not always be obvious to see.

Thinning Method

1. Use a garden fork to lift the whole clump as the leaves die down, taking good care not to damage them. However, when dealing with bulbs that prefer to be lifted in leaf (or 'in the green'), lift them just after they finish flowering.
2. Divide the clump of bulbs by hand, separating first into smaller clumps and then into individual bulbs.
3. Discard any unhealthy bulb, and remove any dead or diseased material from around the remaining bulbs.
4. Clean the good bulbs, removing the loose tunics, so that they are ready for replanting in freshly prepared soil.
5. Replant the bulbs as they were originally, in soil or in grass, positioning them in irregular groups. See planting in soil or grass for more details.