Water garden calendar, September

September is a time for clearing off decaying vegetation. Some of the marginals that have flowered can be cut back to one third at the beginning of the month, which will prevent some of the reedy plants from seeding everywhere and some of the flowering species may be encouraged to flower again.

Cut marginal plants back to one third to ensure reedy plants dont seed everywhere and to encourage flowering plants to do a bit more flowering.

Koi keepers want to be feeding fish with good quality food to build them up for the winter. You can collect offcuts from the plants if you want to propagate them. Just pull them off or cut them neatly as they emerge from a basket. If they have developed root hairs then they will be guaranteed to establish in any good heavy loam set in a well-drained pot sitting in about 2inches, 5cm of water. It may be time to replace tired and overgrown plants in the marginal baskets next month, so these will be a useful replacement.

Check the growth of some of the more vigorous plants is not getting too far out from home base. Some of these shoots can be cut off to make new plants.

Lilies should be the main attraction now along with the Fringe lily, Nymphoides peltata. A few bog plants like the Ligularias, the Lobelias and Astilbes may be putting on a show. This is when the robust foliage plants like the Hostas, Rodgersias, Rheums, Peltiphyllum and Petasites come into their own.

Lobelia and lilies help sustain the colour later in the season.