Mar, Apr, May, Sep, Oct, Nov
In a sunny spot, dig a hole 45-60cm deep and lay pond liner or thick polythene in the base. Make drainage holes, then pour in a 3-5cm layer of grit or gravel.
Fill the hole using the excavated soil mixed with well-rotted garden compost or soil conditioner. Trim the top of the liner so it's hidden just below the soil.
Plant nectar-rich moisture-lovers, such as water flag irises, marsh marigolds and purple loosestrife. Water well while they establish and add a thick layer of mulch.