Mar, Apr, May, Sep, Oct, Nov
At its best:
Jun, Jul, Aug
Sow the patch with an appropriate seed mix, sprinkling half the grass seeds in one direction and the rest in the other. Lightly rake over the seed and protect it against birds with netting.
Alternatively, cut out the bare patch of lawn, rake the soil and add topsoil if needed then patch the gap with new pieces of turf.