Without a spade, you can't dig, and if you can't dig you can grow ... before sharpening it. This is the best way to get an idea of how much sharpening your spade actually needs, since mud, dirt ...

The best time to dig is from October through December ... Dig out trenches to a spade's depth, known as a 'spit', and about 30cm (12in) wide. Place the soil from the first trench on the ground ...