Wash and dry your jars, lids and utensils ready to steralize.
Zest and juice the lemon. Finely chop the lemon zest. Finely chop the ginger. Slice the top off the feijoas, peel and dice them.
Put your water on to boil to sterilize your lids. Make sure your oven racks are in the correct position, then preheat your oven to to 160°C to sterilize your jars.
Add the diced feijoa to a very large pot with ½ cup of water. Bring to the boil, then boil on about medium heat for about 25 mins, stirring frequently. Cook until the fruit is soft and starts to break down. Put a saucer in the freezer.
When the fruit has been cooking for about 15 mins put your lids into the boiling water and your jars in the oven to sterilize. Dip the utensils in boiling water for a few minutes to sterilize them. The jars and the lids need to be heated for ten to fifteen minutes to fully sterilize.
Add the sugar, lemon juice and zest and chopped ginger. If the fruit is still in large pieces at this point you can remove it from the heat and use a masher to help break down the fruit.
Increase the heat and bring the jam to a boil. Boil vigorously for about 5 minutes, stirring frequently. Take the jam off the heat.
To test that the jam is done put a small spoonful onto the frozen plate. Allow the jam to cool, then use your finger to gently push the jam. If it starts to wrinkle as you push at the edge of the jam, your jam is done.
If not, return to the boil and boil for another two the five minutes, then re-test. Remember to put your plate back into the freezer.
Ladel pipping hot jam into hot, sterilized jars and screw on sterilized lids. Allow to cool completely, then label with the contents and date.