The main difference as far as I can gather between cordials and syrups is that cordial has a sour element whereas syrup does not. The sour element would add to the longevity of the liquid. I know of a few people who add a tablespoon of vodka to the cool syrup in order to increase its shelf-life
Some people use 1:1 sugar and water, for a rich syrup use 2:1 sugar and water. I am a bit sensitive to too sweet, so I opt for the lower sugar option, but then I have to make the decision to use the syrup quickly or to can it.
The process of making cordials and syrups using flowers is very simple.
Firstly, acquire about 200g (or 2 cups) of flowers, set them aside on a flat surface for a few minutes to loose their insect buddies.
While this is happening, boil a litre of water and add the water and 600g - 700g of sugar to a pot. Bring to a boil and then pour the hot sugar water over the flowers. Leave to steep for a few minutes.
For a cordial, you will want to add acid, be that from lemons, vitamin C powder or citric acid. It is likely that there will be a colour change when you add the acid.
Allow your flowers to steep covered over for a day, strain the liquid into sterilised bottles or ice cubes trays. If you are not going to be canning your bottles of syrup/cordial, keep it in the fridge.
Canning it for longterm storage
To can, line a large pot (stock pot) with tea towels, place the bottles into the pot so that the bottles are not touching. Add warm water to the pot to the level of the liquid in the bottles, do not go above the bottle lids.
Bring the water to 85 degrees C for 20minutes or 75 degrees C fot 30 minuttes. Remove when done and allow to cool. If canned properly, the syrup should last indefinitely as long as the bottle is left unopened.
Great flowers for making cordial from:
Gorse (March) Coconut flavour
Flowering Currant (April/May) Blackcurrant flavour
Lilac (May) Be sure to remove the flowers from their bitter stems) Floral
Elderflower (June) would benefit from the zest and juice of a lemon or two
Rosebay Willowherb (July) Tastes like cranberry juice drink
Meadowsweet (July) would benefit from the zest and juice of a lemon or two. Almondy/ medicinal flavour
Rose petals (Summer) Floral