Taking root cuttings of herbs such as Bay, Horseradish is an easy way to propagate new plants.
Layering branches of herbs such as Rosemary, Sage, Thyme is an easy way to propagate new plants. In the Spring, cover a low growing branch of the herb with soil, and weight down with a stone to keep the layered branch moist. By the Autumn, check carefully to see if the branch has grown roots. If it has rooted, cut off the new plant and plant it in the new location.
Storage. Best used fresh but will keep for a couple of days in a closed container, to help retain moisture, in a fridge. Many soft herbs such as parsley, oregano, sage, can be frozen. See here for method.
Many herbs come in named varieties with variations in colour, form, aroma and flavour.The choice is yours.
Edible flowers. The main use of edible flowers is to provide colour in a salad. You could use nasturtiums or chives for example.
Stevia (Stevia rebaudiana), is a calorie-free natural sweetener originally from Paraguay in South America, but now grown commercially in South America, China and Africa. The natural leaves contain up to seven sweet compounds (glycosides) and an array of antioxidants. The amount of sweet compounds in the leaves, is greatest just before flowering. The commercial product available in the shops, has been highly processed to extract the Reb A, and is packaged in the form of a white powder with other bulking agents to make it look like powdered sugar.
Stevia requires warm growing conditions such as can be found in a cool greenhouse in the UK, where it should grow up to 70 cm high and wide. They are tender plants and will not survive frosts. If you pot up a plant in late Winter, it will survive over Winter in a sunny windowsill, and start growing again in early Spring, when you can take cuttings.
To maximise production of leaves, you should pinch out the growing tips(which you can use as a sweetener, or root them in moist compost for more plants) when they are about 20 cm tall and again mid Summer to cause the plants to form more shoots. If not pinched out, they will just become lanky, produce small white flowers and no more leaves.
Sow Stevia seed in late Winter in a propagator or on a warm windowsill in moist compost. Germination can be slow and growth for the first month or two, is very slow.
Or grow Stevia plants from over-wintered cuttings rooted in a propagator.
Pot on in good potting compost and plant out in their final positions in a cool greenhouse or other sheltered position late April in full sun. Old tomato grow bags make a good place to plant up Stevia plants. Ensure that the plants have good drainage and good ventilation. Handle carefully as the stems can be brittle and easily break.
When planting outside where conditions are suitable, place the plants 45 cm apart in rows 60 cm apart.
Harvest the individual stems at midsummer and again when they stop growing in late Autumn. Gather them into bunches and hang them up to dry in warm, well ventilated place, as you would do other herbs.
Alternatively, dry slowly over a low source of heat until the leaves are crisp.
Strip the dried leaves from the stems and discard the stems.
Store the crisp dried leaves in an airtight container until you are ready to use them. You can use a food processor or coffee grinder to turn the dried leaves into powder.
Pests and diseases do not seem to be much of a problem where the plants are grown outside. Aphids and whitefly can cause problems in a poorly maintained greenhouse. Fungal disease should not be a problem provided the plants are kept well ventilated.
Preparation of the leaves for use. (Unchecked recommendations from other sources)
Fresh Stevia leaves extract. Crush 1/2 cup of fresh leaves and add to a heatproof container. Pour on 1 cup of boiling water and leave to infuse for 1 hour. Strain through a fine filter and store the strained liquid in a covered container in the fridge for up to 2 weeks. This should produce about 3/4 cup of Stevia extract, equivalent to the sweetness of 3 cups of sugar. Add small amounts of the liquid as a sweetener to taste. Try 1 tsp of Stevia extract = 1 Tbsp of sugar.
Dried Stevia leaves tea. Fill a tea infusing spoon with the crushed, dried Stevia leaves, and add to a heatproof container. Cover with 1 pint, or 500 ml of boiling water and allow to infuse for some 15 minutes. Remove the infusing spoon and store the liquid in a covered container in the fridge for up to 2 weeks. This should produce about 2 cups of Stevia tea, equivalent to the sweetness of 2 cups of sugar. Add small amounts of the liquid as a sweetener to taste. Try 1 tsp of Stevia tea = 1 tsp of sugar.
For longer storage, put the prepared tea or extract in to ice cube tray and freeze and store in the freezer.
Stevia preserved in alcohol. Take a covered container such as a jam jar and add 1/2 cup of crushed, dried Stevia leaves. Then add 3/4 cup of 40% spirit such as vodka, screw on lid and shake and leave in the fridge for several days. Strain and place in a clean jam jar and store in the fridge. Add small amounts of the liquid to taste.
Powdered Stevia can be used directly over food by sprinkling a small amount directly onto the food.