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Herbs grow well in most types of garden soil and in most conditions. You can increase their numbers by dividing plants or taking cuttings. Want to know how to grow herbs in Australia? Seed can be sown direct into the ground. Or you can sow it in pots and grow the new plants in windowsill propagation units or a greenhouse.

Sowing

Sow seed of hardy annuals direct into the soil in spring either in a seedbed or in their growing sites. Half-hardy herbs can also be sown in their growing sites once all danger of frost is past. Sow the seed in rows and barely cover it with soil. Then water it well and thin out when seedlings are well established.

Sowing indoors produces plants ready for planting out as soon as the soil warms up and the seedlings have been hardened off in spring Almost fill seed trays or cellular modules with soil. Firm down the surface and water or stand the trays in water. Leave trays to drain before sowing fine seed into the compost surface.

Space out large seeds and sieve a thin covering of compost over them. Put the trays in a heated propagator, with an even temperature of 15°C. Once the seeds have germinated and are large enough to handle, transplant them to small individual pots. Harden off by leaving them outside during the day. Then return them to a greenhouse (or equivalent) at night, until they are acclimatised to outdoor conditions.

Planting

Before buying a herb that is ready to plant out in the garden or to grow indoors, check that it has no obvious disease or pest problems; avoid plants that are root-bound or have damaged stems. You may want to learn how to grow herbs in Australia, and buying is at the very start of this process. Plant out your new herb as soon as possible, however not during the hottest part of the day.

Dig a hole large enough to take the rootball, and remove any weeds from the soil. Put the plant in the hole and backfill with soil. Then firm the surface of the soil and water the plant well. In dry conditions water the plant daily until it is well established.

Harvesting

Evergreen herbs such as bay, rosemary, sage and thyme can be harvested from outdoor and indoor herb collections all year round. As can herbs that you have forced into growth in winter, such as mint, tarragon and chives.

Annual herbs, including basil, perilla, rocket, dill, nasturtium and coriander, are at their best during spring and summer – late summer in the case of basil. Since herbaceous perennial herbs including fennel, lovage and comfrey die back in winter, their harvest period is during the spring and summer.

When each plant has produced good leafy growth, harvest it in an even way, to maintain a well-defined shape. For a handful of leaves to add to salads or cooked dishes, pick the herbs just before you want them, at any time of day.

Dividing

To promote the vigorous growth of herbs or to increase their numbers, divide the plants in early spring, when they are still dormant, or in autumn when the growing season is coming to an end. In autumn, before dividing, cut back all the spent flowering stems. Then use a fork to lever the clump out of the ground. When the dump is loosened, lift it out and place it on the surface of the soil.

The traditional way to divide large plants is to place two forks back to back in the centre of the clump and prise the two sections of the plant apart. Keep on doing this to each section until you have reduced the size of the original clump and produced several new sections ready for replanting. Herbs such as chives can be prised apart by hand.

Most perennials, such as marjoram, chives, echinacea, tarragon, sorrel, creeping thyme and lovage, grow to form large basal clumps. The growth at the centre becomes weak, and leaf production usually declines. When the clump is divided, any unhealthy-looking sections can be discarded. This allows the new plant or division to grow healthy new shoots from the rootstock around its edge

Taking cuttings

Another methods in how to grow herbs in Australia, is by using cuttings. By taking cuttings from individual plants you can produce many new plants for your herb garden. You can use a cutting to reproduce exactly the plant from which you have taken the cutting. To take a softwood cutting, start by looking for strong and healthy new shoots as soon as the herbs begin to grow in spring. Cut them away from the parent plant with a sharp knife and, if you are taking several cuttings, put them in a plastic bag to keep them moist and cool, and to prevent them from wilting.

Prepare several pots or trays with a good, well-drained cuttings compost. Make a clean cut on the stem of each cutting just below a leaf node, so that each is 10 cm (4 in) long. Cut the lower leaves off each cutting, however leave a few leaves on the stem. Make holes in the compost with a dibber, and put the cuttings in the holes up to the level of the remaining leaves.

Label each cutting with name and date, then put the pot of cuttings in a heated propagator or a mini-greenhouse made of a plastic bag. Check the cuttings daily; if you are using a plastic bag, take it off and turn it inside out every day. When roots start to appear on the underside of the pot – between a fortnight and four weeks – begin to apply a foliar feed. When the plants are large enough, pot them on into individual pots. Pinch out the growing tips of leafy shoots to encourage a bushy habit.

The method for taking hardwood cuttings is similar to that for taking softwood ones, however hardwood cuttings prefer a very well-drained compost and, since they are taken later in the year – in autumn, when the stems are hard and woody – they need to be overwintered in cold frames or greenhouses before they can be planted out the following autumn. The rooting time for hardwood cuttings is much longer than for softwood cuttings.

A straightforward way to propagate herbs is to take root cuttings from healthy-looking plants during spring or autumn. Among the herbs that can be increased by this method are lemon balm, mint, sweet woodruff, bergamot, comfrey and horseradish.

Pests and diseases

Unless they are grown in crowded situations without free circulation of air, or kept either too wet or too dry, herbs usually remain free of pests and diseases. It is preferable to use organic methods rather than proprietary insecticides or fungicides to deter pests from food plants such as herbs. Many organic gardeners use a proprietary organic soap to make a soapy liquid to use on whitefly or greenfly infestations.

Brown spots on mint and chive foliage are symptoms of a disease called mint or onion rust. Badly affected plants should be dug up and removed from the herb garden, so that other plants are not infected. You can also sterilise the soil around mint plants to prevent this disease from occurring: place a layer of straw around the affected plant and set the straw alight – however take care that the fire does not spread.

Seedlings of basil and other herbs are prone to damping off and dying in the early stages of growth. Deterrents include good air circulation, hygienic conditions, judicious watering, and drenching the compost with a fungicidal compound before sowing. Scale insects may be a problem on the evergreen leaves of bay grown in containers indoors. Use a soapy liquid to wipe the leaves, and dislodge the scale insects with the head of a cotton bud.

Vine weevil, whitefly and red spider mites may be persistent in protected environments. However can be controlled using soapy sprays or biological controls. Eelworms or nematodes are used for vine weevil. That’s a parasitic wasp called Encarsia formosa for whitefly, and Phytoseiulus persimilis for red spider mites.