So you want to grow Basil
Basil ~ Ocimum basilicum
Family: Lamiaceae
I have grown basil in every house since I left home. Pots on balconies, patches in suburban gardens, beds on the property. It has never not worked. Basil is one of those plants that rewards almost any attention you give it and forgives most of what you get wrong. It grows fast, produces abundantly through the warm months, and the gap between fresh homegrown basil and a bunch from the supermarket is significant enough that once you start growing it you stop buying it. The Mid North Coast is close to ideal conditions. Warm summers, plenty of sun, and basil growing right outside the kitchen door from October through to April.
Getting the timing right across Australian climates
On the Mid North Coast, basil goes in from October and keeps producing until the weather cools in April or May. The warm, humid summers suit it well. The one thing to manage is the humidity-related fungal pressure that comes with our climate, which basil is susceptible to in dense, poorly ventilated plantings.
Subtropics (NSW coast, SE Queensland):
October through April. Succession sow every four to six weeks to maintain a continuous supply. A single planting bolts and finishes faster than you want it to in the heat. Staggered sowings keep fresh growth coming through the whole season.
Temperate (Sydney, Melbourne, Adelaide):
Spring through summer. October to March. In Melbourne, wait until soil temperature is consistently above 15°C before sowing. Basil planted too early in cool soil sits still, sulks, and is more vulnerable to disease than a plant put in at the right temperature.
Tropics (Darwin, Cairns, Far North Queensland):
Year-round in the dry season and into the wet. Basil handles tropical conditions better than most herbs. Manage fungal disease through good airflow and spacing. In the wet season, container growing in a sheltered position helps avoid waterlogging.
Cool and alpine (Canberra, Tasmania, NSW highlands):
Short season. November to February. Start seedlings indoors four to six weeks before the last frost date and plant out once nights are reliably warm. Protect from late frosts. Even a brief cold snap below 10°C damages basil noticeably.
Sweet basil is the standard kitchen variety and the one to grow first. Genovese is the classic Italian type with large, fragrant leaves suited to pesto and fresh use. Thai basil has a different flavour profile, more anise and spice, and is worth growing alongside sweet basil if you cook Asian food regularly. Purple basil looks good and tastes similar to sweet basil but the colour fades in cooking. Lemon basil is worth trying in fish dishes and dressings.
Soil & Fertilising
Basil likes rich, well-drained soil with plenty of organic matter. Unlike Mediterranean herbs that prefer lean conditions, basil responds well to feeding and produces more prolifically in fertile soil. Work compost through the bed before planting and the plant will reward you for it.
pH between 6.0 and 7.0. Slightly acidic to neutral. Basil is not fussy within this range and grows well in most reasonable garden soils.
A liquid nitrogen feed every two to three weeks through the growing season keeps the leaves large and the plant producing. Fish emulsion or a balanced liquid fertiliser works well. Heavy feeding does not reduce flavour the way it does with Mediterranean herbs. Basil fed regularly tastes at least as good as basil left to struggle.
Basil grows very well in containers on the Mid North Coast. A large pot with good quality potting mix on a sunny bench close to the kitchen door is a practical setup. Container plants need watering more frequently than in-ground plants and benefit from a slow-release fertiliser at planting supplemented with regular liquid feeds.
Sun and shade
Full sun through spring and early summer. In the peak of a Mid North Coast summer, some afternoon shade is welcome and extends the productive life of each planting before it bolts. A position with morning sun and afternoon shade suits late-season plantings better than full exposure. Through the cooler months of the growing season, full sun all day is ideal.
Sowing & Planting
Seed or seedlings, both work
Basil germinates readily from seed in warm soil. Sow direct into the bed or into trays and transplant once seedlings have four to six true leaves. Seed sown into warm soil at 20°C or above germinates in five to seven days. Cold soil delays germination and the sitting seeds are vulnerable to fungal rot. Wait until conditions are right rather than planting too early.
Nursery seedlings are a practical starting point and give you a head start of several weeks. Handle the roots carefully when transplanting, as basil does not appreciate root disturbance. Water in well and keep out of direct afternoon sun for the first few days while it establishes.
Space plants 20 to 30cm apart. Adequate spacing is important for airflow, which reduces the fungal disease that humid conditions encourage on the Mid North Coast. Crowded basil stays wet longer after rain and is significantly more susceptible to downy mildew.
Succession sow every four to six weeks through the season. A single planting bolts within six to eight weeks in warm conditions and the quality drops quickly once flowering starts. Regular new plantings maintain a continuous supply of young, productive growth through the whole summer.
Water & Light
Consistent moisture but not waterlogged roots. Basil wilts dramatically when dry, which is alarming but usually recoverable with prompt watering. What it cannot recover from is sitting in wet soil for extended periods, which leads to root rot and collapse.
Water at the base of the plant rather than overhead. Wet leaves in humid conditions on the Mid North Coast is the primary cause of downy mildew, which spreads rapidly through a basil bed once established. Drip irrigation or careful hand watering at soil level is better than a sprinkler over the top of the plants.
Container plants dry out faster than in-ground plants and need more frequent checking. A large pot in full sun on a hot day can go from adequately moist to wilting in a few hours. Check daily through summer and water thoroughly when the top centimetre of soil is dry.
Mulch lightly between plants once established. Keep mulch clear of the stem bases. Good airflow at soil level reduces the humid microclimate that fungal disease needs.
Problems and troubleshooting
Pests
Cluster on new growth and flower stems. They reproduce quickly in warm conditions and a light infestation becomes a heavy one within days. A strong jet of water removes them from the plant without chemical intervention. Neem oil or insecticidal soap for anything more persistent. Check the undersides of leaves and the growing tips weekly through the season.
Target seedlings and young plants at soil level, particularly after rain. They can remove a small plant overnight or eat large holes through established leaves. Iron chelate-based baits are effective and safe around animals. Check beds in the evening through the first few weeks after planting and after rain.
Various caterpillar species feed on basil leaves, leaving ragged holes and frass. Check the undersides of leaves for eggs and small caterpillars. Dipel (Bacillus thuringiensis) is effective and safe for edible crops. Hand-pick larger caterpillars when found. Exclusion netting keeps moths from laying in the first place.
Tiny insects that rasp the surface of leaves, leaving silvery streaks and distorted growth. More common in hot, dry conditions. Spinosad-based sprays are effective. Keeping plants well watered reduces the stress that makes them more attractive to thrips. Check new growth closely as thrips tend to concentrate where leaves are still unfurling.
Diseases
The most significant disease problem for basil in humid climates and one that has become increasingly common across coastal NSW. Yellowing on the upper surface of leaves with a grey-purple fuzzy growth on the underside. It spreads rapidly in warm, humid conditions with poor airflow and can devastate a planting within days of first appearing. There is no recovery once it is established in a plant.
Prevention is the only effective strategy. Adequate spacing for airflow, watering at the base rather than overhead, avoiding dense plantings, and succession sowing so you always have young plants coming through. On the Mid North Coast, downy mildew-resistant varieties are worth seeking out. Amazel and Eleonora have demonstrated reasonable resistance and are available from specialist seed suppliers.
A soil-borne fungal disease causing sudden wilting and browning of stems, often on one side of the plant first. The stem shows brown discolouration internally when cut. There is no treatment. Remove affected plants and do not replant basil in the same spot for at least two seasons. Avoid overwatering and improve drainage. Source seedlings from reputable suppliers, as the disease can be seed-borne.
Basil planted in waterlogged or poorly drained soil collapses quickly from root rot. It wilts despite what looks like adequate soil moisture, because the roots can no longer function. Free drainage and avoiding overwatering prevent it. In containers, make sure the pot drains freely and do not leave it sitting in a saucer of water.
Non-pest problems
Basil bolts, sends up flower stems, and the leaf production slows and the flavour weakens as the plant puts its energy into seed. It is not a failure, it is just the plant’s lifecycle. Pinch out flower stems as soon as they appear to delay the process and extend productive leaf growth by several weeks. Eventually the plant will bolt regardless and the quality drops enough that it is time to pull it and rely on the next succession planting.
Basil turns black and collapses at temperatures below about 10°C. Even a cool night can cause blackening of the foliage that looks terminal. On the Mid North Coast this is most relevant at the end of the season in April and May when overnight temperatures start to drop. Harvest generously before cold nights are forecast rather than leaving plants in the ground hoping for another week. Cold-damaged basil is not recoverable.
Basil grown in too much shade, picked too infrequently, or harvested after the plant has flowered extensively produces noticeably less flavour than young growth from a well-managed plant. Pick regularly, pinch out flowers promptly, keep the plant in good sun, and harvest in the morning when oil content is highest. Old leaves on a bolted plant are worth composting rather than using in the kitchen.
When and how to harvest
Harvest basil regularly from the moment the plant has enough growth to spare, which is usually four to six weeks after planting out. The more you pick, the more the plant produces. Regular harvesting encourages branching, keeps the plant bushy and productive, and delays bolting.
Always cut just above a pair of leaves, not from the tip alone. Cutting above a leaf node causes the stem to branch into two new shoots from that point. Over several harvests this turns a single-stemmed plant into a dense, multi-branched bush producing significantly more than one that is simply picked from the tips.
Never strip more than a third of the plant at once. Harvest in the morning after the dew has dried for the best flavour. The oils are most concentrated before the heat of the day drives them off.
Pinch out flower stems as soon as they appear. Once the plant flowers the leaf quality drops and bolting accelerates. Removing the flower stems as they emerge keeps the plant in productive leaf growth for several additional weeks.
Companion plants
- Tomatoes (the classic pairing, and genuinely beneficial)
- Capsicum and eggplant
- Asparagus
- Oregano
- Marigolds (Tagetes)
Plants that aren’t friends
- Sage (inhibits basil growth when planted close)
- Thyme and rosemary (different water requirements create a management conflict)
- Fennel
In the kitchen
Basil is one of the herbs that changes a kitchen. Having it fresh and abundant through the warm months shifts how you cook. You reach for it constantly, add it to things you wouldn’t have otherwise, and the food is better for it. The gap between fresh basil picked minutes ago and the stuff in a supermarket bag that has been refrigerated for a week is not subtle. One smells like summer. The other smells like the idea of it.
Basil does not keep well in the fridge. Cold temperatures turn the leaves black within a day or two. Store fresh stems in a glass of water at room temperature, like cut flowers, away from direct sun. They keep for four to five days this way. For longer storage, blanch leaves briefly in boiling water, refresh in ice water, dry thoroughly, and freeze flat. Frozen basil is not suitable for fresh use but works well in cooked applications.
Basil oil
Blanch a large handful of leaves briefly, refresh in ice water, drain and dry thoroughly, then blend with good olive oil until smooth. Strain through a fine sieve or cheesecloth. The result is a vivid green oil with an intense basil flavour. Keeps in the fridge for up to two weeks. Drizzle over pizza, pasta, soup, or anything that benefits from a basil hit without a leaf in sight.
Pesto
Basil, good olive oil, parmesan, pine nuts or walnuts, garlic, salt. Blend or pound to a rough paste. The ratio is flexible and personal. Homegrown basil makes a noticeably better pesto than anything from a jar. Freeze in small portions, an ice cube tray works well, and use through the cooler months when the plant is no longer producing. A productive basil season should fill a freezer drawer with pesto.
Basil salt
Blend fresh basil leaves with coarse salt and spread on a tray to dry. The colour fades to olive green but the flavour holds. Keep in a jar. Goes on tomatoes, grilled fish, and eggs.
With tomatoes
The combination that needs no justification. A ripe tomato from the garden, torn basil leaves, good olive oil, salt. That is a complete dish. It is also one of the strongest arguments for growing both plants, because the version made with homegrown ingredients and eaten immediately is genuinely better than anything assembled from shop-bought components.
On pizza
Added after baking, not before. Fresh basil leaves placed on a hot pizza straight from the oven wilt slightly from the residual heat and release their fragrance into everything around them. Putting basil in the oven kills the flavour. This is worth knowing and then making habitual.
In a simple pasta
Pasta, good olive oil, garlic cooked gently in the oil, a generous amount of torn basil added off the heat, parmesan. Twenty minutes start to finish. The basil should go in at the very end, after the heat is off, to preserve the fragrance. A dish that benefits more from good ingredients than from technique.
Thai basil in stir fries
If you grow Thai basil alongside sweet basil, use it in high-heat stir fries where the anise and spice notes work with the other flavours. Thai basil holds up to heat better than sweet basil and releases its flavour rather than losing it. A handful through a chicken or pork stir fry in the last thirty seconds of cooking is one of the more satisfying uses of something grown outside the kitchen door.
