A frequently asked question is: “Dear Jerry, I live in Brisbane, but I cannot seem to grow basil through our winter. What can I do?”
Reply: Basil is a varied genus of tropical aromatic herbs, naturally occurring from Africa to Asia. Your problem may stem from the fact that most people grow the ‘industry standard’ basil, Ocimum basilicum, the sweet or Genovese basil, a smooth, productive, large-leaved warmth-loving but short-lived species of basil best suited to our spring and summer.
Home gardeners mostly grow Ocimum basilicum, Genovese basil, because they are familiar with its taste and aroma. This basil is used almost exclusively in commercial pesto. It’s unsurprising we are familiar with its looks because this is also the primary basil raised and sold in commerce. It’s also the number one result you’ll get from a web-search for basil.
Genovese basil is very productive. I demonstrated that I could harvest over 10 kg of premium, pesto-grade leaves (no stems or roots included) from a single packet of seed a gardening magazine included as a free gift to its readers: that’s a return of 1 kg per square metre. I also saved 150g of seed. With a minimum of 500 basil seed per gramme, that’s enough seed for 750,000 plants, sufficient to supply a suburb. Great for summer, Genovese basil quickly deteriorates in the subtropical autumn and usually dies in winter.
A word about pesto
Pesto is the name applied to a pureed herb. So successful has commerce been in producing Genovese basil that many Western people now believe that pesto is exclusively made from this one kind of basil.
Traditionally, aromatic herbs of many kinds have been pureed to make herb pesto. Isn’t that a liberating thought for the home food grower? One of my more famous versions was nasturtium and swinecress pesto made with walnut and served on garlic mini-toast as an entree for 150 guests invited to a home grown, home made lunch for an Open Day in 2009.
Diversity in basil
There is a large variety of basil and since each has a distinctive flavour and aroma, suddenly you have options not just for the table, but also options to better match a cultivar to your climate and season.
I often trim off seed bearing heads of non-hybrid basil and scatter them around the garden where there are gaps in other plantings. Some hybrid basil produce viable seed which come true to type, such as lemon basil (illustrated).
Sterile hybrids are propagated by cuttings. Tip cuttings, 5-7cm long, taken from vigorous shoots of short-lived perennial basil strike faster and more reliably in summer. Use fresh propagating mix. I use equal parts of fine perlite, coir, and horticultural sand (all of which can be bought from a decent garden centre).
Seed saving is easy, cut off ripe seed heads, remove any flowers or leaves, and dry somewhere warm and sunny where there is good air flow. Gather fallen seed and store seed in an airtight, re-sealable, labelled jar in the fridge where it will remain fresh and viable for around three years. Otherwise use home saved basil seed within a year while it is still fresh.
You get the best germination rates by sowing basil seed in spring or summer. I love lemon basil, but in the subtropics this exquisite annual grows fast and has a short picking season.
You can buy seed on line from a diverse range of species and hybrids to grow at home.
It can be fun hunting down less commonly grown basils at specialist herb growers that sell by mail order. I have been a customer of Renaissance Herbs since 1994 and I first bought from them to stock up and help plant the Sydney Herb Garden.
You can either sow basil direct into a prepared seed bed or in pots or trays, but choose a sunny position. Cover the seed in containers using a very thin layer of vermiculite. In a seed bed, lightly rake the seed into the surface and water in. If you mulch, add the thinnest possible layer of chopped organic sugarcane so only 50% of the surface is covered from the sun.
Water regularly and decrease the amount and frequency of watering as seedlings establish. Only water in the morning even in summer, and water on alternate days during winter. Water at the roots because wet foliage is susceptible to disease. Thinning seedlings allows air movement between plants, otherwise they may be attacked by root rot fungi or bacterial leaf spotting disease. Use the thinnings as your first harvest. Removing fallen dead leaves from plantings helps reduce disease problems and, as always, practice crop rotation in a food garden.
My four favourite winter staple basils are:
1. Sacred basil (Ocimum tenuiflorum). Grows knee-high and flowers and self-seeds all year round. Seedlings that germinate in footpaths never mature, and when you step on them they release a delightful aroma. Makes a mild pesto which goes well with roast vegetables, like yam, sweetpotato and pumpkin.
2. Camphor basil (Ocimum kilimandscharicum) produces tall, wand-like growth and may grow above waist height. Needs clipping to keep it in shape and it can be used to make an informal hedge. White flowers all year round. It is a sterile hybrid that strikes readily from cuttings taken in summer. Makes a robust-flavoured pesto which goes well with grilled capsicum and eggplant.
3. Thai basil (aka húng quế, Ocimum basilicum var. thyrsiflora). A decorative, ever flowering variety with a hint of anise which makes a mildly spicy pesto. This is native to south east Asia and it self-seeds in my garden.
Thai basil is an essential ingredient in Vietnamese and Thai cookery, especially in sweet and sour sauce, in larb salad, stir fried elephant foot yam stems, king’s salad and pho.
Thai basil has many varieties and all are particularly valuable in stir fries as the volatile oils responsible for its distinctive aroma are more stable in hot cooking, like stir fries, than other basils.
4. African blue basil (Ocimum kilimandscharicum x O. ‘Dark Opal’). Last year I learned to love this basil sold at the Trevallen Lifestyle Centre near Ipswich. One tubestock plant arrived with one flower on it last autumn and it hasn’t stopped growing and flowering since.
I get a highly aromatic pesto from this hybrid, a few leaves add zest to salads, soups and curries. One single tubestock plant is now knee high and covers four square metres in flowers and foliage. Every day it is filled with bees and other beneficial insects. It is a sterile hybrid so it produces no seed. I must take cuttings to perpetuate it this spring.
This is the best basil so far for attracting the widest range of beneficial insects into my garden, including a variety of caterpillar-controlling solitary native wasp species.
In a sustainable garden you can’t really ask for much more from a herb. Now you have four basils to taste test and which are capable of growing through a subtropical winter in either pots on a balcony, or in the ground. Four basils which provide all year round interest, distinctive flavours and aromas, high productivity, and all of them attractive to pollinators and other beneficial insects that help to control pests.
Director, Seed savers’ Network Inc.
13th June 2020