The defining features of plants in the legume family are a seed pod that splits down two sides, which is usually the harvestable part of the plant, and an amazing symbiotic relationship with Rhizobium bacteria in their roots. This relationship enables each plant to take nitrogen from the air and turn it into nitrate, which feeds the plant. Effectively, the plants are able to produce their own fertiliser from thin air!
All members of the legume family play a significant role in the ecology of wild-plant communities as pioneer species that can grow in all sorts of difficult environments, and this is most likely a factor in why they were adopted by early farmers as crop plants. Another application of their ‘pioneering’ ability is their use as green-manure crops. They are grown to the flowering stage and then ploughed back into the earth, where they break down and add extra nitrogen and other nutrients, as well as organic matter, to the soil – making this an extremely useful fertilising technique for large areas. The practical aspects of green-manure cropping are covered in the Fertilisers.
Examples There are many different types of edible beans, but the archetypal ones belong to the species Phaseolus vulgaris that originated in the Americas and was a staple of indigenous agriculture in the central region of the Americas. This species has numerous common names, including French bean, kidney bean, string bean and haricot, and features a huge range of varieties, which can either have a bushy or climbing growth habit. It is one of the easiest vegetables to grow; its large seeds can be direct sown into the soil, where they germinate quickly, and the plant grows and bears pods in a matter of weeks. Other important legumes include broad bean (Vicia faba), garden pea (Pisum sativum), peanut (Arachis hypogaea), mung bean (Vigna radiata), pigeon pea (Cajanus cajan), scarlet runner bean (Phaseolus coccineus) and soya bean (Glycine max). A couple of particularly fascinating examples of legume crops are the lentil and wattles.
Lentil (Lens culinaris) is one of the earliest plants domesticated by humans. Evidence of its consumption by humans goes back to Neolithic times in the western Asian region now encompassing Turkey, Iraq and Syria. There are many different varieties of this incredibly useful pulse, which have been selected over the thousands of years these plants have been in cultivation, and seed colours now range from yellow to orange, green and black.
Wattles (Acacia species) are very important Australian legumes. Edible seeds from many different species, such as golden wreath wattle (Acacia saligna) and golden wattle (Acacia pycnantha), formed a staple part of the diet of Aboriginal people. Mulga (Acacia aneura) is found throughout many parts of inland Australia, and the tree’s wood was used by Aboriginal people for a variety of purposes, such as firewood and to create tools. Dozens of other wattle species have been recorded in historical documents as also being utilised for a multitude of non-culinary purposes.
The characteristic flowers and pods of legumes are the key identifying features of this very important food family.
Also known as fava bean, broad bean produces pods that are up to 30 centimetres in length.
Cultivation requirements Legumes need near neutral to slightly alkaline soil, as many of them – such as beans and peas – are not well suited to acid soil. Most legumes are rather intolerant of waterlogging and soil salinity, so a well-drained, friable soil enriched with a base dressing of well-rotted manure or compost will give the crops a flying start. Climbers such as peas require staking or trellising.
Because of their ability to fix their own nitrogen, most legumes will grow better than other plant families in low-nitrogen conditions. However, it is important that they have a ready supply of the various other essential nutrients if crops are to reach their full potential. For nitrogen fixation by the root nodules to occur, it is essential that the right strain of Rhizobium bacteria is present. Usually the process happens thanks to natural bacterial populations in healthy garden soil; however, it is also possible to obtain cultured strains of the optimum type of Rhizobium and inoculate the seeds before they are sown. This is routinely done in large-scale agriculture and horticulture.
Pests and diseases Most legumes are propagated from seed, and it is important to ensure that your seed supply (whether purchased or self-collected) is free of systemic problems such as bean blight (caused by the bacterium Xanthomonas axonopodis) and mosaic viral disease – both of which can drastically reduce yields. Sap-sucking pests such as bean flower thrips, white flies and two-spotted mites can build up rapidly once the crop is underway, and it is vital that they are managed as soon as they start to appear so you can avoid major crop losses (for helpful strategies, see the Pest and Disease Management section.
Solanaceae – the nightshade family
Origins There are over 2500 species in the nightshade family, which have provided many of the world’s tastiest and most important vegetable crops as well as medicinal and spice plants. Most of the important food species come from the Americas, and in particular the Andes Mountains.
Characteristics This fascinating family includes herbaceous plants, climbers, shrubs and trees. Species from this family are often recognised by their (generally) small, tubular flowers with five petals and five stamens. Various species produce chemicals called alkaloids, which often give the foliage and/or flowers a pungent smell. These chemicals are not an essential part of plant metabolism, but appear to have evolved as a defence mechanism to make the plants unpalatable to grazing animals. Perhaps the most famous alkaloid is nicotine, which is obtained from tobacco (Nicotiana tabacum). Weeds from this family often have names that should be taken literally – such as deadly nightshade – as the alkaloids they produce are toxic and definitely should not be consumed.
Examples Members of the family, such as tomatoes (Solanum lycopersicum) and potatoes (Solanum tuberosum), have been bred and selected for thousands of years so that the edible parts have lost any toxic properties that their wild relatives might have had. The tubers of potatoes have become one of the world’s largest sources of carbohydrates, in the form of starch. Other members of this family include eggplant or aubergine (Solanum melongena), capsicum and chilli pepper (Capsicum annuum), tamarillo (Solanum betaceum), pepino (Solanum muricatum), wild gooseberry (Physalis angulata), Cape gooseberry or Inca berry (Physalis peruviana) and goji berry or wolfberry (Lycium barbarum and Lycium chinense).
Australia has over 100 species in this family, with the most interesting being the Solanum species, such as kutjera or desert raisin (Solanum centrale), the fruits of which Aboriginal people dried and ate. Various other species of Solanum have edible fruits when ripe, but due to the toxic nature of this family generally, most of these plants are not commonly grown as food plants and should be regarded with caution.
Cultivation requirements The wild members of the nightshade family tend to be colonisers of disturbed areas of soil, such as after a bushfire or when a tree falls over, or along roadside verges that have recently been bulldozed. They germinate easily from seed and grow rapidly to maturity, so they need a high level of nutrition and relatively well-drained soil. Many solanaceous plants prefer acid soil.
Eggplant fruits are a good example of the edible part of solanaceous crops, and their pretty purple colour contrasts well with the green foliage.
The five-petalled flowers of the nightshade family are very distinctive and a highly useful characteristic for identification.
The fruits of tomatoes come in various shapes and sizes. They can also be a variety of colours, from red and orange to green and purple.
Pests and diseases The lush nature of plant growth in this family tends to be very attractive to a wide variety of pests and disease-causing organisms. Caterpillars such as cutworm are a big problem when establishing the crop, while sap suckers such as aphids, thrips and white flies are very common pests throughout the life of the plants. Fungal, bacterial and viral diseases that affect the foliage, fruits and vascular (conducting) tissues are also very common at various stages of the plant’s life cycle and will sometimes cause utter devastation to crops. It i
s well worth researching varieties that are best suited to your growing environment, as they will hopefully suffer from fewer pest and disease issues.
Rosaceae – the rose family
Origins Many of the food plants in this family were developed from wild species in Eurasia and North America, and they have been in cultivation for many centuries. Various fruit trees are the product of either deliberate or chance hybridisation, so they have a rather complex parentage. The upshot of this is that there are many different cultivars available that require vastly different climatic conditions, so it is important to research the best cultivar for your local growing conditions.
Characteristics Interestingly, many of our favourite fruits come from the same family as roses. The flowers are a defining feature of the family, with five sepals, five petals and numerous spirally arranged stamens. These flowers contain the female parts that give rise to soft and fleshy fruits.
Examples Family members include apple and crabapple (Malus pumila), pear (Pyrus communis), medlar (Mespilus germanica), quince (Cydonia oblonga), cherry (Prunus avium), peach and nectarine (Prunus persica), plum (Prunus domestica), apricot (Prunus armeniaca), raspberry (Rubus idaeus), strawberry (Fragaria species), blackberry (Rubus fruticosus) and almond (Prunus dulcis). Rose hep or rose hip is the fruit of various rose (Rosa) species, and is often made into tea. A valuable Australian contribution to this family is the native raspberry, of which there are several useful species, such as Rubus parvifolius.
Cultivation requirements Climatic considerations are especially important when selecting the right cultivars for your operation. Many members of this family originate in cool climates, where the ‘chill factor’ is vital to the success of crops such as apples, cherries and pears (the ‘chill factor’ refers to the number of hours below 7°C that the plant experiences throughout the cold or winter season, and requirements can vary from 150 to 1400 hours). Pollination is an important consideration for good fruit set in all types, and access to pollinators such as bees is vital to success. Peaches, nectarines and apricots are largely self-fertile and can be grown in isolation, but other fruits – such as plums and cherries – require cross-pollination and therefore need a mixture of different varieties to be grown near to each other to provide pollen and to ensure good fruit set.
Pests and diseases Queensland fruit flies, red spider mites and pear and cherry slugs are all devastating pests that can cause major economic damage to fruit yields. In addition, bacterial and fungal problems such as Phytophthora root rot and fire blight strike the roots and foliage of many species, reducing the plant’s ability to take up nutrients and water.
The strawberry is an important edible member of the rose family that holds its seeds on the outside of its fleshy fruits.
Carrots are typical of many crops in Apiaceae, where the edible portion of the plant is a swollen tap root.
The stunning umbrella-shaped flower head of the carrot family is a characteristic common to all of its members.
Apiaceae – the carrot family
Origins This family contains over 3500 species that are found across most of the globe, with the majority of edible and useful species coming from Eurasia. Given the success of this family, it would seem that there are many other potentially useful species in countries such as Australia.
Characteristics The umbrella-like shape of its flower heads and seed heads distinguishes this family; an interesting bit of botanical trivia is that the family was once called Umbelliferae. The foliage is often divided into sections and usually contains essential oils that give off a pungent aroma, especially when crushed, which makes many species particularly useful as herbs. The seeds, roots, leaves and stems of various species are utilised as flavouring and food sources, while other species have medicinal properties.
Examples As well as some of the classic root vegetables, such as carrot (Daucus carota) and parsnip (Pastinaca sativa), there are also herbaceous vegetables such as celery and celeriac (Apium graveolens), and herbs such as dill (Anthemum graveolens), coriander (Coriandrum sativum), caraway (Carum carvi), fennel (Foeniculum vulgare) and curly parsley (Petroselinum crispum). An Australian contribution to this famous food family is a relative of celery known as sea parsley or sea celery (Apium prostratum), which is very easy to grow and has a very strong flavour.
Cultivation requirements The food crops from this family are mainly annuals and biennials that grow easily from seed, which, for many species, can be readily collected from the urban farm, provided the crop is disease free. Indeed, many of the herbs from this family, such as curly and Italian parsley, will often produce volunteer seedlings in vegetable plots where they are being grown. Most members of the family are fast-growing plants with short life cycles, and they respond extremely well to extra soil fertility in fairly neutral pH conditions. For the root crops in this family, it is vital to have friable topsoil to a depth of at least 500 millimetres; the various herbs will grow in a variety of soil types across a wide range of climatic conditions.
Pests and diseases Soil-borne fungal diseases and pathogenic nematodes tend to cause the most damage to this family, as many of its members – such as carrots and parsnips – are harvested for their edible roots. Root-knot nematodes, black root rot, Sclerotinia rot and bacterial soft rot can affect crops at any stage between sowing and harvest. Notes on dealing with these various problems can be found in the Pest and Disease Management section; however, crop rotation helps to avoid these problems and is a particularly important practice when growing this family.
As with other grains in the grass family, sweet corn (which is also often known as maize) is one of the world’s most important food crops.
Poaceae – the grass family
Origins Grasses are very cosmopolitan and are found across all but the coldest parts of the globe. Crops such as wheat and barley were first cultivated in the Middle East, rice originated in Southeast Asia, and indigenous peoples domesticated maize in the Americas. The aforementioned plants form a huge proportion of the world’s food and have proven to be the most economically important crops developed by humanity.
Characteristics Grasses all feature more or less linear leaves that have parallel venation, which distinguishes them from the majority of other edible plant families. The flowers are generally inconspicuous, so the plants are normally pollinated by the wind rather than by insects such as bees. The edible portion is usually the seeds; however, vegetative parts such as leaves and shoots are sometimes consumed (for example, with bamboos).
Examples As well as wheat (Triticum aestivum), rice (Oryza sativa) and maize (Zea mays), other grains such as barley (Hordeum vulgare), oats (Avena sativa), sorghum (Sorghum bicolor), millet (Panicum miliaceum) and rye (Secale cereale) are also widely used. Bamboos (Bambusa species) provide young shoot tips as a food throughout Asia, while sugar cane (Saccharum officinarum) is a source of sweetener across the globe. Given the ease of large-scale production, grain crops are not usually an important crop for urban farms. The grasses that are more likely to be found in the urban farm are maize (Zea mays) as the vegie sweet corn, or lemongrass (Cymbopogon citratus) as a culinary herb. Aboriginal people collected seeds from various native grasses, but these were apparently never grown as intensively cultivated crops. However, there is evidence that grasslands were ‘cultivated’ in a different sense, through the use of fire to spur growth. This growth provided seeds for harvesting and plants for grazing animals, such as kangaroos, which were then more easily hunted.
Cultivation requirements With the exception of rice, which is grown in paddies with copious volumes of water, most edible grasses are fairly adaptable to a variety of soil and climatic conditions. However, they require relatively high levels of fertility to reach their full cropping potential.
Pests and diseases Fungal diseases of foliage, crown and roots are the most common problems found in cereal crops. Corn crops are particularly susceptible to stem borers, which are the caterpillars (larvae) of several species of moths. Althoug
h cereal and other grass crops are generally not going to be a major part of the average urban farm crop mix, the general principles of controlling fungal diseases within them can be found in the Pest and Disease Management section.
Rutaceae – the citrus family
Origins Most of the edible plants in this family originated in Southeast Asia and Australia; however, they have been in cultivation for so long that many of the commonly grown citrus cultivars have arisen in cultivation, often as chance seedlings. For hundreds of years, citrus plants were grown in special greenhouses called orangeries to get them through harsh European winters.
Characteristics The feature that all members of this family have in common is that most parts of the plant contain essential oils that are usually very readily detected, particularly when the fruits or foliage are crushed. These oils produce the flavours and aromas that we have come to know and love from this family. Most of the useful members of this family are trees and shrubs that can be used to create habitat for wildlife such as birds, which can help to control insect pests. A good example of this is the rather thorny native Australian finger lime (Citrus australasica) that not only has delicious fruits, but will also provide nesting opportunities for small insect-feeding birds.
Examples Citrus trees are by far the most important members of this family, and include orange, grapefruit and tangelo (which are various forms of Citrus aurantium), lemon (Citrus limon), mandarin or tangerine (Citrus reticulata), cumquat (Citrus japonica), pomelo (Citrus maxima), citron (Citrus medica) and lime (both the exotic, Citrus x aurantiifolia, and native Australian types). The herb rue (Ruta graveolens) is also a readily grown member of this aromatic group.
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