Lesson 1 - Naming, classifying and categorizing food plants
A plant can have many names. Perhaps the most widely used is the common name – the name given to a plant that’s in common usage. However, the common name of a plant changes depending on where you are in the world. A ‘courgette’, used in Britain and Ireland, is the same as the ‘zucchini’, used in Australia and North America; while a ‘winter squash’ in North America is what we in Australia call a pumpkin. And yet the term ‘squash’ is used to describe a whole group of plants as well. Confused yet? Well, it can be because common names are not universal, there can be many different common names for the same plant. That’s why we have scientific names for plants as well.
Scientific plant names, or botanical names as they are called, are based on a formal, scientific system for naming plants called botanical nomenclature. Each plant species has a latinised name with two parts – the first being the genus name, the larger group to which the species belongs, followed by the species epithet name. Botanical names avoid confusion and fit within a broader system for classifying plants, allowing for easy and clear communication. When writing a species name, we capitalise the first letter of the genus, but leave the rest in lower case, and italicise the entire name to denote its difference. The species epithet sometimes describes a notable feature of the plant. For beetroot, Beta vulgaris, the term ‘vulgaris’ refers to common or ordinary. While in Solanum tuberosum, the potato, ‘tuberosum’ refers to tubers, that grow under the ground.
The other name that many plants have is the cultivar name. It is derived from shortening the term ‘cultivated variety’ and is preferred over ‘variety’. Most cultivars have been bred and selected for useful or desirable characteristics, such as size, colour, disease resistance, vigour, etc. Most of the food plants we grow are cultivars – some being cultivars of species, others are cultivars developed from hybrids (crossing of two species together). When we write cultivar names, we place them after the species name and enclose them in single quotes with the first letter of each word capitalised. Some of the potato cultivars that Diggers sell include Solanum tuberosum ‘Sebago’, ‘Purple Congo’, ‘Red Pontiac’ and ‘Russian Banana’.
Diggers tip
The best way to remember what a cultivar name is, just think of the combination or cultivated and variety. The cultivar indicates that the plant has been bred for a specfic characteristic that is often included in the cultivar name.
There are different ways of categorising food plants. One way is to group them based on their plant family – close plant relatives that share similar characteristics, mostly through flowers and fruiting traits. Thus, we have plants in the family Solanaceae – tomato, eggplant, capsicum, chilles, etc.; or in the Brassicaceae family – cauliflower, cabbage, kale, broccoli, etc. A more common way to group food plants, particularly vegetables, is based on the part of the plant we use and eat. In this grouping we have root and bulb vegetables, such as carrots, potatoes, onions, leeks, etc., leafy greens like lettuce, spinach, mizuna, stem vegetables, including celery and asparagus, flowers, like broccoli and cauliflower, fruiting vegetables such as pumpkins, capsicums and tomatoes, and finally seed-bearing vegetables such as peas, beans and sweet corn.
Another way to group vegetables is based on their growing season – warm or cool. Warm-season vegetables are those that require warmer temperatures to thrive and grow successfully. In cooler climates these are planted in late spring and grow over summer into autumn, when air and soil temperatures are sufficiently high enough to support their growth (typically > 21°C). In warmer and tropical regions these vegetables can be grown successfully all year round. Examples include cucumbers, capsicums, chillies, corn, eggplant and tomatoes. Cool-season vegetables require cooler temperatures to thrive, generally between 10° to 21°C. They can be planted from autumn to spring, although some are sensitive to very cold temperatures (<0°C), particularly newly germinating plants, and should be established either before or after frosts. Examples include spinach, lettuce, radishes, kale, broccoli and cauliflower. Many vegetables can be grown successfully in both cooler and warmer seasons, with different cultivars more suited to specific temperature ranges. It can be difficult to grow cool-season vegetables in warm or tropical environments. However, there are vegetable cultivars bred specifically for their heat tolerance for use in these climates. Some gardeners also use techniques like shade to cool growing areas, as well as providing good drainage and air movement to grow crops that may not be ideally suited to a tropical climate.
Herbs are a diverse group of plants and are not to be confused with the botanical term ‘herb’ which refers to plants with only herbaceous tissue, a non-woody plant. Herbs are plants that have specific uses in one of three ways – in flavouring and cookery (culinary herbs), for their therapeutic and healing properties (medicinal herbs) or their fragrant properties (aromatic properties). A ‘herb’ is derived from plant leaves and stems, distinguishing them from a ‘spice’ which comes from seeds, bark or roots.
Many herbs are annual plants, completing their entire lifecycle in a season or year, Basil and Dill are good examples. A small number are biennial, growing foliage in the first year and then flowering and seeding in the second year – Parsley being a good example. Then there are perennial herbs, herbaceous plants that grow for many years, such as Mint. And some can even be woody plants (shrubs and trees), like rosemary and lavender.