By Clive Larkman
Over the last few years I have written about as many herbs and edible plants as I can find. Many of these are part of the Columbian Exchange. This was a major shift in the food and culture of the entire world. It involved the movement of many unusual plants, animals, drugs and diseases between the old and new worlds. The Old World was the Eurasian complex and the New World was the group of countries from lower Central America and northern South America.
Without going into detail, the exchange had a major shift on peoples’ diets worldwide, with many people feeling that their diet consists of plants that have been grown in their region for time immemorial. The reality is a large percentage of the modern diet in developed countries consists of plants that were part of the exchange. The most profound being the capsicum group (chillies and bell peppers) where the fruits are so intrinsic to the diet and culture of many countries, that they are just accepted as having been there forever, e.g. the spice paprika in Hungarian cuisine and the chillies used in Indian curries. Both these plants came to these countries in the Colombian Exchange.
Two other plants that moved around the world are tomatoes and potatoes (sweet and traditional). Both of these have become the staple diet of many nations across the northern hemisphere. Traditional potatoes and sweet potatoes both came from northern South America and have many linkages in nomenclature but not in the genetics. They are connected at a high level as they are both in the order Solanales (the classification above Family) with sweet potatoes being in the Family Convolvulaceae and potatoes in the Family Solanaceae.
Plants in the Convolvulaceae are referred to as bindweeds or morning glory. Sweet potato is in the genus Ipomoea – the morning glory group. It also includes several garden species and many cultivars. There are two edible species Ipomoea batatas and Ipomoea aquatica. The latter is an Asian vegetable called Kangkong which is available in many non-Asian grocers around the country. Ipomoea batatas is the sweet potato. It also has the common names kumara and yam. The latter is a misnomer as yam is the common name for plants in the genus Dioscorea.
Like any plant that has been around for over one thousand years, there are a multitude of common names in a range of languages, especially the indigenous tribes of Central and South America. The name Batata is one of these and has been used as the species name. It comes in a range of colours, skin and flesh and is nearly always propagated by fresh soft tissue. It strikes easily, grows quickly and likes warm moist climates. It is frost sensitive and does not respond well to extended dry periods. Flowering is rare and will only occur in areas with tropical day lengths.
The edible tuberous root is long and tapered, with a smooth skin and firm flesh. Skin colours range from yellow to orange, through red and brown to purple with the flesh colours ranging from beige through white, yellow, orange, red and pink to violet and purple. The tubers come in all combinations. There is consistency in the levels of sweetness and the flesh colour with the paler forms being less sweet. The most common variety in Australia is the orange skin with orange flesh and is thought to be the US cultivar ‘Beauregard’. Although most of the ‘New World’ foods moved around the world via the Columbian Exchange, there is a lot of compelling evidence that some of the orange-fleshed varieties moved across the Pacific, through the South Pacific Islands and eventually with the Maori to New Zealand.
The plants prefer a temperature range of 20 to 35oC and performs as a perennial if the temperature stays in this range. In cooler climates it is an annual and needs to be planted in early spring to mid-summer to get enough warm growing weather for the tubers to form. They take between two and seven months depending on variety. They form not on the original root of the cutting but where the nodes touch the ground and form new roots. In warmer climates the tubers can be left in the ground until needed. In cooler climates they need to be harvested when the first frosts appear. They will store for prolonged periods if kept cool, dry and in the dark.
They prefer a pH of around 5-7 in an open soil that can be quite low in nutrients. However, if the soil is good for producing really blue hydrangeas, i.e. more strongly acidic, then the young plants will not survive. They are very sensitive to elevated levels of aluminium and respond well to extra applications of calcium.
As a food crop, they have become the staple diet in many parts of the world as far apart as China, the USA and Africa. They are high in energy and are healthier than the conventional potato although they are 75% water. Within the starchy flesh there are high levels of Vitamin A, C and B, along with good levels of potassium. Good food for active people but too high in calories for those trying to lose weight.
All varieties are excellent baked and served with lashings of butter and cinnamon or maple syrup. They make great chips, balance well with sweet chilli sauce and in many regions are turned into savoury deserts. In many parts of Asia they are used to make gluten free noodles. The young leaves and twirling vine tips are edible and work well in a green salad. There are a few varieties that have stunning gold, black or lime green foliage and are widely used as ornamental plants in hanging baskets and as weed suppressants in larger, warm climate gardens. Overall, the colours of the foliage, skin and flesh, along with their ease of growth, make these a must-have plant for all frost-free, temperate to tropical gardens.
Main photo: Modern kitchen gourmet potatoes (Image: Totum Revolutum, Pixabay)