In love with leaf amaranth
Leaf amaranth is a nutritious green well adapted to warm climates and has become one of our favorite greens both in the garden and in the kitchen. While in cooler months we may also grow kale, in hot times of the year this is our go to cooking green.
We like it so much that our son’s name came from calaloo - as both the plant and a dish made from it are known in the Caribbean. We first got to know amaranth in Mexico where its known as quelite - and is often grown within milpa (corn plus a diversity of other crops) agroecosystems. We later got to know it further in the Caribbean where its known as calaloo broadly or bhagi in Trinidad. Leaf amaranth is a significant part of diets in many parts of the world, including sub-Saharan Africa, Meso-america, and the Caribbean - where it provides essential nutrition as it has high levels of proteins and micronutrients such as iron, calcium, zinc, vitamin C and vitamin A. In many areas it is one of the principal vegetable crops, providing significant contributions to people's’ health with its rich minerals and vitamins.
While some may recognize leaf amaranth from bunches seen in Chinatown or other Asian markets, many people may have more experience or knowledge about amaranth as a grain - from which flour is sometimes made.
There are many species used as a leaf vegetable, some are weedy species that are collected, others are cultivated exclusively as a leafy vegetable, while some species are grown for both grain and greens. The main species of interest for their greens are all in the genus Amaranthus and include A.blitum, A. caudatus, A. cruentus, A. dubius, A. hypochondriacus, A. spinosus, A. thunbergii, A. tricolor, and A. viridis - the species in bold are those grown for seed as well - they typically have blond or light brown seeds, whereas wild and vegetable amaranths have black seeds. In subtropical and tropical areas of the world where at least during parts of the year growing more temperate adapted leafy greens (like kale, chard, spinach, etc) is difficult, leaf amaranth provides a delicious and nutritious part of diets. In Hawaii, it is already grown for Asian markets and it has a history here, yet its utilization could be more widespread. It is an essential plant for home gardeners and those trying to grow more of their own food, as it is so easy to grow and so productive, while also being delicious and very nutritious.
Many farmers and gardeners known A. spinosus known as spiny amaranth or pigweed - this is a plant that you definitely want to keep from setting seed in your garden or field! In many places in Hawaii this is a prevalent weed with high numbers of seed in the soil seed bank - one plant can produce more than 100,000 seeds! We have been trying for the last 5 years to see if its possible to fill the niche that spiny amaranth plays in fields with some of the edible (not spiny) species and to see even if some hybridization between the spiny amaranth and edible species occurs. While we have not eliminated spiny amaranth, we have well established populations now of a couple of edible species which come up spontaneously in our field, in some cases nudging out the spiny amaranth. Once the first couple true leaves are up, you can tell whether its a desirable species or the spiny weed - and weed accordingly.
If the edible species are in the way, you can easily hoe them or let them grow up to young harvestable stage and then pull whole plant to weed and harvest simultaneously. While you can grow leaf amaranths as a crop by direct seeding it or starting it in the nursery - our very best plantings come from spontaneous populations that come from plants left to go to seed in the field. The seed is tiny so don’t sow deeply!
Regardless of whether you purposely plant it or not a plant will be ready to harvest in 3-5 week, and typically in around 8 weeks (though varying among species and time of year) flowering and setting seed. It is thus a relatively fast cycle crop. More dense plantings will result in smaller plants while giving plants a foot apart will result in many species of plants up to 4-8’ tall if left untended.
There are two main ways of cultivation and harvest. One is to do dense plantings and then come in when plants are young and succulent and pull whole plant up by its roots - this is how the plant is often seen in Asian markets - a single harvest at 3-4 weeks after planting. We tend to have more widely spaced plantings and to let plant get 1-2’ tall (~4 weeks) and then harvest the younger leaves and stem - such pruning then causes the plant to bush out - and we subsequently harvest young leaves and stems from side shoots. If well maintained, a plant harvested in this way can give food for perhaps 4-6 weeks or beyond depending on weather and pest pressure.
In some cultures the leaves are blanched, then squeezed, then eaten as it, or stewed or sauteed. We tend to chop leaves finely and then stir fry at high heat with oil until some leaves start to get crispy. Very young leaves can be eat raw in salads, but in general its best to cook leaf amaranth as the leaves contain oxalic acid - an anti-nutrient also found in spinach and beets/chard that leaves a funny feeling on your teeth and metallic taste in your mouth. Heat breaks down some of the oxalate - though blanching and pouring water out is more effective. Eating too much oxalic acid can interfere with calcium absorption by the body. But cooked amaranth greens as part of a diverse diet should pose no problem.
Amaranth tolerates heat and drought well because it is what’s known as a C4 plant - that is it carries out photosynthesis in a different way than most plants do - via the C3 pathway. Corn and sugarcane are other examples of C4 plants. C4 plants evolved a number of times and are able to close their stomata (the small pores on the bottom of leaves which let gases and moisture in and out) when under water stress - thus preventing excessive water loss - but continue carrying out photosynthesis with CO2 they have stored in specialized cells. C3 plants on the other hand, cease photosynthesis (and thus growth) when they are water stressed and close their stomata. Amaranth and other C4 plants are ready for climate change!
Our favorite variety is the one presently for sale on the Hawaii Seed Growers Network as “Calaloo”. We were given the seeds by a friend in Florida who received them from a student from Surinam - we grew them in the Ethnoecology Garden at the University of Florida for multiple generations. During the past 6 years we have grown this variety - of the species Amaranthus dubius - consistently. We have let plants go to seed and are now able to harvest from spontaneous plantings almost all year round.
We love amaranth so much - we can’t help ourselves - and so have during the past years and months been collecting varieties and species. We have presently in the field in Waimanalo around 30 varieties of probably 5 species - from USDA collections, other seed companies, Taiwan, etc. We will save seed and grow larger quantities of those that do best, are beautifully unique, and/or taste delicious. Watch for some of them in the Hawaii Seed Growers Network store. Truth told, though, even though we are seeing lots of nice colors and fun diversity in terms of taste and growth habit - the Surinam-Florida-Hawaii Calaloo is still our favorite.
Our only major pest on leaf amaranth is leafhopper (Empoasca solana). During dry hot times leafhopper damage on both cultivated and weedy amaranths can get very high - you will see yellow streaking on leaves from where they have been feeding. The best approach is to harvest young plants/leaves and to wait for wetter weather, as controlling leafhoppers is quite difficult and part of the whole point of growing amaranth is that its low input! We have not had disease issues on our leaf amaranth. Occasionally there is some lepidoptera damage which could be controlled with Bt or Spinosad, but we have never found this to be necessary.
Further information about leaf amaranth is available her from the World Vegetable Center in Taiwan: http://188.8.131.52/web_crops/indigenous/cooperators%20guide_amaranth_s_web.pdf
I have a number of relevant publications about amaranth I am happy to share if interested. Email me at jbost[at]hawaii.edu