Barley (Hordeum vulgare)
The Danish name for this plant, byg, originally means "the cultivated grain". Six-rowed naked barley and normal barley were established in Denmark as far back as the Stone Age. In the Viking Age, six-rowed naked barley became the most important type. Barley gave meal for bread, grits for porridge, and malt (sprouted barley) for brewing beer.
Rye (Secale cereale)
Rye started to make an appearance in Denmark in the late Bronze Age. The cereal probably came from the south with seed corn, and spread as a weed in the cornfields, before becoming accepted as bread grain. During the Iron Age, both climate and agriculture changed - and in the Viking Age, rye became the predominant type of grain. It is much more resistant to the winter cold, damp and drought than other types, and can be grown on sand or on less fertile soil. As well as being grown in Denmark, rye was also imported from abroad.
Oats (Avena sativa)
Oats were first seen as a weed (wild oats) but were cultivated in Denmark from the late Bronze Age. In the Viking Age, their use declined visibly, but nonetheless, oats are still used to feed both humans and horses and oxen.
Club wheat (Triticum compagtum)
Club wheat, also called 'bread wheat', is the only one of the previous strains of wheat that was still around in the Viking Age, perhaps because wheat generally prefers a dryer and warmer climate, like that of the Bronze and Iron Ages. Incidentally, the word wheat is derived from the word 'white', referring to the white flour.
Millet (Panicum miliaceum)
Millet was grown most in the late Bronze Age and early Iron Age. Because it requires a warm climate, it became harder to get a reasonable yield in the Viking Age, as the climate became cooler. So a lot of millet was imported from southern lands. A few grains of millet grown in Denmark in the Viking Age have been found, but it never became an important type of grain.
Linseed (Linum usitatissimum)
It was cultivated for food in the early Iron Age (500 BC), when people ate the oily seeds in bread and gruel. The seeds could also be pressed to get linseed oil, and used for oil painting.
Linseed was first introduced as flax in about 400 AD - most likely from Eastern Europe. The fibres from the flax stalks were used for textile production, and it became an important plant in the Viking Age. The word usitatissimum means 'the very useful', referring to the many different uses of flax.
Horsebeans (Vicia faba)
Horse beans were an important source of food in the old days. Beans contain a lot of protein, and as they can be dried and kept for years, they were very useful for providing a Viking family with food throughout the long, dark and barren Nordic winter. Originally the word 'bean' referred solely to the horse bean plant, but after the haricot bean (the green bean) was introduced in the 16th century, the plant lost its importance and was given the somewhat disparaging name of horse bean.
Peas (Pisum arvense)
Peas are full of protein and were a good supplement to a diet poor in meat. The fresh green peas that we have today only arrived in Denmark in the seventeenth century; but it is possible that they grew field peas in the days of the Vikings. Peas would be grown until they were completely ripe, and then dried. From Sweden we know of iron-age bread made of pea-flour, and the Vikings would certainly also have eaten 'gule aerter' - a soup made of pork and dried peas, seasoned with thyme.
The cabbage patch
Kálgardr ('cabbage courtyard') is the Old Norse word for a kitchen garden surrounded by a hedge, and the word is still used in some parts of Jutland. In ancient Norwegian law, there were penalties for going into other people's gardens and stealing cabbage, angelica or onions. If anyone took so much that its value could be reckoned in terms of money, he was to be considered a thief, and it was permissible to punish him on the spot.
Cabbage (Brassica) is a general term encompassing all the types of vegetable that come from wild cabbage. Rape, black mustard and turnip are some of the strains of brassica, that were around in Viking times. The old sorts of cabbage were very different from the types we know today, but a plant such as curly kale is probably the closest equivalent. Amongst other places, traces of cabbage have been found in the Fyrkat Viking castle.
Onion (Allium) and onion gardens are mentioned in Laxdoelas saga, among other sources. We don't know what type of onion the Vikings grew, but it could quite easily have been both normal onions and shallots. Besides this, they could have gathered wild onions. Garlic was also familiar to the ancient Scandinavians, but it was probably imported.
Angelica (Archangelica officinalis) was already being sold in markets in the days of King Olav Tryggveson, around 1000 AD. The plant grows best in damp areas, and besides being cultivated in hedged gardens, wild angelica would have been harvested. Both roots and leaves are full of Vitamin-C, so they were an important supplement to people's diet. The leaves were used as vegetables, and the roots as herbs or medicine.