Maritime archaeological excavation and sampling

Archaeological investigation in and around the locus of the archaeobotanical remains discussed here took place over two excavation campaigns (Fig 2). In 2019, a trench measuring 2 x 6 x 1.5 m was excavated forward of the archaeobotanical sampling locus. No archaeobotanical investigation was conducted during that excavation. In 2021, a trench measuring 2 x 3 x 1.2 m was placed aft and inboard of the 2019 trench, separated from it by about 1.3 m. Diving archaeologists employed standard excavation tools and methods, including a venturi water dredge for removal of suspended sediments. After each excavation rotation, a mesh catchment bag attached to the water dredge discharge was recovered and sifted on the deck of the surface support platform. The material captured in the catchment bag from a locus in the western corner of the trench included almond shell and peppercorns. Subsequent excavation in that locus delivered more almonds and peppercorns, and revealed deposits of saffron directly underneath and adjacent to a deck beam, in a stratum 5–10 cm below the sediment surface. Archaeological divers collected the saffron deposits by hand, and observed several additional discrete concentrations of archaeobotanical remains in the trench balk. They collected sediment block samples from this locus for archaeobotanical analysis, placing them in plastic containers. The saffron was recovered in a water-filled plastic sample bag. These samples were stored initially at Blekinge Museum and later shifted to the Department of Archaeology and Ancient History, Lund University. At the conclusion of the excavation campaign, the trench balk at the spice locus was reinforced with casks staves that originated from a position directly adjacent to the spices, with the intention of continuing excavation and sample recovery in that locus in future interventions [6].

All necessary permits were obtained for the described study, which complied with all relevant regulations. The 2021 maritime excavation campaign was conducted under permit 431-1299-2021 (permit holder: Blekinge Museum; project archaeological director Brendan Foley) authorized by Länsstyrelsen i Blekinge, Sweden (Blekinge County Administrative Board). The collected and studied botanical specimens are curated at the Department of Archaeology and Ancient History, Lund University (address Helgonavägen 3, 223 63 Lund, Sweden, for contact: Dr. M Larsson).

Processing and laboratory methods

The botanical remains recovered from Gribshunden originate from four sediment block samples of 0.5–2.0 liter each. All samples were processed by floatation with running water, and sieved over three mesh sizes: 1 mm, 0.4 mm and 0.25 mm. The saffron stigma masses were collected by hand by divers, and the deposits were placed in a 5-liter bag during the dive. This was not subject to wet-sieving; the “water-sample” (sample 5, Table 1) contained the concentrations of only stigmas. Flotation was unnecessary, and would have posed a risk of damaging the delicate strands.

Morphological identification of seeds, fruits, nutshells, flower parts, and leaves was undertaken using a microscope (x8–80), with comparisons made to relevant literature [24–26] and to a modern reference collection of seeds at the Department of Archaeology and Ancient History, Lund University. Since recovery, all plant remains have been stored in containers with water. The plant remains were kept in water during microscopic examination.

After identification, all species were quantified from individual samples. In some cases (clove and almond), different botanical parts of a species were identified; these parts were counted as separate examples. Complete and incomplete specimens were also distinguished. The approximate quantity of saffron was obtained by pouring the water sample containing the stigmas into a measuring beaker, allowing time for the stigmas to settle to the bottom of the beaker, and reading the volume. Presence of saffron stigmas in the four sediment samples (present in the hundreds) is indicated with (√), as it is unclear if the stigmas were in situ or were deposited in the samples due to excavation activity during which some stigmas dispersed into the water and might have settled on the seabed within the excavated unit. Presence of small endosperm (seed) fragments from almond, leaf parts and undetermined specimens are indicated in Tables 1 and S1 by presence (√). All analyzed plant material are held at the Department of Archaeology and Ancient History, Lund University.

The exotic spices, and the total botanical assemblage

All recovered botanical remains were subfossil specimens. Identified economic plant species are presented in Table 1. The preservation state is noteworthy. Many plant remains feature fruit flesh and skin, still colored (Figs 3–9) and the saffron retains its distinctive aroma after 527 years submerged. Excluding the saffron stigmas which were quantified by volume (450 ml), a total of 3097 plant remains representing 40 species were identified from the sediment samples (full dataset S1 Table). They comprise 1 species of cereal, 1 species of oilseed, 4 species of fruits and vegetables, 8 species of spices, 2 species of nuts, 1 species of medicinal plant, and 23 species of wild taxa. The spices are numerically the most abundant plant remains in the assemblage, representing 86%, followed by nuts 12%. Crops, fruits, and vegetables make up a small portion of all the edible plants recovered thus far from the shipwreck. Wild taxa are represented by 2% in the plant assemblage, and these most likely entered the deposits over time as contamination from the coastal environment. In addition to the identified plant remains listed in S1 Table, sediment samples contained small plant debris from marine algae and remains of marine animals (shells, ligaments, perioctracum from mussels).

The archaeobotanical data discussed in this paper include only economic plant species typically used in food preparation or medicinal application. Wild taxa of the local flora fall outside the scope of this research, and therefore are excluded. Notes on some critical identifications of plants rarely found or previously unknown from archaeological deposits are discussed below.

Crocus sativus (Fig 3). The most important part of the saffron flower for human use is one of its female organs: the style, ending in three red-orange stigmas. Identification of saffron was based on the presence of these stigmas, also known as filaments, strands, or saffron threads. The recovered saffron stigmas do not consist of smaller pieces that have broken apart over time, or from handling by divers or during laboratory preparation and examination. Instead, the stigmas have a characteristic trumpet-like shape at the end of the pestle, indicating that the recovered strands are intact. Today and presumably historically, the price of saffron is determined by its quality. Grading criteria include the length of the threads. High-grade saffron is composed of whole or cut threads (stigma with or without part of the style), and premium quality eliminates the yellow/orange part of the style [27]. Typical length of modern saffron stigmas are ca 2.5–3.5 cm [28]. Measurement of 50 Gribshunden stigmas with removed styles produced an average length of 2.36 cm. Thus, the Gribshunden saffron threads are consistent with modern grading for premium quality.

Several discrete concentrations of red material were noticed in sample 3, ranging in size from ca. 1x1 cm to ca. 5x5 cm. These were observed in the sample prior to wet sieving, and were removed from the sediment in which they were embedded. Each of the concentrations was placed in water, which quickly turned red/orange. Examination under a light microscope showed the concentrations were finely ground saffron stigmas; the water was colored as the powder dispersed into it. It is unclear how the ground saffron was stored on the ship, as no container or bag enclosing the powdery substance was observed. We hypothesize that the saffron might have been in textile bags which have not survived.

Piper nigrum (Fig 4). Black pepper was identified by the whole unprocessed fruits, in which the outer skin (epicarp) was complete or near complete among most of the specimens. The outer skin of the fruit shows the characteristic pattern of wrinkles from the drying process of unripe fruit. Some fruits entirely lacked their outer skin, or retained only fragments of it. This condition exposed the characteristic radial vessels of the fruit, resembling that of white peppercorn. Peppercorns with partially preserved and shriveled skin were able to be identified as black pepper. The loss of the outer skin surrounding the fruit is likely due to degradation over time or from handling during excavation or wet sieving. Some immature specimens and stalk parts were also recovered, including a few small stalk segments bearing unripe berries.

Prunus dulcis (Fig 5). Almond was identified by the presence of its seed coat (testa). While the seed coats of some specimens were complete, most were incompletely preserved with seed coat halves or mere shreds. Small white seed bits from endosperm were attached to some seed coats. Fragments of the nutshell (endocarp) from almond were also found among the samples, characterized by pitted canals containing vascular bundles.

Syzgium aromaticum (Figs 6 and 7). Cloves consist of a lower quadrangular stalked portion (the hypanthium) that terminates in four thick spreading sepals, which surrounds a globular head (the crown) having four imbricated petals. Identification of clove was possible from complete unopened flower buds preserved, but also from different fragmented parts of clove that have broken up over time. These parts include the hypanthium, the globular head, detached membranous petals that would have been attached to the globular head, and fragmented ovaries and ovules which have been released from broken up ovaries situated in the upper part of the hypanthium. Clove stalk was also identified, as were numerous oil glands from the disintegrated hypanthium observed in the samples. Oil glands were not quantified, as these were present in the thousands.

Zingiber officinale (Fig 8). Ginger was represented by small parts of rhizome skin (epidermis) from the creeping underground stem. From rhizome skin parts, it was possible to identify the circular scars representing the nodes with small scales and buds, as well as small black dots on the surface of the skin. While most fragmentary skin was ca. 10–40 mm in length, a larger piece measured 60 mm. Adhering to some of the rhizome skins were whitish fibrous threads.

Cucumis sativus (Fig 9A). The seeds of cucumber can be difficult to distinguish from those of melon (Cucumis melo), as the size of the seeds are variable. Identification was possible by examining the fine anatomy of the seed surface: C. sativus has fine straight parallel lines in the middle of the seeds’ surface, and parallel lines which follow the oval shape of the seed. In comparison, C. melo have fine parallel lines of cells on the entire seed surface [29].

Economic plants from the Gribshunden shipwreck and archaeological comparanda

The economic plant species from the Gribshunden botanical assemblage represent a wide range of food plants, presented here in five food categories: cereals, oilseeds, fruits and vegetables, spices and nuts. We acknowledge the overlap between culinary and medicinal applications of these plants. Henbane is the only non-food plant identified in this assemblage. Henbane had medicinal and magical purposes, and is presented under a separate heading. The archaeological context can help determine the most likely use for the recovered plants. All botanical remains from the Gribshunden shipwreck were recovered from sediments within a one square meter unit located toward the stern of the ship. The locus that produced the botanical remains also held several wooden casks presumed to have contained foodstuffs and beverages [3,23] Among these plant species, all are edible except henbane, which was used only medicinally. Then, as now, some of these plants are commonly consumed as flavorings (saffron, black pepper, clove, ginger, black mustard, dill, caraway), others eaten as snacks or used in baking (nuts, berries, grapes, flax), and some could be eaten as part of a meal (cucumber). Grapes could have been consumed as raisins. Raisins and almonds could be consumed alone or as ingredients in prepared dishes.

It is unclear how these food plants were stored and transported. No containers of wood, metal, glass, or ceramic were excavated in the same locus. Similarly, this locus produced no remains of bags made from textile or leather, though it is possible that bags simply have not survived. Shells from nuts and ground saffron (conglomerates of ground stigmas) were recovered in the botanical assemblage, suggesting that these foods were handled and prepared close to the sample area shortly before the ship sank. From this, we propose that the economic plant remains were foremost intended as foodstuffs.

We speculate that the ground saffron was separated into several small packages. This possibly suggests medicinal doses or discrete volumes of flavorings for food or beverage servings; it could also indicate division based on ownership, or even packaging as gifts. However, detailed discussion of specific culinary use or healing properties of respective food plants during the Middle Ages is outside the scope of this paper. Medicinal preparation and application of these spices in medieval Europe was diverse, and information from Scandinavia is at best fragmentary. An overview of previous archaeobotanical data from the medieval Baltic Sea region with reference to selected food plants recovered from Gribshunden is summarized in Table 2. For each of the five food categories, we present the individual Gribshunden plant species with a summary of relevant published archaeobotanical documentation for medieval Scandinavia and the Baltic region. The archaeological record is, of course, incomplete. Cereal grains, oilseeds, nutshells, or aromatic fruit or seed condiments are sometimes represented in archaeological deposits. However, those plants used for their vegetative parts rarely survive archaeologically, unless preserved in the waterlogged contexts of latrines, wells, or underwater environments. Preservation of food plants in the macrofossil record may further be prevented if processed and used in other forms, such as ground or as powder, or pressed into oil. Written sources that mention rare food plants can, however, complement archaeobotanical data with insights into the procurement and consumption of these plants.

Elite consumers of plant foods recovered from Gribshunden

Knowledge about historical victualling and the diet of ships’ crews is primarily derived from written sources. Information on maritime foodstuffs is scant for 15^th century Scandinavia, and in the case of Gribshunden, no records detail the diet on board during its last voyage. For the years 1487 and 1493, however, documents provide some expenses for King Hans’ naval fleet [38]. The documents are scattered summaries kept by the king’s secretaries, usually recording supplies of arms and recruitment of soldiers. Notes from 1493 mention funds set aside for ships’ crew victuals. They consumed meat, butter, fish, bread, flour, salt, and vinegar. The accounts relate an ordinary and monotonous diet, similar to the fare of other sailors in medieval northern Europe. Provisions aboard three 16^th century Swedish naval ships (Lindormen 1546, Sankt Erik 1561, Vita Falken 1562) list the same foods, with the addition of peas [126]. Nowhere is there mention of spices, vegetables, fruit or berries for the common Jack Tars. Other accounts in Hans’ documents detail consumption of beer and bread, with higher-quality varieties differentiated according to rank and social status [38]. Higher-ranking individuals ate bread and biscuits made from wheat and washed it down with German beer. The working crew endured hard bread and lower quality local beer. Future excavations on Gribshunden may reveal even more stark differences in the food and drink of the nobility and the common soldier and sailor.

Baltic underwater archaeobotany offers additional victualing details from other medieval shipwrecks. Finds on the 15^th century Copper Wreck in the gulf of Gdansk included food remains of beans, plums, hazel, walnuts and onions [16]. The wreck also contained garlic, interpreted as medicinal [17]. These archaeobotanical data complement information in documents of the ship’s owner. These list expenses for victuals including meat, fish, salt, butter, fat, bread, flour, and beer [16]. Very few other medieval ships from the Baltic Sea have been archaeobotanically investigated. Two 13^th century wrecks are the Gedeby shipwreck, by the island of Falster, Denmark; and a cog vessel close to Oskarshamn, Sweden [127,128]. These were small vessels transporting livestock, grain, and iron. The wrecks produced only a few cereal food plants, interpreted as cargo remains.

Outside the Baltic region, a well-documented wreck from Northern Europe is the 16^th century carrack-type warship Mary Rose, flagship of Henry VIII [15]. Botanical remains from the wreck include peppercorn, hops, cereals, hazel, walnut, plum/greengage, cherry, and grapes. While nuts and fruit would have added variety to the diet, it is unclear if these were limited to officers, particularly as the fruits were mainly found in the ship’s hold and some in the galley supplies. The presence of peppercorns on Mary Rose is of particular interest for the study of Gribshunden. The recovery of peppercorn from multiple loci on Mary Rose suggests that some could have been for general use in the galley, while individual crew members also cached some for their personal use [129]. Among the contents of a barbers-surgeon’s chest were a few peppercorns, believed to have been part of medicinal supplies. Future excavations on Gribshunden may reveal similar multiplicity of use.

The plant material from Gribshunden contributes new knowledge about the foodstuffs consumed by the social elite in medieval Scandinavia. Considering that Gribshunden sank in the beginning of June, perishables such as ginger, grapes, berries, and cucumber were likely preserved as dried fruit, pickles, or jams to have been available for consumption all year around. It is unclear if ginger rhizomes were stored fresh or were preserved in some form. If fresh, the rhizomes must have been procured within days of Gribshunden’s departure from Copenhagen, as fresh ginger has a short shelf life. Other foodstuffs recovered from Gribshunden could be stored for far longer than fresh ginger. Spices from far distant origin, such as black pepper, saffron, and cloves would keep for long periods if they remained dry. Dill, black mustard, and caraway were likely sourced locally. Flaxseeds, almond, and hazelnut have long storage lives. It is probable that nuts were stored on board in their shells and cracked opened when ready for consumption, as broken shell parts were recovered from both nut species.

It is tempting to compare this wide variety of fresh produce to records of medieval maritime provisioning; but as the royal flagship, Gribshunden is a special case. Instead, the exotic foodstuffs from the king’s spice cabinet provide a window into the consumption patterns that likely followed in the elite landscapes of castles ashore. Despite the popularity of exotic spices among the medieval aristocracy, very few of these foods have survived archaeologically. The preservation of these plant foods on Gribshunden constitutes a discovery of great historical value. Spices and other exotic foods such as almonds were typically consumed only by society’s wealthiest. On Gribshunden these were not victuals for the working crew. Exotic food items are probably some of the most easily identifiable indicators of social context. King Hans was travelling on the ship together with his courtiers; these expensive exotic foods are linked to these passengers.

Danish archival sources from 1487 relate brief but telling details specific to King Hans’ expenses and activities aboard his flagship [38]. While laid up awaiting favorable winds in 1487 en route to Gotland and at a stop on Bornholm island on the return, Hans gambled on card games. In those few weeks, his recorded losses totaled 42 marks, nearly the annual salary of one of the ship’s senior officers. He ate candy and nuts, and with his companions, drank wine and particularly beer. On that voyage the ship reprovisioned with fresh barrels of local beer, as well as embstøll, a hopped Prussian beer originally brewed in Einbeck, Germany. Other recorded purchases for Hans’ sea voyages are consistent. He bought more confectionaries for the apothecary, nuts, and saffron while voyaging to Års, Jylland, Denmark. The amount of saffron purchased was prodigious: the cost was 36 mark danske, equivalent to nine months of salary for a senior officer on Gribshunden, or 18 months of salary for a sailor [38]. These documentary references combined with the remains of saffron, almonds, and hazelnut recovered from Gribshunden’s 1495 wrecking prove that the king regularly consumed these extravagant foods while at sea, and most probably while ashore.

In addition to information about the specific foodstuffs consumed, the written sources reveal circumstantial information about procedures and etiquette related to the king’s elite milieu at sea. The Gribshunden accounts of 1493 list royal court employees [38]. The “kelderswen” (källarsven), perhaps similar to an army quartermaster, managed the food stores. The “dugeswen”, perhaps similar to a chief steward, was responsible for laying out the royal tables for meals and banquets. No doubt similar roles and procedures were spelled out and followed when King Hans traveled on his flagship two years later.

The social context of luxury foods and spices

Food, both in its acquisition and consumption, provides insights to the economic and social aspects of a society. The archaeobotanical assemblage from Gribshunden shines a light on late medieval Nordic social structure. As King Hans traveled aboard his flagship on its final voyage, accompanied by a fleet of perhaps 18 other vessels, different social groups walked those decks. The king represented the pinnacle of the social hierarchy, the royal court and nobles represented the elite, the ship’s captain and senior officers another stratum, and the hired soldiers and ship’s crew the lowest social group in this floating castle. All of these individuals played important roles in the pageantry of the Kalmar political summit.

Saffron, black pepper, clove, ginger, almonds and grapes were exotic foods and spices out of reach for most people in medieval society due to cost and rarity. Only those who possessed sufficient financial resources could afford these expensive food items, a luxury limited to the elites. The elite certainly enjoyed consuming these foods, but their high cost and exotic nature also marked their social status [130].

The role of luxury foods and spices on Gribshunden may have served different purposes. The types of luxury foods found were primarily those of flavorings, and while at sea, these could have had been used for preparation of meals served to the King and his men, and other dried foods (grapes and nuts) could have been enjoyed as snacks. An interesting analog is a later royal document from 1627, which show that Gustav II Adolf (King of Sweden 1611–32) was well-stocked with spices and other exclusive foods on his naval trips [131]. Cucumbers, almonds, rice, figs, ginger, pepper, anise, nutmeg, saffron and alum were on his menu. Such historic documentation together with the botanical food remains from Gribshunden, suggest that consumption of luxury foods among royals was not limited to the main living quarters on land, but was part of the royal environment at all times, even at sea. Food is more than diet. It is inextricably linked to the expression of social and cultural identity. The consumption of luxurious foods was a crucial aspect of King Hans’ and other monarchs’ presentation of themselves to their subjects.

Had Gribshunden safely arrived in Kalmar, from its decks Hans would have employed all manner of elite signaling to impress the Swedish Council. The consumption of exotic foods certainly was symbolic of prestige and social superiority within Hans’ realm. It also demonstrated that King Hans and medieval Denmark were culturally integrated with the rest of Europe, and the world beyond the continental borders. The goal of the Kalmar negotiations was for Sweden to re-join the Nordic Union, consolidating the entire region under Hans’ rule. During the summer-long summit, Hans would have hosted banquets for the Swedish Council, possibly onboard Gribshunden but more likely on the grounds of Kalmar Castle and within the castle itself. Through hospitality and feasting, food is recognized in many cultures as a tool for the creation and maintenance of social relations. Feasting embodies two principal characteristics: first, a communal aspect of consumption in large groups, with food (and drinks) that are different from everyday practices; and second, a display of social prominence, with the presentation of food conveying economic success, high status, and cultural power [130]. Additionally, knowledge from and of foreign cultures is a way for the élites in stratified societies to manifest their status and secure political power [132]. All of the events that might have procceded in Kalmar were likely constructed not merely for practical purposes; they were political theater. The presentation of exclusive foods and decorative dishes would, in both organization and content, be designed as an integral part of the entertainment, and be a part of the display of the king’s status and power.

The banquets hosted by the elites featured feasting and lavish displays. These established and strengthened relationships, and were critical activities to bind political support and networks between states [133,134]. An example of this from the late medieval period is the great feast hosted by Henry VIII at Greenwich in 1527 to celebrate the conclusion of a treaty with France. From written accounts of the event, the courtly feast displayed a variety of luxurious foods and featured several exotic plant foods, such as clove, ginger, almond, mace, and cinnamon (but no saffron) [108]. If King Hans planned a banquet, the use of exotic foods and spices in elaborate cuisine would have showcased the symbolic power of the Danish crown. It would have been clear to all witnesses and participants that the Danish court followed the culinary trends of European courtly societies. It would have signaled the cosmopolitan identity of the king, his access to luxury commodities from far distant origins, and his royal court’s position in the global economy.

Along with hosting feasts, gift-giving played an integral part in the building and strengthening of relations in medieval culture [135]. Gifts of food and drink were common across medieval society. They could be contributions in kind to feasts or celebrations, or take the form of support and donations to individuals or institutions [136,137]. These gifts were as significant as the rank of the donor. In the upper echelon of northern European society, the range of gifted foodstuffs could be venison or other game, high-status birds, fresh fish, and wine [136]. Gifts played an important role in negotiations as well. The role of spices as prestige commodities during the Middle Ages was underlined by their use as gifts on political occasions [135]. For instance, spices prepared as gifts for ambassadors in the Baltic region are documented from Reval [46]. In 1494, the Reval Town Council sent an ambassador to Moscow. As gifts to dukes and a bishop, he presented foodstuffs including boxes of spices. On another occasion when traveling to meet nobles in Wenden and Narva in 1498, among the foods presented by the ambassador from Reval were pepper, saffron, ginger, and mustard. Gribshunden’s luxury foods similarly might have been intended as representation gifts on arrival in Kalmar. Similar to feasts, gifts made by the crown would express an opportunity to secure the peace by strengthening a personal relationship between the two rulers. Gifts, banquet ingredients, or at-sea consumables: given the context and the circumstances of the journey, all are possible purposes for the exotic foods recovered from Gribshunden.