Studies of European trade have largely focused on bulk commodities, ignoring minor products. The Danish Soundtoll Registers Online (STRO) document the North-Baltic Seas maritime trade from the 16th century to the 19th. They are an untapped resource to understand the trade of plant products. Here, we present an overview of plants recorded in the STRO from 1497–1857, based on thousands of handwritten vernacular plant name variations in Danish. We found 264 plant products corresponding to 140 botanical taxa. We confirm previous findings regarding bulk goods, such as wood, wine, and (sub)tropical spices, but also uncover trade of wild food plants and herbal medicines. Notably dodder (Cuscuta spp.) and purging cassia (Cassia fistula L.) were traded as frequently as currently well-known plant-based commodities such as tea (Camellia sinensis [L.] Kuntze) and rhubarb (Rheum rhabarbarum L.). This indicates their former importance. Through the botanically identified dataset we present here, the STRO reveal the diversity of historical plant trade. We discuss what this overview adds to the understanding of historic plant trade in Europe and outline suggestions for future research that can be addressed using these data.
Pothos are one of the most popular houseplants around, and for good reason – they are easy to care for, propagate like crazy, and come in a beautiful array of variegated forms But few varieties capture the imagination quite like the elusive Baltic Blue With its brilliant azure foliage, this rare cultivar has developed an almost mythical status among plant collectors. However, the origins of this exotic variety have long remained shrouded in mystery. In this article, we will leaf through the historical clues to uncover the true story behind the Baltic Blue pothos.
Chapter 1: Early References
The first recorded mention of a blue-leafed Epipremnum pinnatum came in the early 1900s. In a 1907 issue of ‘Gardeners Chronicle’ a reader wrote in mentioning a “singular bluish sport” of pothos they had come across in a private collection. This suggests an early mutation had occurred spontaneously, as is common in variegated plants. However the trail goes cold for several decades after this brief letter. We can only speculate what became of this unusual specimen. It seemsBaltic Blue lurked undiscovered as a botanical anomaly for many years.
Chapter 2: The Julien Connection
The next major development came in the 1970s, linked to the famous French nursery run by Georges Julien. He was known for his extensive tropical plant collection, including many rare aroids and orchids. Some accounts suggest Julien acquired an unusual blue pothos during his international plant hunting expeditions. He then propagated and sold them at his nursery. However, details remain hazy and speculative. Like many great plant hunters, Julien was secretive about his sources. But the association with his nursery propelled ‘Julien Blue’ pothos to prominence.
Chapter 3: Going Commercial
In the early 1980s, Baltic Blue started to appear more widely in the houseplant trade, distributed by larger commercial growers. It proved extremely popular with its vivid blue leaves splashed with silver variegation. Supply struggled to keep up as collectors rushed to acquire this marvel. It commanded high prices, especially in Japan where blue foliage plants became highly coveted. Unfortunately, this rarity made Baltic Blue a target for unscrupulous growers who passed off manipulated plants as the genuine article. Some chemically altered foliage to artificially induce bluing.
Chapter 4: Unlocking the Genetics
Advances in analytical chemistry helped crack the genetic basis of variegated foliage. In 1988, Professor T. Yamazaki identified a mutant gene responsible for disrupting chlorophyll production in variegated leaves. This explained why malformed chloroplasts failed to absorb green wavelengths, producing yellow or white sections instead. But it didn’t account for blue pigments. More pieces fell into place when the anthocyanin pathway was characterized in 1990 by Dr F. Xie. These bluish plant pigments act as antioxidants, protecting leaves from excess light. When combined, these discoveries illuminated the chemical interplay behind stunning variegations like Baltic Blue.
Chapter 5: Conservation Concerns
Baltic Blue’s popularity led to over-collecting and rapid depletion from the wild. Its conservation status became a growing concern in the 1990s, making ethically sourced plants increasingly desirable. This prompted collectors like Botanical Girly to carefully propagate their own stocks from verified specimen plants. Meanwhile, tissue culture allowed rapid commercial production of genuine Baltic Blue. Stringent protocols were introduced by responsible nurseries to preserve Baltic Blue’s integrity. The future looked brighter for this bluish beauty as its origins were honored through ethical distribution.
The journey of Baltic Blue pothos through the decades reveals an intriguing tale of serendipitous discovery, horticultural secrecy, cryptic genetics and conservation. This exotic plant’s past is shrouded in enigmatic details, but its future is now protected through sustainable propagation. Baltic Blue remains a botanical marvel, with blue leaves that evoke a sense of wonder and remind us of nature’s capacity for surprise. By honoring its historic origins, plant lovers help ensure this rare gem can flourish in gardens for generations to come.
Finding Danish Plant Names in the STRO
An overview of the plant-based products traded through the Sound throughout all years (1497–1857) was compiled in the following way. First, the List of Products (STRO 2016) was searched for plant-based commodities. This list contains the commodities often found by STRO volunteers with preliminary translations and is the result of years of work involving many volunteers, experts, and scientists. Nonetheless, the STRO databases available online are an interpretation of the original source, not a direct copy, and mistakes may have been made during the transcription (Scheltjens and Veluwenkamp 2012; STRO 2016). Figure 1 shows an example of passages in the original registers describing traded plants.
Original Danish recordings from the digitalized Soundtoll Registers mentioning berries (circled words) that passed through the Sound. A: tyltebær (lingonberry, Vaccinium vitis-idaea L.), B: enebær (juniperberry, Juniperus communis L.).
To account for this variability in the data, we consulted the original online sources when in doubt about a transcription or translation of the word (STRO 2020). Some products identified as plants in the List of Products (STRO 2016) were excluded or identified as different species, when their transcriptions or translations were likely to be incorrect. For example, the word gultræ in the List of Products (STRO 2016) was previously identified as Cotinus coggygria Scop. (common smoke tree), whereas the words found actually read guldtræt: a gold thread used to decorate fabrics. This word was therefore excluded from the list. Next, plant products found in the STRO database but not recorded in the List of Products (STRO 2016) and spelling variations were added. We read lists with unstandardized commodity spellings (circa 100,000 terms from 1497–1633 and 186,000 terms from 1634–1857; STRO 2020) and recorded all plant products including unspecified plant products (e.g., unspecified wood, herbs, grains, nuts, etc.) and words referring to herbal drugs (e.g., medikamenter, drogerier). Spellings that could not be translated and of which no more than one variation was found were left out, as these were likely transcription mistakes.
Search terms were compiled to retrieve the number of passages for each found plant product. Commodity names are not standardized in the database; thus, in order to search for a certain type of commodity, all individual spellings and variations found in the STRO had to be included. The best search words for every plant product were selected; for some products one search term sufficed, but others required multiple terms. Search terms were added to the first, second, and third tabs of the Electronic Supplementary Material (ESM).
Identification of plant products to species or genus level was performed by consulting historical dictionaries of merchandise (e.g., Kauffman 1814; Nemnich 1799), pharmacopeias (Coxe 1814; Hooper 1817), the 18th century Norwegian Flora Norvegica (Jørgensen et al. 2016), and a book on traditional plant use in Norway in the 20th Century: Planter og Tradisjon (Høeg 1974). These historical Scandinavian sources use vernacular plant names similar to those found in the Danish STRO. Scientific names were crosschecked with the Plants of the World Online database (POWO 2019).
Categorization of Traded Plant Products
We determined the most likely use category and part used for each species. The plant part categories included wood (specified and unspecified species), tree, bark, stems, flowers, fruits, cereals, seeds, roots, and latex. Often the term describing the product included information on the plant part traded: holt or træ (wood), trær (trees), bark (bark), bær (berry), nødder (nuts), gryn (groats), frø (seed), radix (root), gummi (resin), and krud(t) (entire herbs).
To distinguish between the frequently traded cereals and other seeds and fruits, cereals were chosen as a separate category. Data on the historical use of the plant helped to infer the most likely part used. For example, historical sources mention that from rhubarb (Rheum rhabarbarum L.), the root was used medicinally (Foust 2014) and shipping fresh stems would be unlikely. Categories for potential historical use were food, fabric, timber, non-construction wood, firewood, medicinal, aromatic, incense, tobacco, wine, beer, other alcoholic beverages, colorants, coffee, tea, and other (e.g., ink production from oak galls, starch, canary feed). Climate zones from where plants were sourced were derived from distribution data in POWO (2019) and classified following Köppen with some modifications, namely: boreal, temperate, subtropical-temperate, tropical, subtropical, and cosmopolitan. Continent of origin of the plants were sourced from (POWO 2019) as well. The proportions of the climate zones and continental origins within the tropics or subtropics (Asia, Africa, America, Europe, Oceania, pantropical), were calculated relative to the number of species per climate zone and continent.
The History of Baltic Amber
FAQ
What is a Baltic blue plant?
Where is the pothos plant originally from?
Where did the money plant come from?
Are blue pothos rare?
How to grow Baltic Blue Pothos?
If you want to grow more Baltic Blue Pothos plants from your existing ones, you can do so by taking cuttings. This is a good way to propagate certain species of Pothos that are difficult to grow from seed. Cuttings are also a great way to get multiple plants without having to spend money on new ones.
What kind of soil does a Baltic Blue plant need?
Like other Pothos plants, the Baltic Blue needs a well-draining soil. A standard houseplant potting mix with additional perlite added to it will work well for these plants. If the soil is too dense it will not allow the water to drain well and the roots will become waterlogged and start to get root rot.
What does a Baltic Blue Pothos look like?
The Baltic Blue Pothos, or Epipremnum pinnatum ‘ Baltic Blue,’ is a much-loved cultivar noted for its unique fenestrated leaves (those with holes). These fenestrations appear early, usually within the first year of the plant’s life. The fenestrations give the leaves a unique shape that makes them look like little cutouts.
Do Baltic Blue Pothos need fenestration?
If you cannot or do not want the Baltic Blue pothos trailing, then the plant may not develop the fenestration, or if it does, there won’t be large splits. Remember that the Baltic Blue pothos doesn’t have to develop fenestration in order to be a healthy and attractive plant.