The benefits of growing usable plants near your sleeping place—as opposed to having to search for them whenever you need them—are so obvious that people must have started the first gardens as soon as they discovered that plants would grow from seeds, and that seedlings could be transplanted. In the Germany of 1632 every household—from the grandest palace to the smallest hovel—would have some kind of fenced plot, garden, or backyard near the house for growing at least the all important kale. This article will try to take a look at these gardens, with special attention to the kind of garden a family settling in Magdeburg or Grantville would be expected to start.
Three styles of gardens were common in 1632: the formal renaissance garden, the medieval herbal garden, and the ordinary kailyard.
The main purpose of the formal garden was to display the power of the owner by showing how he could control nature. This style of garden with its regular rows of pots or standard trees, its knot gardens of topiary and clipped hedges, and its evenly spaced flowers and bushes wasn't limited to the grand manor houses, but would also be found on a smaller scale around the houses of anyone with social pretensions. If the area available for the garden was big enough, a secluded rose garden, to be visited only during the brief blooming season, was also a status symbol, as was an orangery where tender plants could be kept during the winter. The formal garden wasn't harvested in any way, so the household also needed to have a kitchen garden somewhere near, sometimes with the vegetables growing in orderly rows and patterns in the French potager-style, sometimes without any pretense to ornamentation and kept completely out of sight from the house and the formal walks. One of the most famous potager-style gardens is the Château de Villandry at: http://www.frenchgardening.com/visitez.html?pid=31106784011481.
The herbal gardens were made up of tiny plots of soil laid out in a pattern and separated by narrow paths. Each plot of soil would be planted with a single plant species—annual or perennial—and the plants would all be harvested—either as they were needed or when the entire crop was ready for drying and storage. This type of garden had its origin in the medical gardens at the medieval cloisters, but—at a time when most medicines were locally grown and made—an herbal garden was not something found only at the apothecary, but a type of garden planted by all major or isolated households and with at least one in each village.
The kailyard was originally simply a fenced-in piece of land, where the household grew its kale and any other vegetables and herbs it needed. The area absolutely had to be fenced securely to keep roaming pigs and other animals from eating the household's sole source of winter vitamins, and as this plot of land was so important to people's survival, it was regarded as a part of the house itself, and given the full protection of the law against thievery. By 1632 the simple kailyard was still a common part of the small households, and would remain so for centuries, but a household living above existence minimum would try for something a bit more elaborate.
The Average Garden
The gardening books of 1632 were usually written by gardeners working for royalty or nobility, but a look at the less grandiose schemes found in these books—combined with contemporary journals and diaries—suggests that an average garden in 1632 was likely to have borrowed elements from each of the three styles mentioned above. The main purpose of the garden would be to grow the vegetables needed for the household, but it would be laid out with the main paths in a formal pattern—usually a cross—and its content would include a large number of herbs each growing separately either within clipped box hedges in a kind of knot garden or used as edging and low hedges along the paths.
The contemporary books advised to find a free and open position for a new garden—sheltered from the north wind but with sun for most of the day—and suggested the area south of the house as the most likely place. There should be water either within the garden or nearby—but no chance of flooding in the spring—and the area should preferably be either completely level or gently sloping to aid drainage. If only a steep slope was available for the garden, it had to be terraced to prevent erosion, and sturdy steps should be build for easy access to all levels. If there were no buildings to shelter the garden from the north, one or more rows of trees should be planted there as soon as possible.
Once the position of the garden was decided, the area had to be cleaned of stones and roots, dug carefully, and leveled with the aid of a spirit level. A hedge of young thorny plants should then be planted around the garden in a trench filled with well-rotted manure, and with a brush-work fence on the outside to protect the hedge while it was growing. The books made it quite clear that this part of the garden could not be stinted: the fences had to be absolutely tight before any kind of planting could take place. And since pigs were allowed to run loose and find their own food in the towns as well as in the country, this really was necessary.
For the entrance to the garden one or more portals made of juniper columns—which would not rot in the ground—and willow branches—which were easily bent—was suggested, and a wooden gate should be hung on hinges to close the opening.
The next part of the project would be measuring out the pattern of paths. Most patterns started with a cross separating the area into four quarters, and if running water was available it was suggested that a narrow water channel be dug along one of the main paths and lined with handsome stones. Having water channels along both main paths and meeting in a fountain where they crossed was a scheme suggested only for the larger and more elaborate gardens, but a well as a central feature was practical and acceptable in even the most humble kitchen garden.
If a well already existed by the house, a central feature for the garden was still wanted. If the main paths were to be a formal walk lined with pots and ornamental plants, the central feature could be a pavilion or portal covered in climbing roses and vines, but even in what was to be entirely a working garden with all plants grown for food, it was still suggested that the center be marked with, for example, an urn or large clay pot planted with a small tree or large shrub. The basic for this layout was the biblical description of paradise, and was also used in the Muslim-style gardens still found in Spain.
Once the main paths were dug out and filled with white sand or pea-sized gravel, the secondary paths were measured out. Unless the garden was so small that the entire area could be reached from the main paths, there should be a path along the hedge—either right inside or some three feet within to create extra beds along the margin of the garden.
If further division of each of the four main quarters were needed for easy access, the obvious choice would be to split each quarter in four by secondary paths also laid out as crosses, but the gardening books provided a large number of drawings of various geometrical patters to choose from. To strengthen the pattern made by the paths, and shelter the new sprouts from the wind, it was the custom to line each bed in some way. Low fences of ox bones or painted brushwork were recommended for not interfering with the growth of the plants within the bed, but edging with clipped box, lavender, or herbs such as thyme, sage, and rue was also mentioned.
The Basic Vegetables
The preparations described above were most easily done in winter, but once a final layer of fine compost or old manure had been spread over the beds and worked into the soil, the garden was ready for planting in spring. Exactly what would be grown would of course vary from garden to garden, but some vegetables were grown by everybody with even the smallest piece of land.
The most important plant in the garden would be the winter-hardy kale, an originally wild European plant, and one of the oldest cultivated vegetables in the world. Kale was the only reliable source of fresh greens during the winter, and to be without it often meant scurvy for anyone not rich enough to own a forcing-house or at least buy sauerkraut. Kale doesn't keep long once harvested, and the leaves bruise and break easily during transport, so while it was grown everywhere, and sometimes filled most of a small garden, it was not planted in the fields or grown for more than local sale.
The most common way of serving kale was as a thick soup made by boiling the chopped leaves in the broth made from boiling salted pork, sometimes along with some chopped onions, and often with oats or barley added to further thicken the soup. In many households this dish would be served most days in the week with a bit of the pork, mustard and some rye-bread.
Swedes and Turnips
This group of vegetables was probably more popular in Germany than in any other country, and both Teltow in Brandenburg and Bortfeld in Braunschweig gave name to popular varieties. In these areas the big autumn and winter types were sometimes a field crop as well as a garden vegetable, but as with all winter vegetables they had to be either grown behind fences or harvested before the pigs and other animals were allowed to roam the fields in the autumn. Still, they stored very well, and many gardeners grew a few extra rows to sell, which made turnips the cheapest winter vegetable you could buy in most of Germany.
Winter turnips were often boiled to a puree or added to the kale stew, but could also be fried or even honey-glazed.
The fast-growing spring turnips, on the other hand, were ready for harvest early in the summer, and were very popular garden vegetables. They didn't keep well, and thus were not grown for export, but they were considered a delicacy and often served with roast or boiled duck.
The head cabbage had been bred by the Dutch and spread from Holland by their traders some decades before 1632, and it was thus a fairly new cultivar in the German gardens. It wasn't as hardy as the kale, but in a cool and airy place the harvested heads could keep for months, and when made into sauerkraut they could last all year without problems. Head cabbage was much easier to store and transport than kale, but sauerkraut was easier than either, and in some areas—one of them Magdeburg —head cabbage became a field crop, and an actual sauerkraut production took place for selling to ships and armies.
Sauerkraut was made by layering finely sliced white cabbage in barrels with salt and spices such horseradish and caraway seeds. After a while the cabbage juice brine would start fermenting, and once this process was finished, the product was ready for use.
Sauerkraut needed no further preparation before eating, but the un-fermented head cabbage was prepared in much the same way as the kale.
Kale, turnips and cabbage are all members of the same family of vegetables, and as the gardeners of the time were quite aware of the importance of crop rotation, it was the custom to use one quarter of the available vegetable beds for this family and change to a different quarter every year.
Next to the grains, rye and barley, it was the peas that were the most important source of nutrients. Not the fresh green garden peas (in Latin: Pisum sativus), but the hard and dry field peas (in Latin: P. arvense). Field peas were grown in several different varieties, all of which could keep for years once dried, and—as with the sauerkraut—some areas grew enough for an actually production for export.
Preparing a meal from dried peas took time: first they needed soaking at least overnight, and then the spoiled peas had to be picked out before they were boiled in water until tender. Once tender they would normally be mashed to a puree and strained through a colander to remove the tough pea-skins. The puree could then be mixed with the same salty meat broth as used for the kale, and boiled again with vegetable such as onions, leeks, carrots and parsnips plus herbs such as thyme or marjoram.
The succulent green garden peas, which are what most people today think of as peas, would be grown in cane-supported rows only in the gardens. They had to be eaten straight after being picked, and were a treasured summer delicacy to be gently steamed—to preserve the fresh color—and served either with a bit of butter or in a rich cream sauce. Mixing the peas with small, tender carrots, or steamed lettuce and pearl onions, are summer dishes that have remained popular from medieval times until today.
In 1632 the long green garden beans had barely arrived from America, and in many areas the European broad bean types were considered suitable for animal fodder only. In Italy, Sweden, the Low Countries and the UK broad beans were grown for the kitchen, but in Germany these would have been eaten only in the poorest households.
Peas and beans are from the same family, and as both have the added benefit of adding nitrogen to the soil, they were normally grown on a third or fourth of all fields as part of the crop-rotation. A similar rotation was recommended in the garden, and if filling a quarter of the vegetable beds with garden peas wasn't possible—and beans were not wanted even to feed the servants—it wasn't unusual to sow the rest of that quarter with field peas simply to improve the soil. These field peas could just be whatever kind was grown locally, but seeds of special types such as the large Grey Russian could also be acquired.
The Flavor Vegetables
A steady winter diet of rye bread, beer, yellow peas, and kale—plus salted pork and herrings—grew boring very, very quickly, and people tried to vary the dishes with small amounts of strongly flavored vegetables and herbs. So, if one quarter of the garden was filled with vegetables from the cabbage family and one from the bean family, then the third was likely to be filled with roots and members of the onion family.
Onions and Garlic
Regardless of the variety the taste of an onion depend on the climate in which it is grown, and a cold climate produce a much stronger flavor than a warm. Onions in Germany were therefore—like garlic—used more as a spice to flavor other dishes than as the independent vegetable it was considered in Southern Europe. Onions and garlic were commonly grown, but rarely as a commercial crop, and many made do with wild garlic gathered in the forests.
Leeks could—with a bit of protection—keep in the garden during a mild winter, but they needed more care and fertilizer than the hardy kale, and in most areas leeks were used mainly in soups and to vary the flavor of the kale and pea dishes.
Carrots and Other Roots
The common carrots in 1632 were not the orange-red roots, we known today, but rather dirty-white or pale yellow. The Dutch had developed quite a few varieties, all of which were used in soups and stews, for garnishing, and as side-dishes—very much like we use carrots today.
Yet another Dutch root, the parsnip, was popular in vegetable dishes all over central Europe in medieval times. By 1632, however, it was considered only fit for animal fodder in the south, where the Italian influence was strong, while in the west, where the connection to France was strong, it was used mainly in soups. Only in the northern areas did the parsnip maintain its popularity, and was served as separate vegetable dishes in the Dutch and English style.
The beetroot was grown in both a red and a white version, and despite it storing well during the winter, the most popular use in Germany was to pickle it in sour wine with caraway seeds and horseradish. The eastern European beetroot soups still popular today were known and mentioned in German cookery books, but it was not a common dish.
Other roots such as the radishes, the black and the white salsify, and the hamburger parsley (a type of parsley where it is the winter hardy roots that are used) were grown from time to time by those who liked them, but played no large role in the common kitchen.
The Manor Vegetables
In addition to the common vegetables the big kitchen gardens at the estates would grow quite a lot of the more delicate and rare vegetables, as well as the newest arrivals from America and Italy. The seeds for most of these rarities could, with a bit of effort, also be obtained by owners of more moderate gardens, and would be grown either in the fourth quarter of the garden or be tucked in among the plants in the other quarters. The big glass windows needed for an orangery or forcing house would be far beyond the means of most garden owners, but the construction of a few cold frames was perfectly possible for most. The contemporary gardening books describe very carefully how a flat hole should be dug within a frame of wooden boards, and filled with fresh horse manure covered with a layer of good soil and several woven grass mats in January. Come spring the soil in these frames would be much warmer than the surrounding ground, and tender vegetables such as the Mediterranean artichokes (often served elaborately garnished), cucumbers (mainly eaten pickled), fennel (mainly used as a spice), melons (a rare treat) and pumpkins (very rare) could get an early start—and a covering mat of woven grass in case of a late freeze.
Other vegetables not found in all gardens included the loose-leaf lettuce, which had been known since ancient Egypt, but was being bred to the more popular head lettuce by the Dutch. The bitter salads of the chicory and endive types sometimes grew in the wild, and could be gathered during the summer, but gardeners were also beginning to dig up endive roots in autumn, and make them grow pale, new heads in darkness for the winter tables. These various green leaves weren't normally eaten raw in Germany, but were braised or stewed the way spinach often is today. Whole heads of lettuce could also be stuffed and steamed, and the forced endives were very popular braised with a little honey or served as part of a pie-filling.
The popular cabbage family also had some rare members. The cauliflower and the broccoli were just beginning to spread from Italy to the rest of Europe in 1632, and would be found only in the gardens of the keenest gardeners. Brussels sprouts from the Low Countries (now Belgium ) had been around as spruyten/sprouts since medieval times, but they had not yet been bred into producing the small, round balls we know today, and were not very common.
By 1632 asparagus had been grown for about a century in the manor gardens, and could also be gathered in the wild. The wild asparagus was very popular and one of the few plants that even people with major gardens of their own gathered—or rather, had their servants gather—in nature, but gardeners would also harvest the seeds and sow them in their own permanent beds.
Celeriac and celery were only just being developed in Italy, and probably didn't reach Germany for at least a couple of decades after 1632. Potatoes, tomatoes, corn and Jerusalem artichokes had reached Europe from America, but were not yet grown in Germany except as rarities—and then usually considered ornamental plants only.
In addition to the annual vegetables started from seeds every year, most gardens also had some perennials needing a permanent location. In addition to the asparagus mentioned above these plants included most herbs, rhubarbs, artichokes, berry-bushes and fruit trees.
In a small garden it was possible to use the fourth quarter for such a perennial collection, but if the garden was big enough for marginal beds just within the outer fence, then these were the recommended place for plants outside the annual rotation.
A wide range of herbs had been spread all over Europe from the herbal gardens of the cloisters, and by 1632 a average kitchen garden in Germany would contain not just the native horseradish, dill, cress, chives, angelica, caraway, lovage, marjoram and mint, but also the parsley, chervil, thyme, sage, tarragon, and fennel originally imported from—mainly—the Mediterranean area. Those capable of starting plants indoors could also grow basil, and if winter storage was possible also bay and rosemary.
All of the herbs had originally been considered medical plants, but while thyme tea might still be prescribed for a sore throat or caraway seeds for an upset stomach, by 1632 their main use was in the kitchen.
A single herb, the mustard, was used so much that it was grown in small fields, and many herbs could also be gathered in the wild, but to vary the monotone diet even the smallest garden would have a few plants of something flavorful tucked in somewhere. If nothing else there would at least be a few pots or boxes with chives, sage and thyme standing by the kitchen door, but while hanging baskets and window-boxes would certainly have been possible, such were not mentioned in the gardening books, and do not appear on contemporary paintings.
Many of the herbs—such as chives, parsley, chervil and thyme—could be used as edgings for the annual quarters in a small garden, but in a garden with marginal beds it was more common to reserve one or two of these for at least the perennial herbs. Such herbal beds were often laid out to resemble the original beds in the cloisters with each herb having its own little plot surrounded by a narrow row of stepping stones, but it was also common to have one bed with the coarse horseradish, borage, angelica and lovage, and another with rows or plots for the more delicate types. Mints—then as now—were best kept in pots to prevent them from spreading out of control.
In households not able to afford many of the imported spices the importance of the locally grown herbs was so much larger than today, and while some herbs dried very well, there were also a large interest in extending the season of the fresh herbs. Thyme, sage and winter savory would keep their leaves for most of the winter if their position was even slightly sheltered, and the same would rosemary and bay if kept indoors in a cool room with a window. Chives could be planted in pots in the autumn, and moved indoors for forcing in February, while the season for the succulent chervil and parsley could—with some protection—be extended so it lasted for chervil from the end of March to the end of November and for parsley all year round except February. Watercress was also much in demand, as its season started in November and ended in May, but its demand for moisture, and dislike of snow cover, made it difficult to grow.
Fruits and Berries
Other perennials preferably planted in the margin beds included rhubarbs, berry bushes and fruit trees.
Rhubarbs had recently been imported from the Orient, but had quickly grown popular for the early harvest it provided. It was also considered a remedy for the very common gout, but for the gardener its main benefit was that it could be harvested in April-May when the garden produced little else. In the kitchen it was used for savory dishes as often as for sweets.
Berry bushes could either grow free along the outer fences with just a light pruning from time to time, or they could be trained to wires strung between low posts to present a more orderly appearance. Black currant, red currant and gooseberry were the most common bushes, but young plants of raspberries and blackberries could also be dug up in the forests and transplanted into the garden.
The big, succulent modern strawberries had not yet been bred by crossing with the American types, but the small, wild types would be growing wild in the forests, and could be gathered for summer treats by everybody. In the gardens strawberries would spread a bit too willingly to be used as edging, but did fine beneath bushes and trees as an ornamental ground-cover.
Sowing seeds from fruits rarely results in plants producing the same quality as the original fruit, so until hybridizing and grafting became common practice for fruit growing, the quality of the fruit grown around the farms and in town backyards was rather hit or miss. Still, some apple and pear types—such as several Borsdorf and Reinette variations plus the Bergamotte pear—were already being grafted and sold all over central Europe.
The common fruit trees—whether grafted or seed grown—would be on a seed-grown root, and could therefore be expected to grow one or more feet per year, unless kept low by pruning. Such big trees take years to start blooming, but need less protection and nurturing than those grown on a weaker root. And once they do start bearing fruit, a single tree could be expected to produce several barrels of cider.
Apples were by far the most common fruits, and most gardens would have at least one tree. The modern separation into cooking apples, and apples meant to be eaten fresh, wouldn't have made any sense as raw fruit was considered unhealthy, and nearly all apples would be prepared in some way. Instead the apples would be separated into summer apples, that didn't keep for long and were mainly used for cider, and storage apples that could keep well and were either dried or stored in cool cellars and attics.
The most common apple in the German area was the small, round, yellow, red-cheeked Borsdorf from near Meissen in Saxony, a crisp cooking apple with a fresh taste, harvested in October and lasting in storage until after Christmas. Even longer lasting was the larger, pale yellow Reinette Platte from Holstein, also used almost entirely for cooking, but harder, and lasting until spring if stored correctly. Juicier and thus better for cider were the three French apples: Corpen d'Rouge, Orlean's Reinette and Calleville Rouge d'Automne.
If the garden was big enough for more than a single tree, there might be a quince, a mulberry, a prune or a plum tree for more fruits to store fresh or dried for the winter. A row of cherry trees, some pear trees and a walnut tree were also possible, but would take up too much space in most town gardens. A grape vine, on the other hand, could be twining around a post or trained to a trellis, and would be found in vine-growing areas as well as in a sheltered spot in colder areas. Medlars, damsons, hazels and hip-bearing roses were sometimes used as windbreaks, but those fruits could also be gathered from the ordinary field hedges where they had self-seeded.
The Ornamental Features
If the garden wasn't to be devoted entirely to growing vegetables, the most popular ornamental feature would be a path suited for walking in fine shoes and edged with ornamental pots and flowers. Unless the garden was so small that it would look silly—and sometimes also if it did—a small pavilion could be placed in the middle of the path, so that you could sit and look at the flowers. Having a caged songbird hanging in the pavilion would be suited for really impressing the Joneses.
Small trees in handsome pots set at regular intervals along the main path were the most popular and fashionable garden feature. Almond trees and orange trees were the most prized choice, but the gardening books also suggested plants like rosemary shaped to small trees, bay trees, pomegranate, and oleander. If indoor winter-storage wasn't possible then hardy plants like roses trained to small trellises, cherries, or lilacs were suggested instead.
Behind or beneath the row of pots there would be either an entire border of flowers or at the least an edging of the vegetable beds. Among the flowers mentioned snowdrops, crocus, lily-of-the-valley, hyacinths, tulips, daffodils, Lenten roses, irises, cannas, martagon lilies, snapdragons, gladiolus, marigolds and larkspurs were especially recommended, but for those who had to make do with what seeds they could gather in the wild violets, daisies, feverfew, columbines, lupines, foxgloves, cornflowers and poppies would also make a good display.
A central seating area was supposed to have a roof or at least a canopy to provide some shade. There should also be climbing plants such as sweet peas, clematis or morning glory, or best of all, climbing roses which could be bought from special nurseries or local estates. This would also be the place where the first tomatoes and red-flowered runner beans would have been grown, but if nothing else was available then an ordinary grape vine would do. Using the poles around a seating area to support the long stems of the hops grown for beer making was, however, not a good idea, as the abrasive surface of the stems tended to cause a rash.
If a seating area was not wanted in the formal walk, then a medieval knot garden would be a popular choice. A knot garden is a pattern of low clipped box hedges, planted and cut to resemble rope tied as a loose knot. The spaces in between the hedges would originally be filled with finely raked colored sand, rather than herbs or roses as later became the fashion, but letting the box-plants on the corners grow larger than the rest and cut them to topiary shapes remained popular.
The Non-hardy Plants
In the estate gardens the gardeners would be growing melon plants and cucumbers, and—if a new orangery had been build—also oranges and lemons in containers to be moved inside for the winter. In the more common gardens an adventurous gardener might try for the melons in a cold frame, and sow some snapdragon seed in a cool window, and if a cool cellar—preferably with a window—with room for plants were available, it might also be possible to keep some of the highly popular small almond trees. Orange and lemon trees don't shed their leaves and go dormant during the winter, so to grow those successfully a room with a glazed window was necessary. Fig, apricot, and peach trees usually grew too big to move around, but it was possible to get them to survive in a sheltered corner by winter-wrapping them in old blankets.
Tools and the Basic Work-Schedule
The basic tools available to 1632 gardeners were fairly much the same as found in a garden shed today. There would be rakes of wood and metal, hoes, strong spades, dandelion irons, small hand trowels, secateurs, saws, knives, hammers, strings, sticks, and watering cans with shower spouts. The main difference—aside from the absence of any power tools—would be that as many tools as possible were carved out of wood, rather than being made of metals.
The basic work would also be fairly much the same. There would be preparing the soil by digging and fertilizing the beds, pruning and grafting, sowing and planting, watering, weeding and pest control, and finally harvesting. The differences would be that fertilizing would be entirely organic and use both human and animal waste, that all grafting would probably be done by somebody local who happened to have the skill, that sowing would be done according to tables linked to the moon-phases, and that pest control would be limited to substances like nettle-water and tobacco tea. In other words: the kind of gardening now called organic, biodynamic, etc.
There would probably also be a much higher tolerance for what is today considered weeds. In the earliest spring when the tired kale and perhaps a few turnips were the only remaining vegetables, the first new green sprouts and leaves were most eagerly awaited by everyone. In the kailyards fresh leaves of parsley and chervil might be gathered, and the young sprouts of hop were tender enough to eat, but most of the earliest eatable plants were weeds such as dandelions, nettles, ground elder and dock, and however much they were hated during the summer, they were valued in spring for the early edible greens they produced. Angelica, wild asparagus, wild garlic, and watercress were also quick to sprout, and while they could be gathered in forests and meadows, some gardeners also dug up the roots and gave them a corner or a marginal bed for easy access.
During the centuries between 1632 and 2000 much has been discovered about plants and their cultivation, many new plants have been bred, and many new gardening styles and methods invented. Despite Grantville having no specialty seed store, it is certain that many new plants would have come with the town, and eventually spread across Europe. Modern knowledge about hybridizing and grafting techniques would also have been accepted by local gardeners, and once artificial fertilizers, biocides, and lighter, more durable tools went into production, these would have been bought by those who could afford them.
The purely theoretical knowledge about plants, their anatomy, genetics, and systematic classification, would at first seem of interest only to a few European scholars. However, sooner or later most keen gardeners try crossing a few plants, and even that most basic genetic knowledge: that the best new results often don't occur until the second generation, would have been a major discovery. Knowing why crop-rotations worked, and why grafting sometimes didn't, would also be of interest to especially head-gardeners at castles and manor houses—many of whom had a side-business producing plants such as roses and fruit trees for sale.
Changes in gardening styles would probably have come about very slowly, as the main purpose of most gardens was production with any stylish concerns coming a very distant second. A few of the wealthiest royals and nobilities might have redone a garden in French or Italian baroque style, or tried for an English landscape garden, but to most people their garden had to produce the vegetables they needed with as little time and money spent as possible.
Some of the intensive methods popular in modern times, with raised beds, etc., are likely to gain a following—especially as industrialization gains speed and both truck-gardening and allotments became relevant. University students and other people without an independent household had generally rented rooms without kitchen access and eaten their meal in taverns, but an infrastructure able to support the families of industrial workers living in apartment blocks would not be something just occurring overnight. There would also be the more psychological aspect of how a “proper” household was defined, and that would to the large majority of the new workers include at least a rented plot of land for a kailyard.
A few plants were likely to spread far and fast, and first, last and always would have been the potato. Potatoes along with many other American plants had already arrived in Europe, but they were being regarded as curiosa or grown as ornamental plants in manor gardens. To have an entire group of influential new people spread all over Europe taking potatoes for granted as a part of their daily diet, missing them when not available, and mentioning how easy and reliable a crop they made, was bound to have gardeners and farmers wanting to try growing them. Potatoes obviously would have potential as a field crop—especially on poor soil—but few gardeners would be able to resist growing a tasty vegetable, which would reliably produce a crop from midsummer onwards to the autumn, and could be stored without problems all winter.
The second fastest group of plants to spread would probably have been the modern continuously-blooming roses. Roses were hugely popular and a major status symbol, but the only types available were those now called historical roses. Historical roses have wonderful fragrances, but they blooms only for about a month every year, and their color-scale is fairly much limited to pink, red and white. An owner of a modern bright yellow climbing rose would literally be able to set any price he wanted on his spring cuttings. Rose cuttings must be grafted immediately after cutting and transported as whole living plants, which would be expensive, but once the wealthiest household in an area had a rose, it was of course much easier for the rose to spread to the entire region.
Fruit trees were already being grafted all over Europe, and while most gardeners made do with the locally available types, there was also a certain amount of international trading going on. That the cuttings used for grafting are cut in winter or very early spring, while the trees are still dormant, means that there are a few months every year where a bundle of fruit tree cuttings may be wrapped in burlap and transported easily by wagon. At their destination, the cuttings would be grafted onto a locally grown root and eventually become a French pear in Germany or a German apple in France. That the fruit tree cutting could be moved so easily, meant that they were available also to people of only moderate means—such as village parsons or small town craft masters—and at least some of the traders leaving Grantville around the month of March would certainly have a bundle of cuttings tucked beneath their wagon seat to sell along their route.
Other vegetables, herbs and ornamental plants would eventually spread from Grantville as well, but as with the potatoes the main impact would probably come simply from Americans mentioning them abroad, and thus creating a demand. The Grantville plant stock would of course have had several centuries of breeding for improvement, but without people to advocate the growing of, for example, tomatoes, corn, peanuts, chiles, and pumpkins, these would have remain curiosa for decades if not centuries.
How soon and how many items intended for especially for gardens would go into production is anybody's guess, but as in our world it would probably follow the farming items. Artificial fertilizers and more efficient pesticides would immediately have a market, but Victorian glass cloches and mobile watering wagons would also set local gardeners drooling. In fact anything able to increase a garden's yield or—as servants became industrial workers—save labor, would have a market.