Land & Growing Handbook

Soil pH is the single most important chemical property of your soil. It controls whether nutrients are locked up or freely available to plants — even fertile soil can starve crops if the pH is wrong. The scale runs from 0 (most acidic) to 14 (most alkaline), with 7.0 being perfectly neutral.

Most vegetable crops, herbs, and fruit trees perform best between pH 6.0 and 7.0. In this range, macronutrients like nitrogen, phosphorus, and potassium are all accessible, and beneficial soil microbes are most active. Below 5.5, aluminum and manganese can reach toxic levels; above 7.5, iron, manganese, and zinc become insoluble and deficiencies appear even in well-amended soil.

Some plants are deliberate exceptions. Blueberries and lingonberries prefer pH 4.5–5.5. Lavender and rosemary tolerate alkaline soils up to pH 8.0. Understanding these preferences lets you cluster acid-loving plants in naturally acidic patches rather than fighting your soil everywhere.

Growplot uses your polygon's mapped soil pH to pre-filter species by their optimal and acceptable pH ranges. Species shown as a strong match have overlapping pH tolerances with your land. You can shift your pH downward with elemental sulfur or acidic mulches (pine bark, coffee grounds), and raise it with agricultural lime or wood ash — but changes take months and should be tested before large-scale application.

Soil texture is determined by the relative proportions of three particle sizes: sand (0.05–2 mm), silt (0.002–0.05 mm), and clay (below 0.002 mm). These proportions are plotted on the USDA soil texture triangle to assign one of 12 texture classes — from sand and loamy sand through silt loam and clay loam to heavy clay.

Loam and its variants (sandy loam, silty clay loam) are considered ideal for most food production because they balance drainage, water retention, and aeration. Sandy soils warm up faster in spring and are easy to work, but nutrients leach out quickly after rain. Clay soils hold water and nutrients well but can become waterlogged, compacted, and difficult to till when wet.

Texture directly determines which plants will thrive without intervention. Taprooted crops like carrots and parsnips need loose, deep soil — heavy clay stunts and forks them. Mediterranean herbs like rosemary and thyme evolved in rocky, fast-draining soils and rot in waterlogged clay. Wetland species and some brassicas, on the other hand, tolerate or even prefer heavier soils.

Growplot reads SoilGrids texture data for your exact polygon and uses it to match species by drainage preference. You can improve texture over time by adding organic matter — compost improves both clay and sandy soils, increasing aggregation in clay and water-holding capacity in sand. Texture class itself changes very slowly; working with your existing texture is usually more practical than trying to change it.

Developed by climatologist Wladimir Köppen in 1884 and refined over the following century, the Köppen system remains the most widely used climate classification. It uses monthly temperature and precipitation data to assign each location a 2–3 letter code — for example, Cfb (oceanic temperate with no dry season) or BSk (cold semi-arid steppe).

The five primary categories reflect the dominant growing environment. Type A climates (Af, Am, Aw) are frost-free with high year-round rainfall — ideal for tropical perennials, bananas, and papayas. Type B climates (BWh, BWk, BSh, BSk) are defined by aridity and suit drought-adapted species like pomegranates, figs, and many Mediterranean herbs. Type C climates (Cfa, Cfb, Csa, Csb, Cwa, Cwb) cover most of the world's productive farmland — temperate with mild winters and distinct seasons. Type D climates (Dfa, Dfb, Dfc, Dwa, Dwb) bring cold winters with snow cover, suited to cold-hardy fruits like apples, pears, and stone fruits. Type E climates (ET, EF) have no true growing season.

The third letter adds precision: 'f' means no dry season, 's' means a dry summer, 'w' means a dry winter, 'a' means hot summers, 'b' means warm summers, 'c' means cool short summers. This granularity matters — a Csa zone (hot-summer Mediterranean) will suit olive trees and grapes far better than a Cfb (oceanic) zone at the same latitude.

Growplot maps your polygon to a Köppen zone using a global raster dataset and filters the species catalog to those whose native or adapted climate range includes your zone. This ensures species recommendations reflect long-term climate reality, not just current conditions.

Elevation shapes the microclimate of your land more than any other single topographic factor. The environmental lapse rate — approximately 0.65°C per 100 metres of altitude gain — means that a farm at 800m is roughly 5°C cooler on average than one at sea level in the same region. Over a season, this is the difference between growing maize and growing only cool-season brassicas.

Frost risk increases significantly with elevation. At 500m above sea level in a temperate zone, you may have 30–60 fewer frost-free days than valley floor farms nearby. At 1,500m, the growing season may be half that of lowland areas. Cold air is denser and drains downhill at night, so valleys can experience ground frost even when hillside orchards nearby stay above freezing — an effect called cold air pooling.

Elevation also affects UV radiation, wind exposure, and relative humidity. Above 1,000m, UV intensity increases and crops that evolved at lower altitudes can suffer leaf scorch. Wind speeds are typically higher on exposed ridgelines, increasing evapotranspiration and physical stress on tall crops and fruit trees.

Growplot reads elevation from NASA SRTM data for your polygon's centroid and uses it in combination with Köppen zone to refine species matching. Species with cold tolerance thresholds are filtered against your estimated minimum winter temperature, which is derived from regional baseline temperature adjusted for your elevation. This means crops that look suitable by zone alone may still be excluded if your elevation pushes temperatures below their survival threshold.

Slope and aspect together define the solar geometry of your land — how much sunlight it intercepts, from which direction, and across how many hours of the day. A 15° south-facing slope in the northern hemisphere receives solar radiation nearly equivalent to land 300km further south. The same slope facing north may receive 30–50% less solar energy, creating a dramatically different growing environment within a few metres.

Aspect is measured in compass degrees: 0° is north, 90° is east, 180° is south, 270° is west. South-facing (135°–225°) slopes are warmest and driest in the northern hemisphere — ideal for heat-loving crops like grapes, tomatoes, peppers, and many Mediterranean herbs. North-facing slopes stay cool and moist, benefiting shade-tolerant crops, woodland species, and leafy greens that bolt in heat. East-facing slopes receive morning sun with afternoon shade, while west-facing slopes heat up later but stay warm into the evening.

Slope angle affects drainage and erosion risk. Slopes under 5° drain gently and allow machinery use. Between 5° and 15° are suitable for contour planting, swales, and terracing. Above 20°, erosion management becomes critical and perennial cover crops or tree systems are preferred over annuals. Very steep slopes (above 30°) are generally unsuitable for cultivation and better suited to forestry or wild habitat.

Growplot uses slope and aspect data derived from NASA SRTM elevation data for your drawn polygon. Aspect influences species matching by flagging sun-hungry species as less suitable on poleward-facing slopes, and helps identify whether your land is prone to frost pockets (flat, sheltered areas at slope bases) or wind exposure (ridge crests and steep upper slopes).

Originally developed by the USDA in 1960 and last updated in 2023, the Plant Hardiness Zone Map is the standard reference for determining which perennial plants can survive winter in a given location. The map divides temperatures into 13 main zones (1–13), each subdivided into 'a' (colder half) and 'b' (warmer half), giving 26 zones total plus zone 13b — 27 zones in all.

Zone 1a, the coldest, represents areas where minimum winter temperatures drop below -51°C (-60°F), found in interior Alaska and northern Canada. Zone 13b, the warmest, covers tropical lowlands where minimum temperatures never drop below 21°C (70°F). Most of the world's productive farmland falls in zones 4–9. Zone 5b, for example, represents minimum winter temperatures of -26°C to -23°C and is the edge of cold hardiness for many fruit trees like peaches and sweet cherries.

Hardiness zone is critical for perennials — trees, shrubs, herbaceous perennials, and bulbs that need to survive multiple winters. Annuals are not constrained by hardiness zone in the same way, as they complete their lifecycle within one season. However, the zone still informs your last and first frost dates, which bound the annual growing season.

Growplot maps your polygon to a hardiness zone using global minimum temperature data and uses it to filter perennial species by their cold hardiness rating. A fruit tree listed as hardy to zone 6 will not appear as a match if your land falls in zone 5. This protects you from planting long-lived trees that would be killed in the first cold winter — one of the most costly mistakes in orchard and food forest establishment.

Companion planting draws on centuries of traditional agricultural knowledge formalized through modern research. At its core, it recognises that plants are not passive — they release root exudates, volatile compounds, and physical structures that affect their neighbours. Relationships can be positive (companions), negative (antagonists), or neutral, and they vary in mechanism and strength.

Growplot uses six relationship types: 'companion' (general benefit, often multiple mechanisms), 'pest_repellent' (one plant deters pests of the other), 'pollinator_attractor' (draws pollinators benefiting nearby crops), 'nitrogen_fixer' (legumes or other fixers feeding neighbours through root release), 'trap_crop' (sacrificial plant that draws pests away), and 'allelopathic' (one plant chemically suppresses the other — a negative relationship to avoid). Relationship strength is rated 1 (weak evidence) to 5 (well-documented, reproducible). Confidence reflects the quality of research behind the pairing.

One important spatial factor is minimum distance: some relationships only function or are only safe beyond a certain proximity. The juglone flag marks species affected by the allelopathic compound juglone released by black walnut roots — these must be planted well outside the drip line. Relationships marked 'bidirectional' mean both plants benefit; unidirectional relationships benefit only one partner.

In Growplot's farm designer, companion relationships appear as visual indicators when you place species on the canvas. Species with strong positive relationships are highlighted; antagonistic pairs trigger a warning. This lets you build plant guilds — clusters of mutually supportive species that together provide more ecosystem services than any single plant alone.

The food forest model, popularised by Robert Hart in the 1980s and developed further by practitioners like Martin Crawford and Dave Jacke, organises plants into vertical strata that mirror the layered structure of a natural forest ecosystem. Unlike a monoculture orchard or vegetable bed, a well-designed food forest becomes increasingly self-sustaining over time as the layers establish and interact.

The nine layers are: Canopy (tall trees 10–30m+, e.g. oak, walnut, full-size apple), Sub-Canopy (small trees 4–10m, e.g. pear, plum, elder), Shrub (woody perennials 1–4m, e.g. currants, gooseberries, rosemary), Herbaceous (non-woody perennials and annuals, e.g. comfrey, yarrow, vegetables), Ground Cover (low-growing spreaders that suppress weeds, e.g. creeping thyme, strawberry), Climber (vining plants that use vertical structures, e.g. kiwi, grape, climbing bean), Rhizosphere (root crops harvested from soil, e.g. horseradish, burdock, Jerusalem artichoke), Understory (shade-tolerant species under the canopy, e.g. ferns, woodland herbs), and Root (true underground crops and fungi including mushroom cultivation).

Successful food forest design requires understanding light competition across layers. Canopy trees cast shade that benefits moisture-loving understory species but excludes sun-hungry herbaceous crops. Timing matters too — early-successional species like comfrey and nitrogen-fixing shrubs are planted first to build soil and create shelter for the slower-growing tree layers. The system is designed for permanence: a mature food forest at year 20 looks very different from year 2.

Growplot uses layer assignment to help you visualise vertical stacking in the farm designer and to flag potential light conflicts between species. When you add a canopy tree, the system automatically considers which sub-canopy, shrub, and ground cover species are shade-compatible beneath it, making it easier to build a coherent guild without inadvertently planting sun-lovers under dense canopy.

Crop rotation is one of the oldest and most evidence-backed practices in agricultural science. Its principles are simple: different plant families take up different nutrients, host different soil pathogens, and interact differently with soil biology. By moving families around, you prevent the build-up of specialist pests and diseases while allowing soil to recover between demanding crops.

The standard rotation grouping uses botanical families rather than individual crops. The four main groups in a classic European rotation are: Solanaceae (tomatoes, peppers, aubergines, potatoes) — heavy feeders prone to blight; Brassicaceae (cabbages, kale, broccoli, radishes, turnips) — prone to clubroot and cabbage root fly; Leguminosae (peas, beans, clover) — nitrogen fixers that improve soil for the following crop; and Roots/Alliums (carrots, parsnips, onions, leeks, beetroot) — lighter feeders that follow the hungry brassicas or solanaceae. A typical 4-bed rotation moves each group forward one bed each year, so no family occupies the same bed more than once in four years.

Some pathogens require longer breaks. Clubroot (Plasmodiophora brassicae) can persist in soil for 20 years; once present, brassica-free periods of 5–7 years are recommended. Potato cyst nematodes similarly build up under continuous potato cropping and require a minimum 4-year break. This is why tracking rotation history — not just planning future rotations — matters for long-term soil health.

Growplot assigns each species a rotation family and, in the farm designer, can alert you when you're planning to repeat a family in the same bed within the recommended cycle. Combined with the journal feature for logging past plantings, this gives you an evidence-based rotation record rather than relying on memory across multiple growing seasons.

The zone model, central to Bill Mollison and David Holmgren's permaculture design system, is fundamentally a tool for minimising unnecessary energy expenditure — your energy, not just fuel. It works from a simple insight: the more frequently you need to visit something, the closer it should be to your home base. This principle applies equally to a half-acre back garden and a 50-hectare farm.

Zone 0 is the house itself — the centre of human activity, energy consumption, and daily decision-making. Zone 1 is immediately adjacent to the house and is visited multiple times a day. It contains salad crops, herbs, seedling nurseries, and anything requiring daily harvest or monitoring. Zone 2 is visited once or twice daily and contains main vegetable beds, small fruit bushes, chickens, and compost systems. Zone 3 covers the main farm area — staple crops, orchards, larger livestock — visited once a day or a few times per week. Zone 4 is semi-wild: managed woodland, forage crops, and timber trees that need occasional intervention but are otherwise self-sustaining. Zone 5 is the wild zone — left entirely unmanaged as habitat, seed bank, and inspiration. No zone 5 means no space for natural processes to operate.

The boundaries between zones are not fixed geometric rings but are shaped by the actual paths you walk, the gates you pass through, and the terrain. A steep slope behind the house may push zone 2 plantings to the flat area 50 metres away rather than on gradient directly adjacent. Water sources, shelterbelts, and microclimates all influence where zone boundaries fall in practice.

Growplot uses zone information as a design layer in the farm planner. When you assign species to zones, it helps you prioritise what to establish first (zone 1 pays back fastest), plan access paths, and understand why high-maintenance crops like salad greens should be close to the kitchen rather than at the far end of the property.

Water is typically the primary limiting resource for plant growth — more so than nutrients in most non-waterlogged soils. A plant's water need rating reflects its evolutionary adaptation to moisture availability and its physiological demands during the growing season. It is not a fixed number but a relative classification that interacts with your local rainfall, soil texture, and microclimate.

Low water need (drought-tolerant) species evolved in semi-arid or Mediterranean climates and have structural or physiological adaptations — deep taproots, waxy or silver leaves, CAM photosynthesis, or bulbs that go dormant in summer. Lavender, rosemary, fig, pomegranate, and many alliums are in this category. Once established (typically after 2–3 growing seasons), they need little to no supplemental irrigation in temperate climates. Medium water need species — most temperate fruits, many vegetables, comfrey, and herbs — perform well with natural rainfall in humid climates but need watering during extended dry periods. High water need species — leafy greens, celery, cucumbers, many brassicas — have shallow root systems and high transpiration rates and need consistent soil moisture to avoid bolting, wilting, or poor yields.

Water need interacts strongly with soil texture. Sandy soils drain fast and need more frequent irrigation even for drought-tolerant species during establishment. Clay soils hold water longer, reducing irrigation frequency for medium and low-need species but increasing waterlogging risk for drought-adapted plants. Mulching — a 5–10cm layer of wood chip, straw, or leaf mould — reduces evaporation and can halve irrigation requirements across all water need categories.

Growplot uses water need ratings alongside your soil texture and Köppen zone to rank species by how well they suit your site's natural moisture regime. Species rated as drought-tolerant will be flagged as well-suited to dry zones or sandy soils even where rainfall is low. High water need species in low-rainfall zones will be flagged as requiring irrigation infrastructure before they are practical choices.

Sunlight duration and intensity drive photosynthesis, flowering, fruiting, and the concentration of sugars and essential oils in crops. Sun requirements are a practical shorthand for how much daily solar radiation a species needs to complete its lifecycle and produce a worthwhile yield. They are measured in hours of direct (unobstructed) sunlight per day averaged across the growing season.

Full sun species (6+ hours daily) include almost all fruiting vegetables — tomatoes, peppers, cucumbers, courgettes, squash — along with most grain crops, sun-loving herbs like basil and oregano, and the majority of fruit trees. Without adequate direct sun, these crops produce poor yields, become leggy, have increased disease susceptibility, and in the case of fruit trees, may fail to set fruit entirely. On south-facing walls and slopes, reflective surfaces can amplify solar gain, allowing full-sun crops to succeed even in marginal climates.

Partial sun/shade species (3–6 hours) include many brassicas, salad greens, chard, spinach, peas, mint, and woodland edge fruits like redcurrants and gooseberries. These plants often benefit from afternoon shade in hot climates, which prevents bolting and leaf scorch. In dappled light under deciduous fruit trees, they can be highly productive — the basis of the understory layer in food forest design.

Full shade species (under 3 hours) are woodland plants: wild garlic, wood sorrel, ferns, sweet cicely, and many medicinal herbs. They have evolved to photosynthesise efficiently under canopy conditions and may actually be damaged by prolonged direct sun exposure. Cultivating shade-tolerant species under established trees makes productive use of land that would otherwise be bare ground.

Growplot combines sun requirement ratings with your polygon's aspect and estimated canopy cover to match species to the actual light conditions on your land. A north-facing slope or a site with existing mature trees will score shade-tolerant species more highly, while open south-facing land will prioritise full-sun crops and fruiting species.