Measure the real sun, not the sun you imagine
The first mistake is deciding a border's exposure by looking at it in mid-morning. A corner may receive six hours of direct sun between April and September and barely two in December, when the sun travels lower and the shadow of the building or wall stretches further. That difference explains why a plant labelled sun-tolerant looks wilted in winter and why a shade plant scorches in May.
The practical approach is to watch the full path at three points in the year: spring, high summer and autumn. Simply note, without complicated instruments, what time light enters each area and when it disappears. If you cannot wait months, at least draw a plan with the fixed obstacles, walls, trees and pergolas, and work out the shadow cast at midday and late afternoon.
Another common error is confusing brightness with direct sun. A whitewashed courtyard can be very bright and yet receive no direct radiation at any hour. Many partial-shade plants tolerate that diffuse light, but they will not tolerate strong western sun, which on the coast arrives with salty air and dries quickly.
- Note the exposure of each area in spring, summer and autumn before planting.
- Distinguish between diffuse light, morning sun and strong afternoon sun: they are not equivalent.
Planting by habit rather than by orientation
It is common to repeat the same species throughout a garden because it worked in another house or looked splendid in a nearby development. The mistake is not the plant but ignoring that two metres can change its behaviour. A myrtle or a rosemary in full midday sun inland may cope well; on the front line of the coast, with salty breeze and shallower soil, the same specimen may show faded leaves if it is not acclimatised.
The right decision starts with observing what already grows spontaneously nearby. If the natural vegetation of the corner has small, leathery leaves, it is probably a spot of strong sun and little moisture. If large, green leaves dominate, there is more moisture and less direct radiation. Reading the place this way prevents most failed transplantings.
It also pays to avoid placing shade plants under eaves that receive sun reflected from the facade. The reflection increases radiation and heat, and an understorey plant can scorch even under an overcast sky. By contrast, a sun plant set in the shelter of an east-facing wall usually develops better than one in full midday sun.
- Look at the nearby spontaneous vegetation: it shows the real microclimate.
- Sun reflected from pale walls counts as strong exposure, even without direct sun.
Failing to plan for growing shade
A very common planning error is designing the planting around the current size of the trees. A young specimen of medium size may cast modest shade in its first years and, within a decade, cover the whole border. When that happens, the sun plants placed beneath lose vigour, stretch and stop flowering. Correcting it later means transplanting or pruning the tree more aggressively than you would like.
The prudent approach is to reserve areas of future shade for species that tolerate it, and keep full sun in areas that need renewing each season. If you want a dense, low hedge next to a tree that will grow, choose species that accept partial shade and do not rely on constant pruning to keep it.
On the Costa del Sol, the shade of a tree does more than reduce radiation: it also lowers soil temperature and reduces evaporation. Planting heat-sensitive species on the west side of a building with no projected shade is one of the most repeated causes of water stress in summer.
- Draw the shade the adult tree will cast, not that of the newly planted specimen.
- Reserve full-sun areas for plants that need renewing or pruning each year.
Watering the same everywhere regardless of exposure
Once planting is established, irrigation is often programmed by zones rather than by exposure. This is a frequent error: a sprinkler covering a border in full sun and another beside a shaded wall receive the same amount, although water demand is very different. The result is excess water in the shaded zone, with suffocated roots and fungi, and a shortfall in the sunny zone.
The practical approach is to separate irrigation sectors by exposure and soil type. Full-sun areas need more frequent checks in summer, especially if the soil is sandy and drains quickly. Shaded areas, by contrast, hold moisture longer and should be watered less often, checking first by hand or with a stick whether the substrate is really dry.
It is also a mistake to water at midday in high summer in the belief that it refreshes the plant. Much of the water is lost to evaporation and wet leaves can suffer in strong sun. Watering at dawn or dusk, and directing water to the soil, reduces losses and prevents scorching.
- Divide irrigation by exposure: do not mix full sun and shade in the same sector.
- Check soil moisture before watering in shaded areas.
Pruning without thinking about the light that gets in
Pruning changes the exposure of whatever lies beneath. A common error is to thin a tree or hedge too much in a single winter: the interior, accustomed to shade, suddenly receives direct sun and can suffer scorch on bark and leaves. This often happens with dense hedges and with shrubs cut back hard to rejuvenate them.
The sensible decision is to thin gradually, spreading the work over two or three seasons, and leave enough cover for the interior to adapt. If the canopy must be reduced a lot, do it at the end of winter, when the plant can regrow with energy and the sun is not yet intense. In autumn, heavy pruning leaves the specimen exposed to cold nights and rain without leafy protection.
In inland gardens of the province, with colder nights, heavy autumn pruning can delay regrowth. On the coast, the main risk is desiccation from wind and sun after excessive pruning. In both cases the criterion is the same: prune with the light that will reach the soil in mind, not only the shape of the shrub.
- Thin canopies gradually so the interior adapts to more light.
- Avoid heavy autumn pruning if the specimen will be exposed to sun and wind.
Ignoring the effect of the facade and the soil
Two gardens with the same orientation can behave differently because of the facade and the soil. A pale south-facing wall reflects light and heat, creating a drier, brighter microclimate than the rest of the garden. Shade plants are often placed there because the corner seems sheltered, and then dehydrate. By contrast, dark soil or thick mulch retains less heat and may allow slightly more delicate species.
The underlying error is treating orientation as a single label. In practice, observe how a test plant behaves for a season before spreading the same species throughout the garden. That simple trial saves repeat purchases and transplantings.
For those who work with these decisions daily, as happens in Gardening in Sotogrande, the useful habit is to review exposure after every building project or change of garden furniture. A new pergola, an awning or a growing hedge can turn a sunny corner into a shaded one in a single season, and plants do not always adapt to that change unaided.
- Review exposure after installing pergolas, awnings or new hedges.
- Use a test plant in doubtful corners before repeating the same species.