Vegetation

Types of illumination

Floodlights aimed upwards make the tree crown appear three-dimensional. Two floodlights from the front, yet to the side, illuminate the crown evenly as a voluminous mass, while floodlights mounted at the side add greater emphasis to the three-dimensionality. Floodlights arranged around three sides illuminate the crown evenly from all sides and reduce the three-dimensionality of the tree form. Floodlights in the background create back-lighting and make the tree crown into a silhouette Uplights at the trunk accentuate the trunk as a linear feature and visually connect the crown to the ground. Depending on the season, light from above will either emphasise the contour of the crown or accentuate the shadows of the branch structure on the ground.

Luminaires arranged on several sides give an even illumination of the tree, while one or two luminaires create a greater three-dimensional effect. Narrow-beamed uplights are suitable for highlighting any striking, tall tree trunks. The texture of the bark is brought out stronger when lighting from the front. Positioning the luminaires to the side gives rise to a narrow line of light on the trunk. When illuminating a wall behind a tree, the silhouette of the crown and trunk becomes apparent. Spotlights mounted in atria or on facades can cast the contour of the tree and/or branches as a shadow on the ground.

Tree growth

One or two luminaires accentuate trees of small dimensions. Several floodlights produce an even illumination of large, fully grown trees.

Season

Floodlit illumination of the tree crown particularly brings out the beauty of the outermost blossom in the springtime. In the summer, the dense foliage makes the crown appear as a solid mass. Coloured leaves are characteristic for the autumn. In the winter, the lighting effect is reduced to the filigree branch work.

Lamp selection is a factor that influences the colour of light and the colour rendition of the leaves and blossom. Daylight white colours of light emphasise blue-green foliage colours, whereas warm white colours of light accentuate brownish-red leaves.

Floodlit illumination emphasises the shape of the tree crown as a solid volume. Positioning the luminaires close to the tree underlines with grazing light the texture of the crown and of the trunk. The illumination from below brings out the three-dimensionality of the crown when the foliage is quite open.

Rounded, weeping trees with dense, low hanging foliage that cannot be seen through, lend themselves to floodlit illumination and the luminaires are best positioned outside the area under the tree. On spreading trees with thin, see-through foliage, illuminating from within the area under the tree, using uplights allows the whole tree crown to appear aglitter. Illuminating a tree with grazing light requires a flat incident beam at approximately 15 degrees. Spherical trees require a greater distance between luminaire and crown than columnar trees do here. Narrow-beamed uplights are particularly suitable for lighting high palms. The desired illuminance must be selected to suit the reflectance of the leaves.

Luminaires

Floodlights located in front illuminate the tree crowns evenly. Floodlights positioned at the sides produce a hard contrast of light and shadow. Luminaires on two sides avoid hard shadows. Uplights at the trunk emphasise the trunk as a vertical linear feature.

Having several luminaires with high cut-off angles reduces the glare compared to a few broad-beamed luminaires. Narrow-beamed and well-aimed luminaires reduce the superfluous emission of light into the surroundings. The decentralised illumination of trees allows a differentiated lighting of a cluster of trees. Spotlights are suitable for additional highlights. Tree growth and the avoidance of glare are to be considered when positioning and aiming the luminaires.

Light distribution

The cluster of trees can be visually differentiated by using different luminaires and differently aimed. Spatial depth is created by adding lighting emphasis in the foreground, middle ground and background. Stronger brightness contrasts support this effect. Narrow-beamed luminaires provide highlighting, while broad-beamed floodlights take on the task of general lighting.

Upwardly directed spotlights emphasise the tree canopy. Floodlights with asymmetric light distribution give homogenous light from base to canopy even on tall and broad rows of trees. Narrow-beamed uplights highlight the tree trunk as a vertical, linear feature .

The effectiveness of rows of trees to delineate space depends to a very large extent on the type of tree. Thus, depending on the type of tree, a closely planted row of trees can appear as a 'wall' or a 'colonnade'. Narrow-beamed and well-aimed luminaires reduce the glare and the spill light into the surroundings. The tree growth must be considered when positioning and aiming the luminaires.

Upwardly directed spotlights emphasise the tree crowns. Floodlights with asymmetric light distribution give homogenous lighting from base to canopy even on extensive avenues of tall trees. Narrow-beamed uplights highlight the tree trunk as a vertical, linear feature.

The spatial profile of tree-lined avenues depends to a very large extent on the type of tree. Thus, depending on the type of trees, an avenue of narrowly spaced trees can act as a wall and segregate a definite area or can appear as a colonnade. Narrow-beamed and well-aimed luminaires reduce the glare and spill light into the surroundings. The tree growth must be considered when positioning and aiming the luminaires.

Broad, upwardly directed beams of light emphasise the underside of the tree canopy. Narrow-beamed uplights highlight the tree trunk as a vertical, linear feature.

The tree crowns of narrowly spaced trees combine to take on the effect of a canopy. Having several narrow-beamed luminaires reduces the glare compared to a few broad-beamed luminaires. On pathways and traffic routes, it must be ensured that the luminaires are well shielded to prevent glare.