In Denmark, poor growth conditions for urban trees have been perceived as a problem since the 1980s. Restricted planting-pit sizes are mainly responsible for this problem. To increase the volume of the planting pit, several materials have been introduced to mix with soil to allow root growth under pavements. Three methods are available for installing these materials under pavements. During the last 5 years, more than 800 trees have been planted on more than 30 sites using these materials and installation methods.
Every method has advantages and disadvantages.
No serious difficulties due to load-bearing capacity or frost heaves have been recorded. Progeny Testing in Street Trees Subjected to Roadside Soil Pollution by Oddmund Fostad and Per Anker Pedersen Abstract . Stunting in roadside soil was greatest in A. platanoides and least in B. pendula . In A. platanoides , a significant correlation between height of the seedlings and vigor of the mother trees was found in 1993 but not in 1992. In A. hippocastanum, a correlation was found in both years.