Commercial Parking Lot Island Maintenance

The hardest growing conditions on the property

Parking islands look like small planting beds. They are closer to containers, and they are the harshest environment on a commercial site.

Heat is the first problem. Asphalt on all sides absorbs sun all day and radiates it back into the island, which runs substantially hotter than the same planting twenty feet away in open ground.

Soil is the second. Islands are usually backfilled with whatever was available during construction and then compacted by the same equipment that laid the paving. Water does not penetrate it and roots cannot spread.

Volume is the third. There is only so much soil in an island, and a tree planted in one is working with a fraction of the root space it would have anywhere else.

sides of radiating asphalt on a typical island

3sides of radiating asphalt on a typical island

root space available beyond the island edge

0root space available beyond the island edge

irrigation zone usually shared with somewhere entirely different

1irrigation zone usually shared with somewhere entirely different

Islands and the irrigation they usually do not have

Parking islands are the most common place to find planting on the wrong irrigation zone, or on no working zone at all.

The heads sit in the path of cars and get clipped, tilted, or crushed. Because each island is small, one broken head can be the entire coverage for that island, and nobody notices until the planting dies.

The other pattern is islands sharing a zone with a lawn area. Turf run times drown island shrubs in winter and starve them in summer, because their needs are opposite.

Islands deserve their own zone and heads placed out of the wheel path. Where that is not achievable, drip is usually the better answer.

What survives in an island

The plants that succeed in parking islands are the ones that tolerate heat, poor soil, and irregular water, which is a much shorter list than the plants that tolerate any one of those.

Structure matters more than flowers. An island that reads as deliberate with three tough shrubs and good mulch looks better year round than one attempting a display and failing for four months of it.

Trees in islands need particular thought. The species has to accept restricted root space, and the location has to accept what its roots will eventually do to the surrounding pavement. That combination rules out most of what was traditionally planted in them.

Where an island has failed repeatedly, the honest answer is often to stop replanting and change the approach: heavier mulch, tougher species, or hard surface with a single tree rather than a bed that never works.