Sidewalk with adjacent ornamental grass plantings

People love lush landscapes and instant gratification. Clients of landscaped sites want that full garden look from day one. Property owners, contractors and landscape architects achieve this by densely populating the ground with plant material, regardless of species size at maturity. It sells and leases properties, plain and simple.

But what are the long term costs? And is this sustainable? When asked to review site planting plans or conduct turnover inspections, we regularly advise clients to reduce planting density or remove plants which are already in the ground. Gasp!!!

Why?

  1. Maintenance: Costs of constantly pruning plants to contain their size at maturity is a waste of resources. Over-planted sites require multiple pruning visits each year, even forcing contractors to use the dreaded hedge trimmer where it does not belong.
Ornamental grass cut back
Miscanthus sinensis (silver grass) annual pruning Feb. 2019
Ornamental grasses
Same Miscanthus sinensis May 2019. This species at maturity is at least 3′-4′ tall and wide. A reduction in the number of plants used would not have even been noticed.

2. Water: Plants compete for water resources. An over-planted site requires more water, much of it wasted by plants blocking the sprinklers.

Sprinklers throughout this site are blocked by plant material. Note the two different sprinkler heads. Both situations lead to issues with water distribution uniformity=WASTE

3. Soil: Plant roots compete for soil space. More roots, less soil, more water use, more fertilizer use.

4. Waste: Clippings from pruned plants must be raked up, removed and hauled away, as most large landscapes do not have their own composting operation on site (we wish they did). Labor and fuel resources are wasted, even if the eventual destination is a municipal compost facility.

The long term costs for maintenance, water and waste removal get passed along to the end user – the property owner, municipality or community.

Dietes grandiflora (fortnight lily) looking normal for the species Feb. 2019. Size at maturity 3′-4′ tall and wide. There must be at least 600 of these on this site.
Same fortnight lilies after they are cut back. The landscape contractor is really left with no other option. Horticultural recommendations call for this species to be dug up and divided every 4 years or so. Not with +600 plants!

Comparison of planting densities and maintenance costs over time for the Miscanthus sinensis (silver grass) planted in late 2013

INITIAL
PLANTING		 MAINT.
FOR 10 YR		 TOTAL
AS PLANTED W/
5-GAL PLANT		 $8,750 $5,200 $13,950
40% LESS DENSITY
5-GAL PLANT		 $5,250 $3,120 $8,370
40% LESS DENSITY
1-GAL PLANT		 $2,100 $2,180 $4,280

Assumptions:

  • 250 ea. of species planted from 5-gallon stock
  • Cost per 5-gallon plant installed $35
  • Cost per 1-gallon plant installed $14
  • Time per plant to cut to the ground, clean up, and haul debris once per year: 5 minutes/5-gallon plant
  • Time per plant to cut to the ground, clean up, and haul debris once per year: 3.5 minutes/1-gallon plant
  • Maintenance labor rate per hour: $25

As you can see, costs over time for a less densely planted site using smaller container sizes saves money and resources. The costs indicated are for maintenance alone, not including water wasted, plants dying for lack of irrigation coverage or root competition, composting, etc. Many plants actually establish and grow better when a smaller container size is used at planting.

An aesthetically appealing, resource friendly landscape is within reach if we formulate planting plans and densities with species selection, growth rate and size at maturity as the main driving force. This is a more sustainable landscape approach. Properties will still sell and lease if done thoughtfully.