The parking lot project is at the Oregon Garden and was initiated with a grant from SPROUT. It was really an effort to design a planting for a parking lot that would require minimum inputs after planting, specifically water, but also fertilizer and pesticides, in particular herbicides of course, as the major pest problem in such planting is always weeds. By eliminating irrigation, you then require drought-tolerant plants capable of surviving the dry summer here in western Oregon. The climate here is a pseudo-mediterranean one with little or no rain in June-October, and fairly warm summer temperatures with 15-20 days above 30C. Our plant palette then was chosen with this in mind, and an additional requirement was that many of the plant be effective evergreen groundcovers. Over the last few years we have evaluated a number of genera of drought tolerant plants for groundcover, including Ceanothus, Cistus, Halimium, and soon Arctostaphylos and Grevillea. Out of the trials so far, we have selected a number of cultivars which can be grown without summer irrigation and which have a desirable, low, spreading growth habit which make them very effective at suppressing weeds. If we have good groundcover and if we eliminate summer irrigation, weed problems are substantially reduced. Most of these selected plants also thrive in relatively poor soils, reducing the need for fertilizer applications.

So, the basis of the project is appropriate plant selection, it is really quite simple. The term “Sustainable Parking Lot” was actually applied by the SPROUT staff, I prefer “low-input” as a description, myself. I’ve attached a couple of photos of the project so you can see the site prior to landscaping and more recent photos after planting. The site consists of two, long narrow strips which originated with the construction of the parking lot. The soils here are very full of rock-this was a problem for planting. In many situations like this, landscapers would simply drop a sandy “topsoil” typically used around here on top of this rocky soil, and plant into the sand (texturally, this “topsoil” is sand or sometimes loamy sand). We did not want to do that, as besides the rock, the soils are actually quite good quality, if the compaction resulting from construction is eliminated. The two planting strips were roughly graded, and soil samples collected for analysis, but no further work or amendment were done (again, to minimize inputs). The planting was done in May 2007. A plant list is attached. After planting, ½ of each planting strip will be irrigated, the other ½ will not be irrigated. Plant performance in each area is evaluated in late summer, to demonstrate how plant quality varies between irrigated and non-irrigated area.

I hope this answers some of your questions. If you have additional questions, please let me know.