Kate Coulson garden, late summer, South of France

Over the last couple of years, I have been researching plants that make beautiful gardens  and can survive and thrive without irrigation in our Bay Area climates. I was introduced to  the idea by garden makers in New Zealand (Jo Wakelin) and France (Kate Coulson) who  share information online about plants they use to create what their stunning “dry gardens”.  Kate Coulson’s house is in a dry mediterranean climate in the south of France. Jo Wakelin  lives in a semi desert climate on the South Island of New Zealand.  

Here in the Bay, we receive more rainfall than both these areas and in the case of central  South New Zealand, we receive double. So, I began to ask myself: why do we begin building gardens with the premise that we have to first install an irrigation system? Why can we not  live within our means and just accept the water that comes? 

I set oP to find out how a ‘natural rain garden’ here might work here. I have taken to using  the term ‘natural rain garden’ because I want to emphasize the naturally available rain in  the winter rather than the lack of it in the summer. In a dry climate, the idea of a “dry garden” doesn’t have much appeal, instead conjuring up images of dying plants, or desert  plants like cacti.

Robin White, 1 year old natural rain garden, Oakland

The truth is the contrary. A rich collection of plants from all over the world do well for us  with no additional water, including some surprising standards such as roses and bearded  irises. My search has led me to some rare beauties - stunning sinningia ‘invasion force’ and  dicliptera squarrosa, for example. The curious rock samphire, crythmum maritimum,  shown in the foreground above was a food source in Shakespeare’s time and grows in the  wild from the shores of Great Britain to the shores of the Mediterranean.

Sinningia ‘invasion force’, RW garden, Oakland

Dicliptera squarrosa, RW garden, Oakland

These plants have interesting methods of keeping themselves hydrated during our dry  summers. Roses have very long roots that draw up hidden water from underground.  Sinningia, from Brazil, has large tubers that expand in the rainy season to hold reserve  supplies. Crithmum maritmum looks a bit like Queen Anne’s Lace. and is related to it, but  this plant is a succulent storing water in fleshly grey green leaves. Irises from Europe and  Asia have rhizomes that hold water and thick waxy leaves that reduce evapotranspiration.

Iris palida, RW garden, Oakland

Crithmum maritimum, RW garden, Oakland

It was clear early on that California natives would play a big part in this project although there is a common myth that “California natives do better with some water”. I suspect the irrigation industry promulgated this bit of nonsense. The truth is much more nuanced.

I was once involved in the overwatering death of a lovely specimen of arctostaphylos ‘howard mcminn’, a plant reputed to be “tolerant of garden watering”. The natives I have in my own garden, such as eriogonum giganteum and arctostaphylos ‘pacific mist, do fine without summer water although some natives need it for establishment. It varies.

Arctostaphylos ‘pacific mist’ RW garden, Oakland

I began to build lists of plants that might work based on observation or research. I started  noticing gardens that obviously were getting no water and made notes of which plants were  thriving in the drought. I had often noticed roses blooming in abandoned gardens, for  example. I came up with a rule, which was that to be accepted onto my lists I either had to  have seen it with my own eyes, grown it myself, or be absolutely certain of the evidence  that it would survive the rigors of a dry summer. I scoured Jo Wakelin (@jo.wakelin) and  Kate Coulson’s (@katecoulson) plants on Instagram, and got clues from the Mediterranean  Garden Society (@mediterranean.garden.society), Saxon Holt’s Summer Dry Gardens (@summerdry.gardens) project, Panayoti Kelaidis(@panayotikelaidis) in Greece, Gundula  Anders (@giardino_di_hera) in Southern Italy and others. 

Along the way I also gathered information about how to build such gardens successfully.  

Firstly, it’s critical to use a deep (6”) layer of gravel or pebble mulch. Plants love it. Wood  mulches dry the soil out. Wood is full of capillaries that suck up moisture and evaporate it  into the air, but gravel stays cool in the shaded lower layers and has the potential for  condensation underneath as moisture moves up through the soil and meets the cool rock  above.  

Second, plant with the rainy season if you can. The earlier in fall and winter, the better.  

Third, allow for an establishment period of a year or even two. Make sure the garden is  watched and hand watered about once a month in the first one or two summers if it needs  it. Learn to read the plants. Not all need the same thing. 

Fourth, if you can, use deep rooted plants if they are available. This is one time when it may  be better to start with bigger sized pots from the beginning. The plant roots will begin  deeper down in the ground, closer to hidden layers of soil moisture. Make large holes and  spread the roots out when you put them in the ground. Water them in well. 

Fifth, adjust your expectations. For some plants in a natural rain garden, the height of  summer is a period of ‘estivation’, or summer dormancy. Some plants might lose leaves or  die back in this period. If you carefully watch our native evergreen trees such as oaks and  redwoods, they drop leaves and needles in the summer. Learn to embrace the brown that  goes along with the end of summer period. 

Eriogonum giganteum fall color, RW garden

End of summer colors in Bill Milligan’s garden in Blackhawk

Sixth and finally, you need to plan for the “care gap”. With an ordinary irrigated garden, a  landscaping company such as ours can install the plants, set the irrigation controller and  walk away. Set and forget.  

With a natural rain garden, it is important for someone, ideally with experience, to be  watching the garden in the first year or two to make sure that young plants have a chance to  establish themselves with deep root systems before they are expected to go it alone  without irrigation. We can provide that service also.  

Kate Coulson recommends hand watering (I would suggest with an oscillating sprinkler) once a month in the first summer. In my garden in Oakland, my own experience was that  many plants, put in the ground by September, had established their root systems enough to  survive the following summer without further watering. Plants put in the ground late in the  rainy season needed much more careful attention. It also varies to a certain extent with  aspect, the amount of sun or shade that plants receive, and with location.  

To sum up, there is a lot of potential to build successful and beautiful gardens in the Bay  Area without using irrigation. Using techniques developed by gardeners in dry climates  around the world, using plants that grow in dry places from around the world, and by  adapting our expectations of what a garden looks like and how it should be made, we can  make gardens that are both interesting year-round and that in the end save money, time  and resources. (Scroll down for more images). 

Susan Boyle garden, Oakland, establishment phase 

Susan Boyle garden, Oakland oxalis incarnata happy in dry shade

Susan Boyle garden, Oakland, carex divulsa in shade

Arrtemesia ‘canyon gray’, late summer, Bill Milligan, Blackhawk

Eleagnus ‘gilt edge’ in deep, dry shade, Julia Partridge, Oakland