Planting Design for Dry Gardens

Design ideas

Book Review: Planting Design for Dry Gardens by Olivier Filippi

With summer slowing down I have been gazing longingly at my yard. When I saw this book at the library, I grabbed it and have enjoyed browsing through it.

Planting_Design_for_Dry_Gardens_bookbyOlivierFilippi

Image from Amazon

This book has amazing photos. I love being able to see what he describes. Mr Filippi has a fascinating introduction that talks about how lawns came to be so incredibly popular and why it is time to explore some landscaping alternatives. He then describes a variety of groundcover options that encompass everything from lawns and meadows to gravelled areas and shrubs. I love how he states the advantages and disadvantages of each landscape. Here are his categories:

  • Lawns with warm-season groundcovers
  • Green carpets: plants you can walk on
  • Flowering carpets: a mixture of groundcover plants
  • Mixed grassland “lawns”: the art of cultivating weeds
  • Flowering steppes
  • Gravel gardens
  • Terraces, paths, and steps: the greening of stone surfaces
  • Perennial and shrub groundcovers for large areas
  • Pioneer plants for slopes and wild gardens
  • Flowering meadows in dry climates

The best part about this book is the step-by-step instructions for executing the design. The second section of the books describes how to prepare and plant each type of groundcover. I didn’t know that heavy clay soil has to be “decompacted” in order for most plants to establish well. You must break up the clay so that roots can spread throughout the soil. He recommends digging to a depth of 30 cm, but I don’t think I am strong enough to dig Arizona soil that far. :/  I also learned that a gravel mulch 6 cm deep is thick enough to suppress germination of most weeds. The hands-on landscaping expertise makes this book a valuable resource.

I like how Mr Filippi encourages us to embrace plants in all seasons and plan for summer dormancy in dry areas. A summer dormant landscape in Arizona conserves water and requires less care when it is least comfortable to be outside.

demonstrationgarden_spring

Demonstration garden in spring

demonstrationgarden_summer

Same demonstration garden in summer. Images from mediterraneangardensociety.org.

This book has a disadvantage of using plants for European landscapes. While some of the plants may be available here, the goal of xeriscaping ideally uses plants from the same region that are most ideally situated for the climate. The concepts in this book can easily be transferred to a palette of southwestern plants.

 

If you like reading landscaping books, I definitely recommend this one.

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How to water desert trees

Plants

Desert trees anchor a xeriscape. Such important plants need proper care to look natural and avoid damage. Amazingly one of the best things you can do for a desert tree is NOT water it all the time. Over watering encourages fast, weak growth. When summer windstorms come, a spindly tree loses main branches, potentially ruining its form. My neighbor had an entire tree disappear in a windstorm!

Severely_pruned_mesquite

This Mesquite is nearly full grown, yet has been severely pruned to prevent damage from wind. Watering less frequently would give a better natural form without the need for pruning.

When I plant a young desert tree, I build a basin with edges about 2 feet away from the tree’s trunk. I’ll start by watering the tree every few days for the first week or two while it recovers from transplant shock, then I fill the basin once a week while the tree gets established, about the first year. After a year, a desert tree can live with watering once every 2 to 4 weeks. If the tree seems to be growing slowly, you can increase the water frequency to no more than once per week.

Baby Palo Verde basin

A lush baby Palo Verde tree with a 2 foot basin.

As the tree grows, expand its basin. Once a year in spring you can rebuild the sides of the basin farther away from the trunk. The basin around the tree allows you to give a large drink with each watering, penetrating farther into the soil and allowing the trees roots to grow deeper. Shallow watering encourages shallow roots, which allows the top of the tree to become heavier than the root strength. In order to allow the basin to fully fill, turn a hose on at a trickle and set a timer for an hour, monitoring to make sure your basin doesn’t overflow. Or if your tree is on your irrigation system, you can add the number and flow rate of emitters needed to fill the basin in the time scheduled for your system.

Desert_tree_basin

A larger basin on a more mature desert tree. This basin measures about six feet across and is doughnut-shaped to encourage roots to spread away from the trunk. This tree blew over a few times while young and needed stronger roots.

Once my desert trees have doubled in size or seem well established, they can be watered even less frequently. A few of my trees border a low spot in my yard where water pools when it rains. These trees are not on my irrigation system and I hardly ever water them by hand. The winter and summer rains give them deep drinks which keep them healthy. They usually keep their leaves all season long, so I know they are getting enough water.

Juvenile_Palo_verde

This Foothills Palo Verde has been in the ground about 5 years and no longer needs any irrigation since it borders a low spot in the yard.

When watered appropriately, desert trees grow slower with more proportional shape and stronger branches. Over time they can still grow to mature heights of up to 30 feet, and much more quickly than they would in the desert.

Ironwood leaves die in spring?

Plants

This spring, all four of my young ironwood trees lost their leaves. The leaves turned yellow just as spring growth happened all around them. I thought somehow my trees were dying, though I didn’t see any reason why. About a month after the leaves started dying, I saw new growth. All four trees have now grown new foliage.

While I’m not sure why this happened, I’m glad the trees are still healthy. I found this information at desertmuseum.org:
“Branches that produce flowers often drop their leaves during bud formation, and re-leaf when summer rains begin”

My young trees have never flowered, but perhaps their leaves had remained on the tree long enough to need to be replaced. Ironwoods remain my favorite desert tree due to their size, leaf color, wildlife habitat, and shade. Some day I hope to have a large wildflower area with three mature ironwood trees as the backbone. I’m glad these trees are okay. They grow slowly and would be hard to replace.

Design a garden that doesn’t need an irrigation system

Plant selection

It sounds like a challenge from a reality show: design a desert garden that can survive without irrigation. Obviously you need to use low-water plants. (Native plants make sense.) Utilize the runoff from your roof to provide water for your desert garden. You can sculpt berms and basins to guide the flow of water around your planting area. Plant in fall or winter to give everything a chance to get established before the heat hits. The first year or two you can water by hand with a hose to supplement the rain. My yard has areas on a drip system and areas off–it is interesting to experiment and see how the plants fare (once you are confident enough that you won’t kill them!).

Here are some plant choices suggested by Scott Calhoun:

Next to a basin

Trees

Ironwood, Western Soapberry, Desert Hackberry. I would add Foothills Palo Verde.

Shrubs

Baja fairy duster and pink fairy duster, Bee bush, Chiltepin, Desert honeysuckle, Desert lavender, Globemallow, Southwest coral bean

Other plants

Desert milkweed, Prairie zinnia, Sundrops, Trixis

Almost all cacti and agaves do well above a basin where their roots won’t ever sit in the water.

In a basin

Trees

Desert willow, Velvet mesquite

Shrubs

Apache plume, Arizona wild cotton, Limber bush, Mariola, Oreganillo, Wolfberry, Shrubby senna, Tarbush, Yellow bells

Other plants

Deer grass, Flattop buckwheat, Goodding’s verbenia, Penstemon, Sacred datura, Wright’s goldenrod.