Saturday, January 17, 2015

Nut Trees for a Mediterranean Climate

In another post, we discussed good fruit trees for those lucky enough to live in a Mediterranean climate.  Here we will discuss the best nut trees for the same climate.

The Mediterranean climate, also known as a dry summer subtropical climate, is characterized by warm summers and mild, wet winters, with temperatures rarely dipping below freezing.  Only a few portions of the world outside the Mediterranean basin have this climate, including parts of South Africa, Chile, Australia, and southern California here in the U.S.

From Wikipedia
The Mediterranean climate can be wonderful for those wishing to grow fruits and nuts due to its mild winters.  However, the lack of summer rain can make establishing trees very difficult - that was until the advent of the Groasis Waterboxx - a self refilling water battery for trees that slowly irrigates the roots of the young plant.

What nut trees grow best in a Mediterranean climate?  There are several, including many that are popular in the U.S.

This wonder food, Carya illinoinesensis is probably best known as a pie topping, but if eating this nut alone it is remarkably healthy.  Pecans are very difficult to establish because they have a true, deep taproot that means their roots need to be constantly wet when planting - a job perfect for the Waterboxx.  It is important to get pecans suited to your area (see here for California).  The pecan is originally from the Mississippi Valley, so it does require water during the summer months.

Carya illinoinensis.jpg
Pecan, grown for shade - From Wikipedia, By Bruce Marlin [CC BY 3.0 (], via Wikimedia Commons

Walnut, or Juglans species, are very interesting trees.  Renowned for the quality of their wood, their nuts are also highly desired.  Walnut roots produce a chemical called juglone which prevents growth of nearby plants so any walnut groves need to be isolated from other plants and trees.  Although walnuts are monoecious (both male and female flowers on one tree) you need more than one for proper pollination due to differences in timing between shedding of male pollen and receptivity of female flowers (in other words, they are called dichogamus).  Walnuts need well drained soil.

These can be somewhat difficult to bring to full production because they do need watering during the summer nut ripening period.  Also, it is very important to properly process and store the nuts because a cancer causing chemical called aflatoxin can be produced by a fungus on improperly stored shells (as it is produced in many other plants under improper conditions).  These trees are also slow growing - taking a minimum of 5 years after planting grafted trees to get any nuts.  If you are patient and in for a challenge with a great reward, pistachio may be for you.  You will need one male tree for every 9 female trees.  Male trees do not produce the nuts.  Here is a list of nurseries where you can buy pistachio trees.  Planting with the Waterboxx can give the roots more consistent water and better growth early in the tree's life, potentially decreasing time to nut production.

Ripening Pistachio Nuts - From Wikipedia, By Paolo Galli (Own work) [CC BY-SA 3.0 (], via Wikimedia Commons

Prunus dulcis, almonds are actually a stone fruit that is treated like a nut.  These trees are superbly suited to a Mediterranean climate, and in the U.S. grow best in southern California.  They bloom in February, and need consistent watering after planting, best provided by the Waterboxx. Of note, it is very important to never eat wild almonds as they contains the chemical amydalin which can be converted into hydrogen cyanide, a very deadly poison.

Castanea species, these are the only nut that contain vitamin C.  These trees can be harvested in October.  Chestnuts are very drought resistant once established, and the Groasis Waterboxx is the perfect device to establish deep roots without continued watering.  These trees prefer a soil pH of 4.5-6.5.  You will need at least two chestnut trees to have production of nuts.  More detailed instructions on planting chestnuts can be found here.  Chestnuts are generally cooked in aluminum foil until one pops - then the rest are eaten.  Without cooking they can be quite bitter.

Planting nut trees with the Groasis Waterboxx
Areas with Mediterranean climate can be wonderful places to live, garden, and grow trees - if the trees can get deep roots established.  The Groasis Waterboxx solves this problem, and ends the need for irrigation of young trees, by slowly releasing stored water to the roots of the growing tree.  The water is also prevented from evaporation by the Waterboxx, meaning a column of water will grow directly beneath the tree, inducing the tap root to grow straight down to deeper capillary water.  The Waterboxx refills itself from rare rain and morning dew, funneling it into a reservoir for later use.  The Waterboxx is explained in the video below:

The Waterboxx can be reused for up to 10 years, and used for planting multiple different trees.  The Groasis Waterboxx can also be used for growing annual garden plants.  The Waterboxx can be purchased from Dew Harvest here.

Harvesting and Storage
As mentioned above, improper harvesting and storage of some nuts can lead to contamination with aflatoxin, which is potentially lethal due to liver damage and cancer causing properties.  The University of California has an excellent resource on how to harvest and store many of the nuts discussed above.

Try Out The Waterboxx
The Groasis Waterboxx is available for purchase from Dew Harvest in the United States.

If you would like to learn how to grow plants without watering with the Waterboxx, the best resource is the book The Waterboxx Gardener: How to Mimic Nature, Stop Watering, and Start Enjoying Your Garden available here on 


  1. This seems like a great and potentially very useful product and it would be very interesting to test drive, however the cost is prohibitive and impractical for anyone interested in planting a significant number of trees on a large scale. How could this product be designed / manufactured so as to be more within monetary reach? At your discount prices to buy 50 of these would cost 30 dollars per waterboxx. That is likely many times more then the investment in the actual individual tree itself.

  2. Your blog is awesome. You have shared very valuable information to us. Thank you so much for sharing this.

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