How to chose the right Eucalyptus for your landscape

Windmill Outback Nursery

With almost 1,000 different Eucalyptus (Angophora, Corymbia and Eucalyptus) species to sort through, how do you find one that might work for your landscape?  (In this article I will refer to all as being "Eucalyptus".

A simple process using some detective work is the first place to start.  While I don't intend this to be a college course on horticulture for you to sort through, you should be able to run down the checklist and come up with solutions.

Ready - Let's look at your environment!                       

Sun or shade: Eucalyptus prefer full sun, some like E. neglecta or E. camphora will do OK in dappled shade.  Overall, the more sun the better!  Best growth rates are obtained in full sun and growth rates diminish with an increase in shade. 

Soil: Soil is the anchor for your tree.  Nutrients for plant growth are derived within the soil as well as being a source for moisture for continued growth.  What type of soil do you have?  While most  Eucalyptus species prefer a well drained soil, the soil type must be understood.  In this discussion, soil types are:

    Sandy: Soil is very loose, granular, much like what you would find along ocean beaches.  It drains freely, but holds very little nutrients for plant growth.  Sand feels gritty to the touch, like coarse sandpaper.

    Sandy loam: Soil texture is somewhat loose, but not as free as sand.  It contains small particles of sand as well as other organic particles.  It can hold nutrients for plant growth as well as providing soil moisture.  Drainage is usually good.

    Loam: Similar to sandy loam, without the sand.  Usually holds nutrients and provides adequate pore space between soil particles.  May tend to need additional watering (depending upon plant species.)

    Gravel soils: Contains parts of sand, organic matter and of course, various sizes of gravel.  May include some clay soil as well.  As easy way to ID this is to look at a stream bank.  Normally, just above the water line, you will see gravel that is packed in with other soil particles that filter downwards.

    Clay: Feels smooth to the touch, slick feeling.  Pore space is minimum and it tends to hold nutrients and moisture.  Drainage is essentially poor, although clay does provide a good "anchor" for some plants.  It has a tendency to compact when wet and is difficult to work and dig in.

    Clay loam: A mixture between clay and loam particles.  Drainage is still poor, although not as bad as clay.

    Sandy clay: A mixture of both sand and clay, very difficult to work with and little drainage.  Adding sand to clay forms bricks.

Soil pH - how it affects your plants: pH is a measurement of the acidity or alkalinity of your soil. It is determined by the amount of lime (calcium) contained in your soil, and the type of soil you have.  Why is this important?  Nutrients (fertilizers) for plant growth are "bonded" within the media (soil). In the case of Eucalyptus, they prefer an acid pH of 5.5 to 6.4.  If your media (soil) pH goes above 7.0, nutrients like iron are "locked up" and are not available for plant growth.  Spraying chelated iron will not correct this if the pH is not correct.  If you see yellowing leaves where the leaf veins remain green, suspect improper pH first.    

Example of iron deficiency - leaves turn yellow and leaf veins are green.

Does this mean your soil is iron deficient?  Not necessarily so.  If your soil pH is too high, the iron may be locked up and not available to the plant.  You can test your soil pH with a simple pH tester found at many garden supply stores.  They are relative inexpensive (usually less than $10) and a good investment for quick test.  Simply insert the probe into the media and in 10 seconds it gives you the pH reading.  Again, Eucalyptus prefer the acid range, 5.5 to 6.4.

A bit further into understanding nutrients:

Notes on the above diagram: As soil pH decreases, the amount of nitrogen and phosphorus decreases.  Note when pH of about 6.0, iron becomes less available as the pH rises.  Again, early warning signs of high pH in your soil is when you notice yellowing of the leaves.  Eucalyptus do not need excessive fertilizers as it only leads to soft, easily damaged new growth.  In fact, I never fertilize Eucalyptus that are planted into the landscape.  If your soil pH is in the 5.5 to 6.4 range, Eucalyptus can extract the proper nutrients from most soils.  If your soil pH is not right, no amount of fertilizer will correct the pH imbalance.  Continued use of fertilizers only leads to a waste of your money and leaching runoff of nutrients into the groundwater.

What do I do if my soil pH shows too high? How can I correct this?  For long term, addition of peat, compost or manure will be helpful.  To reduce the pH by 1.0 unit, thoroughly blend in any of the following: 1)Peat moss, 2.5 pounds per square yard, or 2) Compost at 14 pounds per square yard, or 3) manure at 5 pounds per square yard.    For short term fixes, powdered sulphur can be added by top dressing or mixing into the soil at a rate of 1.2 ounces per square yard on sandy soils or 3.6 ounces on other soil types.  For an even quicker "temporary" fix, I have used household vinegar at the rate of 1-2 teaspoons per gallon of water.  I used a Ortho brand hose end sprayer where you can adjust the dosage rate to what you need.

OK - enough about soils - if you got through the top part, the rest should be a breeze for you!

WATER - you can't live without it!        

    Eucalyptus are found distributed throughout all of Australia and Tasmania.  Australia soils are very well drained and most often very shallow in depth (over bedrock of sandstone or granite.)  They are also lacking in many nutrients (hence the need to NOT fertilize Eucalyptus!)

    Average climate data for rainfall ranges from just a few inches per year, upwards of 100 inches or more.  Think desert climate vs tropical rainforest.  Obviously plants in a desert environment have adapted to low water needs and tropical rainforest plants need the humidity and moisture to survive.

    Somewhere in-between the high and low rainfall, Eucalyptus can be found.  Eucalyptus striaticalyx does quite nicely with just 150 mm (about 6" of rainfall) per year, where Corymbia gummifera needs 27-70 inches of rainfall per year.

    An easy way for you to identify your "normal" annual rainfall data is to contact your local agricultural extension agent or do some web searches for specific climate data for your area.  Obviously, if you are trying to grow a rainforest type Eucalyptus in a desert climate, additional watering will be needed and your chance for plant success will be less.  On the other hand, if you are trying to grow a desert Eucalyptus species in a tropical rainforest you will again run into problems.

To select the best Eucalyptus species for your climate, start with those with similar moisture needs for your area!

Frost Tolerance: Some species may be listed as "frost tolerant".  This means they are "tolerant" to occasional frost, not long-term freezing temperatures, ice storms and snow!  The greater degree of cold, the more damage that will occur.

Heat: What we need in winter! 

In all my years of growing Eucalyptus, I have never seen too much heat in my climate zone to be a problem.  Winter wet - yes, but heat, no!  With that being said, of course "Snow Gums" are not going to grow well in a desert climate, nor will they survive saturated winter wet conditions even though they are found along snow lines in Australia.  (Drainage is the key!)  Of course, there is the occasional problem of "sun-scorch" where you have elevated temperatures and a lack of rainfall for the species you are growing.

Even so, our Eucalyptus Zone ratings are rated based entirely upon COLD, how cold does it get in your climate?  You can search a USDA Climate Zone map for cold hardiness zones.  Some web sites offer USDA zone information based upon your zip code, Arborday.org  is one such site.  Simply type in your zip code and your zone is displayed.  Sorry, the National Arbor Day Foundation does not list Eucalyptus as it is not a "native" species of American trees.

Ok - ENOUGH OF THIS you say!  Tell me how to select the best species for my area!

I put together a chart where you can fill in your data based upon your climate and soils.  Print out the chart, fill in the areas that pertain to you and keep on hand for reference.  As you browse through our site, use your chart to get you started in the selection process.  Of course, the more details you provide in your chart, the better the selection process will go.  Don't try to skimp when filling in the chart, if you don't know something, do some investigative work to find out.  I can't tell you all the details about your climate, you live there and have far better access to that data then I do.  I'm certainly here to assist you with plant selection, I just ask that you have sufficient background climate and soil information if you want my professional opinion.  My suggestions can only be as good as the details you provide!

Click here   for Selection Chart

One final note, Eucalyptus range in mature size from a few feet, upwards to several hundred feet!  Obviously you don't want a 200' tall tree next to your house.  Always consider the "ultimate" size before planting into the landscape.  I get emails almost every week asking me how they can move their Eucalyptus that they planted next to the house and it grew and grew.  A little bit of thought beforehand goes a long way.

Did you find this information helpful?  Did we leave out information that you needed?  A brief note to us will help me identify your needs.  Simply send an email to australiaplants@nexet.net with you comments would be appreciated!

 

Copyright Windmill Outback Nursery. All rights reserved.

Sunday August 28, 2011 07:33 AM

australiaplants@nexet.net