Question
Hello, I was wondering if you could offer up your recommendation for a soil recipe for planting Crepe Myrtles and one for perennials if much different.

Thanks.

Answer
Crape Myrtle asks little considering the flourish of flowers it unfolds.  The University of Georgia College of Agricultural and Environmental Sciences Extension has collected its findings on these landscape plants and posted them on its website:

http://pubs.caes.uga.edu/caespubs/pubcd/L331.htm

Read what they say about preplanting preparations:

'Research has shown that organic matter amendments are not necessary when planting in individual holes. Amendments in the hole encourage roots to stay within the hole and not grow outward into the surrounding native soil. Amendments are most beneficial, therefore, when they are incorporated uniformly throughout the soil surrounding the planting hole.'

This sounds to me like conflicting messages.  On the one hand they say that surrounding the rootball with rich soil is 'not necessary', then in the same breath they suggest it is counterproductive because roots grow around the plant instead of spreading out, then they come right out and say that deep, rich soil in the vicinity of the plant is best.  I don't know if these people are running for office or what, but they should just come out and say it.  So let me translate here:  The right way to plant a Crape Myrtle is to surround it with rich organically fortified soil, several feet beyond the rootball; if you limit the rich soil to the planting hole, the roots will say compact and the plant will never reach its full potential.  Sort of like limiting a child to Baby Food for the first 21 years of its life.

Sure, you'll find people who tell you their Crape Myrtle is 'fine' with a basic hole.  Either they don't know anything about the surrounding soil and it happens to be very rich, or they are so clueless they don't know what rich soil is and it looks good to them so it's 'fine'.

In 2 years, it probably won't matter much.  In 10 years, a skillfully planted Crape Myrtle will reflect the sweat that went into soil amendments when it first went in the ground.

So the 'recipe' here is LOTS of rich, organic matter.  Leafmould, Humus, Compost, soil that is teeming with microorganisms and Earthworms, generating a balance of nutrients at just the right speed.  Microbes are better than a bag of Scotts any day.  Microbes work according to the temperature, the water, the season.  Scotts just dissolves and washes past the roots; some of it goes in, most of it washes away, stinging the microbes it washes over with its hostile Salt particles.

Not to restate the obvious, but the difference between the Myrtle and the perennials is that the Myrtle has a huge root system, and perennials have a comparatively modest root system.  Myrtles and Perennials will both live longer and better in rich, organic soil.  But the Perennials are much more shallow.  Less work.

You're probably wondering about pH of the soil around this Myrtle and those perennials.  Including Peat Moss in the Planting area will contribute to slightly more acidic pH readings and make the plant happy.  Toss your leftover Orange Juice, used Coffee Grounds and black Coffee (NOT with Cream or Milk!), fruit peels and rinds, etc, around the Myrtle after it's planted to help the pH adjust.  Fact is, the microbes in the Soil will work with the exudates from the Myrtle roots -- we did not know these things a few years ago.  Rich Soil, built from the ground up of natural organic matter and a bag or two of Peat Moss, will contain its own populations of Bacteria and Fungi that will respond to the Crape Myrtle as it signals for just the right pH it needs to be happy.

Perennials as a group fare best -- generally speaking -- when grown in slightly Alkaline soil, with a few exceptions.

Enjoy your Crape Myrtle planting project.  Any more questions, please ask!