Training Roots to go deeper - Advice Needed

We have just installed a Rachio 3 Controller and in looking to setup the zones, I have discovered that the local gardeners have (as I always suspected) been overwatering the grass. I got a resident to dig a sod and they discovered that our St. Augustine grass roots are basically only 5cm. They never gave the grass a chance for the roots to need to search for water. So I am starting off our watering with 8cm root depth.

Is 8cm an appropriate starting depth ?

How often should I increase the depth increments ?

By how much should I increase the increments by ?

Sources I’ve read say that St. Augustine should have roots at least 6" (15 cm) deep. And that (surprise) “Over-watering and watering shallowly contribute to poor shallow root systems.” A surprising number of people (even here) just don’t believe the soil should be allowed to dry out some before watering again.

Anyhow, if your roots are only 5 cm deep, then starting with 8 cm wouldn’t be too bad, or even 10. Some roots get so think and spidery, it’s hard to tell. You certainly wouldn’t want to go immediately to 15 cm, but should work your way up to it, probably over a season or so. Realize this will mean watering more time, but less often, which is what is best.

1 Like

Many thanks,

I got someone to dig down and the soil was wet to a 6 inch depth, which is great news knowing that our clay soil is holding water.

For years, our gardener has been watering the grass for 20mins every second day, at considerable expense. The Rachio unit, in our case, will now possibly pay for itself in a week !!!

2 Likes

To develop deep roots, you need to water deeply and less frequently. Try once a week. Low tech method is to dig down 6 " to see how deeply the water has permeated to 4-6" depending on your soil type. That will tell you how long to irrigate.

Controller method in the ADVANCED section: Set the root depth for your grass at 4-6". St. Augustine is a warm season grass. Enter the precipitation rate of your irrigation Spray or Drip, inches per hour, in the Rachio. Also set slope, light conditions, etc. Set it on a fixed schedule, once a week. Watch it to see if it is getting deep water and how the grass does. Yes, the soil should dry out in between watering because plants need oxygen to enter the soil where the water was. They rot with out oxygen.

1 Like

Thanks for that.

By what increments and what frequency of increments would you suggest, the bring the grass from 1.5" roots to 6" roots please ?

It isn’t an exact science. You’ll have to monitor the grass as you make changes, and adjust according to how it reacts. In the summer months you may see some dry spots as you work thru this.

If the grass is even remotely established, regardless of whether it was watered “incorrectly”, I would start deeper than 1.5". I’d say 3" is a good starting point.