Martha Retallick's Monthly Newsletter | October 14, 2025

Here Comes the Rain!

After a yearlong drought, there’s nothing like good, thumping thunderstorms with plenty of rain. More than an inch, in fact!

We in Tucson would like to thank the remnants of Hurricane Priscilla and Tropical Storm Raymond for being so generous.

I'm especially grateful because Priscilla and Raymond have filled my 1,500-gallon cistern to capacity...

Now, as a water harvester, what’s the most important thing to remember when you’re designing your systems? Four words:

Always Plan for Overflow

Take, for example, the rainwater harvesting basin shown at the top of this issue. It’s harvesting water from 500 square feet of roof.

That water leaves the roof via rain gutters that connect to a downspout at the southeast corner of my house:

After the water exits the downspout, it flows downhill via a drainage swale and ends up in the basin.

Mathematical Moment

I’ve already mentioned 500 square feet of roof. Here are more units of measure:

During a one-inch rainstorm, the aforementioned basin will collect 250 gallons of rain, which is its capacity.

But we know how rainstorms can be. It’s not like we can arrive at the one-inch mark and say, “Thanks! We’re good!”

That rain will keep on falling for as long as it’s going to fall.

How to handle that basin overflow?

Connect it to a secondary basin! Here are my two rainwater harvesting basins -- before Priscilla and Raymond came to town:

In my front yard, the primary basin (background) collects rainwater from the roof. The secondary basin (foreground) handles overflow.

In the five years since these basins were installed, I have yet to see any overflow into the secondary basin. Oh, well.

But how about some flow into the primary rainwater harvesting basin, framed by mesquite tree branches?

Q: What happens when my cistern fills up? Where does the excess water go?

A: Into the overflow basin in my backyard.

Overflow in a Greywater Harvesting System

In addition to my rainwater harvesting, I recycle my “used” wash water via a laundry-to-landscape greywater harvesting system. It irrigates my lemon, fig, and pomegranate trees.

Here’s the thing about any irrigation system: Emitters can get clogged.

If there’s a washing machine at the other end of that irrigation system, you don’t want trapped greywater to come blasting back into your house.

Here's what greywater overflow looks like:

Not to worry, my emitters didn't get clogged. I just shut them off to take the photo.

Tip: This photo is included in my coffee table book, City Nature. And, just in time for the holidays, quantity discounts are available.

Kirkus Reviews calls City Nature “A beguiling ramble full of captivatingDIY information and arresting visuals of flora and fauna.” ​ Buy now

Fall Colors

In the Southwestern deserts, we don’t experience fall colors like, say, the Northeast and Midwest. But we do get to enjoy changes like these…

The cactus lives off of rainwater, and, for the most part, so does the Texas ranger.

However, during droughts like the one we're emerging from, I give the Texas ranger an occasional splash of greywater with my dish washing pail.

Our Prime Gardening Season

Unlike the northern climes, our prime gardening season is during the fall and winter months. I’m pleased to report that my malabar spinach is right in tune with the season…

In last month’s issue, I mentioned the nitrogen-fixing cover crop I had started in my raised garden beds.

How are those tepary bean plants doing? Just great!

Before we leave the garden, here’s a preview of what’s to come...

Save the Date

I'll be speaking at the Tucson Organic Gardeners Fall Garden Fair on Saturday, October 25.

The fair will be hosted by the Arizona State Schools for the Deaf and Blind, 1200 West Speedway Boulevard in Tucson.

Topic: Growing Food with Water Harvesting

Time: 9:00 am - 10:00 am

Location: My presentation will be in the recreation room adjacent to the outside fair area.

There is no charge to attend my presentation or the fair.

Bonus Birds of the Month

My yard continues to be quite the birding hotspot. Here are my favorite recent visitors.

Questions? Comments? Hit reply and let's talk! I'm looking forward to hearing from you.

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