Are Your Dahlias Thirsty?

Dahlia Omega

Are your dahlias thirsty? I know mine have been- we went over a month June/early July in 95+ temperatures and hardly any rain. We were lucky to get a few showers in that time, I know some farmer friends who didn’t get anything.

So what did we do to keep our dahlias happy without breaking the bank?

For the past 2 years I’ve been using a system called “pulse watering”. This is a process I first heard about 2 years ago on a podcast that I love. I was listening to the No-Till Flowers podcast by Jennie Love (of Love’n Fresh Flowers in PA). She was interviewing a farmer from Tasmania and you know Australians know how to deal with all kinds of crazy weather! It’s episode 25 from season 3 if you are interested.

So what is pulse watering? It’s where you set your irrigation system up to water in short bursts multiple times per day instead of one long period daily or every few days.

The technique was originally used on sandy soil from what I can tell but I’ve adapted it for use in my clay soil. You’ll need an irrigation timer with the ability to water in multiple bursts and the ability to set it for unique timing. I’ve been using a Hunter Technologies system for years. The specific system I use is called Hydrawise. I have a 12 channel controller for my farm (that we have yet to max out). My farm is divided into 7 zones. Each zone is multiple beds. I determined the size of each zone by the area (for example: a whole hoop house is one zone) and the total feet of drip tape in that area. According to the gallons per hour your water source (well, city water, etc) will give you- this determines how many feet of drip tape you can run at one time.

So with my controller, I can set a zone to run multiple times a day for shorter time spans. It took me about 2 weeks to determine how long each burst should be and how many bursts per day. I originally trialed this in a hoop house so I wouldn’t have rain interference and could see how it actually worked. I almost flooded the hoop house on the first run! I had it set for way too many bursts per day. I would start with 4-5 and around 5-10 minutes. I find the length varies by field position. For example, my lower field has a slope to it (6’ drop) so I have to run it longer because the irrigation fills from the bottom first and can take up to 5 minutes before it reaches the top. So if I want at least 5 minutes of run time, I need to run my burst for 10 minutes to make sure each bed gets at least 5 minutes. (Yes, this means the lower beds always get more water which I take into account when deciding what to plant there.)

So why use this method over the tried and true- water deeply less often method? Well first off- that wasn’t working. In the extreme heat of our summers these days, the beds needed more water. I was finding that my beds were dry by early afternoon - the hottest part of the day. I was having to supplement with overhead watering which is not very water wise efficient. Pulse watering will actually use less water once you get it started. When you begin, it doesn’t look like it works because you only see a small circle of water. But over time, the water begins to spread out (this is especially helpful in sandy soils where water goes straight down.) Essentially, your bed never completely dries out. If you begin the process a day or two after a heavy rain, you’ll see the effects faster. Starting from a dry soil takes longer but will work just as well.

The addition of the straw mulch we began using last year completed the process. The mulch keeps the moisture in the soil and makes pulse watering even more efficient. Having clay soil helps too- it holds water better than sandy soil (especially if you’ve been working on increasing your organic matter.)

I’m not sure if I’ve explained this super well (but go listen to that podcast for more in-depth explanation)- however, it’s been a life-saver for my dahlias. The mid day drooping that is pretty normal for hot climates is not near as substantial, some varieties don’t droop at all.

There are faucet timers that will do this- you don’t have to have a full on system like I have. Although if you run a commercial operation, I highly recommend it. (I can control this system anywhere in the world b/c it’s hooked to the internet.) But for a home garden setting, you need a timer that will allow you to water in at least 5 minute increments. I’ve found Orbitz brand is great (but don’t let them freeze in the winter). When you begin, you will probably have longer bursts for the first few weeks but once you get the moisture level established, you can shorten the bursts. Also if you begin watering a little earlier than you think you need too after a substantial rain event, you’ll build momentum on that existing moisture and won’t need a long burst unless it gets very hot!

I hope this idea helps you manage your dahlias in this extreme heat- I know it’s eased my anxiety over them!

Disclaimer: I am not an irrigation expert- in fact, it’s one of my most dreaded tasks on the farm. If you are trying to set up an irrigation system for the first time, consult an expert- try out dripworks.com, rainflo.com, berryhilldrip.com - those are all good sources of information as well as great places to get the supplies you need. My goal here is to offer a different way of thinking about running your system that I have found to save water and increase my plant health.