July is the cruelest month. At least for roses here in Houston. Temperatures are rising and rain is often just a memory. Watering our roses in not just a luxury. So let's run through some tips for summer watering in Houston.
Obviously, roses need water to survive. And our summer heat increases that need. But just as importantly, the roots can't take up any of the nutrients we add to the soil unless these nutrients are in a soluble (liquid) form. So if you want your roses to use those expensive additives your have sweated to add, you must water regularly so the additives can dissolve.
How Much to Water
Houston is big. Just because it rained an inch at the airport doesn't mean your yard got a drop. I recommend you get a rain gauge so you will know how much water has fallen on your yard. The goal is to put one to two inches of water on your raised rose beds each week. Most weeks you will have to supplement the water that falls from the sky. Put a tuna can near your waterer and see how long it takes to fill it with an inch of water. Now you will know how long you have to water to make your quota.
How Often to Water
Houston roses should be in raised beds, with at least two to three inches of cooling mulch over the roots. Raised beds mean we don't have to worry as much about drowning our roses. But those raised beds dry out fast. So I recommend you water two to three times per week. Just divide the weekly dose among those waterings.
When to Water
I recommend you water between 5 am and 6 pm during the summer. I do not recommend watering during the night or just before bed. Why? Because the longer the leaves remain wet, the more likely blackspot will flourish. Water when the sun is out so your leaves will dry off quickly.
I use PVC pipe and Dramm nozzles to water my roses. Dramm nozzles throw a pattern that is approximately 36 inches in diameter, which is perfect for my rose beds. And the pattern is horizontally flat and low-which helps keep water off the leaves. Dramm nozzles now come in both 360 degree and 180 degree patterns.
With the Dramm system I can see that the bed is getting wet. I always worried about this when I used leaky pipe and drip systems. Plus, it takes more water than a drip system puts out to dissolve any granular fertilizers you have added for your roses. And rose roots only take up nutrients that are in solution.
I use the Gardena quick-connect hose end snap system of couplers on my hoses and accessories. With this system I don't have to screw on the hose connection. I just snap them in place. This saves time, aggravation and effort. The Gardena brand is widely available at better hardware stores in Houston.
I also have a timer at the hose bib to control how long I water my roses. That way, I don't have to remember to turn off the water and I don't risk drowning my roses (or declaring bankruptcy when I get the water bill).
One last tip. If you aren't exhibiting your roses (where such things are prohibited), you should try an anti-transpirant for your roses. I have used both Cloud Cover and Wilt-Pruf. These products add a glossy coating to the leaves that slows down the rate the roses transpire moisture. As an extra benefit, studies have shown that the coating also inhibits blackspot by making it harder for the fungal spores to attach themselves. Just remember to apply regularly so new leaves will be covered. And get your car washed. We need the rain.