Hi, Sammy. I did post about water a year or two ago, but that's not exactly what I said. I think Pete41 has been arguing for very frequent, shallow watering in sandy soil, but I'm not sure what his routine is.

I am no great shakes as a gardener compared to many here, so we need to hear more about what people's watering routines are. Ideally, we would find out the minimum that produces very good results with a general soil type and climate type. Tivoli rose Susan, for example, said she gives about 1/2" twice a week on sandy loam on Long Island. That's about what I do. I think Berndoodle said she gives about 1.6 gallon twice a week by drip. That's well under an inch a week for large plants. I don't know if that's a survive-summer mode or a grow-and-bloom mode. Drip is of course more efficient than other ways of watering.

The deep roots, if any, do take up enough water for survival, but not enough for rapid growth. Not the top couple of inches, but the top 8", maybe just 6", are what sustains rapid growth. There are feeder roots right up to the surface under the mulch that will die if the top 1-2" gets real dry. However, with a good mulch and medium or heavy soil, most of us in the Eastern half can go 3-4 days between watering and keep the top layer moist. Your conditions are different, so you would have to try stuff and monitor the soil moisture.

So I opined that it's better to do a 1/2 watering twice a week than to do the traditional deep watering once a week, but I don't water every two days (as you were considering) except with new roses planted out from pots. I think if you water more frequently but less at a time (say 1/2"), you are probably still maintaining some moisture down to the 12" level, which is the target for traditional deep watering. If you water a full inch twice a week, you are probably wasting water downwards where it does no good. Apparently roses are not equipped to take up a lot of water from deeper than 8".

If you give only very light watering, say 1/4" at a time, this could be wasteful because half of it might stay in the mulch and evaporate (IIRC Pete doesn't use a conventional mulch, but again sand is a different deal). So maybe .5-.7" is the right amount to apply at a time in many gardens.

There are some studies to back up this approach. Greenhouse roses in 16" deep soilless mix packed over half of their fine roots into the upper 4" of medium, though the whole depth had moisture and nutrients. Greenhouse roses growing in deep sandy loam on grade did better when given around .7" every 5 days than when given 1" about once a week. They took most of their moisture from the upper soil. In a Texas garden, roses, as compared to other plants in the landscape, showed a marked preference for taking water from the upper 8" soil zone. Even St. Augustine turfgrass was deeper rooted (functionally speaking) than roses.

One inch is around 2 gal. on a 2 x 2' area, 4 gal on 3 x 3', and 8 gal. on 4 x 4'.

Sammy,
Our conditions are very similar, I am sure. I'm over in Texarkana. My roses grow and bloom all summer with only 1 watering a week. I have drip irrigation and each rose is on a 1 gallon per hour dripper. The climbers have 2 gallons per hour. During the summer, or anytime when it isn't raining, I water them overnight once per week. If I thought that they would bloom more with more water then I would probably water them more. But they bloom so much that I just can't believe that they could do any better if watered more frequently so I leave the schedule alone.
If any of you see proof of something different I may change my routine and break it up a bit and see if there are more blooms. But I don't think it's possible.
Carrie

So, Carrie, is that 12 gallons or 8? And what kind of soil do you have? I saw your pictures a while ago-- looking good.

Probably 11 gallons. But with the drippers, even the pressure compensating drippers that I have, the flow is variable.
Wow, I've never thought of how much water, exactly, that the roses are getting! 11 gallons x 140 roses = 1540 gallons, and I'm watering a lot of other shrubs, too.
But with the drip system, even after 11 hours or so of watering, the paths are still dry because all of the water goes right to the rose one drip at a time and there is no "overflow".
I may change my watering strategy based on what you said, Michael. I am probably overwatering if the roses don't use water deeper than 8". Using a drip, how many gallons do you think it would take to go down 6 - 8"? Is there any easy way to test it? (ie not with a shovel)
My soil is about 1' sandy dirt with clay underneath it. But each rose got around a 1.5'/1.5' hole and all of the native soil was taken out and replaced with compost from our wastewater plant.

I am so late in doing everything, but I have noticed that where I have the soaker hoses, the ground has really sunk. I don't know if I can successfully lift up some of the older roses, but I think I am wasting water. Once it gets down into that heavy clay, I don't think the roots will continue to absorb it.

Someone posted about how we tend to waste time and money on deep soaking. According to this person we only need to water the top few inches, and move on, but we do need to water frequently. This is interesting to me since I amend out soil, and grow in more pourous soil than our native clay.

If it wasn't you, Michael, maybe Mike Rivers. I don't think it was MAT, but maybe it was. I would not have read much about Pete's since he has sand, and we have no sand. Oh, well, in time maybe I will find the article.

Thanks for the responses, Michael and Carrie.

Sammy

Carrie, this is just my opinion (with I hope some information mixed in), but you might be able to save a lot of water and get equally good results. I think if you are willing to experiment, that would be cool, because a lot of people won't change what they're doing if it is successful, and you've been very successful.

So you have 12" of (probably) sandy loam over clay, and 18" rose holes filled with 100% organic matter. That's an unusual situation, but let's try to figure out what's happening to the water as you are now applying it. If it were spread around more, a 12-gallon application would in theory be enough to wet around a 5 x 5 area of sandy loam to a depth of 12". If the rose holes had been dug only 12" deep, then the clay subsoil would cause the drip application to spread pretty wide into the porous sandy loam. But as it is, the bottom 6" of the rose hole is probably filling with water from the heavy application and then slowly draining into the clay below. Water that goes into the clay won't come back, because clay has a stronger capillary attraction than the sandy loam. (If the soil were more uniform, it would pump water gradually up from the wetter deep areas to the upper areas being dried out by the plants' roots.) So I'm pretty confident that some water is being wasted. I guess your system is working because the muck in the rose hole holds enough water to get the plant through the week. Organic matter can hold a great deal of water, but there's no way to know how much for this particular stuff.

You asked how to monitor the effect of watering. This can be done with a simple probe, a pointed rod. I've done it with a thin bamboo stake, sharpened. Soil that is saturated or nearly so is much easier to push through than soil that is fairly dry. So you could probe the sandy loam when it is wet and when dry to feel the difference. Right after a heavy drip application, you could examine the soil surface outside the rose hole, under the mulch, to see how far out from the rose hole is the surface moist. Then you could probe those areas to see how deep the saturation goes. Then outside the zone of surface moisture, you may find that the sandy loam is wet further down, though dry on top (pushing is harder at first, then easier). Or maybe most of the water is staying in the rose hole and beneath it, because the muck doesn't want to give up water to the sand. That would be interesting to find out.

If it turns out that you're basically watering an 18" pot, obviously you could cut way back on the water. Here's what I would try. When it's time to start irrigating, probe the muck to see what it feels like, then run 2 or 3 gallons and go check out what happened at a couple of drip sites. How much water reached the sand, and how deep is the muck saturated? Later, some water will move deeper as the saturated zone drains. You may find that something like 3 gallons twice a week is enough to keep the roses growing well.

Insofar as you are watering the sand via the drips, I don't think it will hold useful amounts of water for a whole week in summertime. Also I'm not sure doubling up the drip on the climbers is a good idea. They will have wide-ranging roots, and it might be better to supplement by hand watering a wide zone around them rather than putting a lot of water in one spot. Or maybe the roots outside the hole will have dived down to the clay, which I guess would stay moist year-round.

Carrie, if you look into any of these things, I'd be interested to hear what you find.

Michael,
I am going to write it on my calendar to check it out next time I water. It rained this week so I may not be watering for a week or 2. But when I do I'll find this post and add to it.
Thanks for all of the info.
I'd write more but need to get back to work real quick.
Carrie