I imagine a lot of it depends on the water source. Some cities get their water from wells, some from surface water (lakes, rivers, etc…) and these may be very different from rainwater in terms of mineral composition.
For example, well water can have different amounts of sodium and other minerals than surface water. In my area (Dallas), the city water’s moderately hard, and comes from a variety of lakes in the area. Plants grow just fine with it.
I suspect in the absence of something particularly plant-toxic in your city water, it’s likely that the growth differences you see are more due to the amount of water, rather than the type of water. Rainfall has a tendency to soak in deeper than sprinklers do, unless you water for extended periods. I’ve used drip irrigation (with city water) in the past, and never noticed that it was inferior to natural rainfall in any way, but then again, I usually water each plant at a trickle (1-2 GPH, depending on the plant) for about an hour, every third day.
Here’s mine. Holds about 10,000 gallons from roof gutter run off when it rains.
We aren’t connected to any other water supply. We don’t have “city water”. It runs through a filter and then into the house using a pump. It helps that we average 200 inches of rain every year.
I have a few tropical plants that I like very much. I have observed the same phenomenon as the OP, so a few years back I made a a 3 ft x 3 ft x 5 ft high plexiglass enclosure open at the top. Installed the misters and sprayers available from homedepot as part of their drip irrigation system, put the potted plant in the middle and hooked it up with the yard sprinkler system. I got the same growth rate and shiny healthy leaves within a few days much like after the rains.
My conclusion is that you do not get the same level of soil saturation no matter how careful you are with a hose sprayer system. In fact the guys in the professional nurseries use a similar setup - you need to saturate the soil and create a very humid environment around the plant.
For plants that like acid soil, that could very well explain part of the difference in growth.
I’d also vote for benefits of increased humidity, lowered temps and soaking rain for perceived differences between growth based on city water vs. rainwater.
Some think that the chloramine/chlorine in tap water isn’t beneficial for seedlings. I’ve experimented with purchased filtered water vs. tap water and can’t swear to a difference in growth/health.
Colorado is the only state in the US where it’s illegal to catch rainwater. Rainwater harvesting regulations state by state | Rain water harvesting and slow sand water filters In the other 49 states, catching the runoff from your roof, is perfectly legal. IANAL. Stories like the one about Oregon resident Gary Harrington are almost NEVER about actually collecting rainwater. In Harrington’s case, he built three dams on his property (two 10 feet tall and one 20 feet tall), blocking streams that flowed across his property, capturing enough water “to fill almost 20 Olympic-sized swimming pools”. Clearly that’s totally different from rainwater harvesting, which is perfectly legal in Oregon. Did an Oregon Man Get a Prison Sentence for Collecting Rainwater on His Own Property? | Snopes.com There are some places where collecting rainwater is restricted (such as limiting the amount you can store to less than 10,000 gallons) and you may have to follow building codes about what kind of tank, filters, hoses, etc. to use, but that’s not the same thing as prohibiting it.
Yellow crust could be from too much salt. Check with the city, they probably have a water analysis available for their water. Using strategic drip irrigation can help if the water has a lot of salts.
You could mix up your use of rain water and city water. Save some rain water for later in the season. Maybe get more barrels (or a tank).
The increased humidity and lower temperature from rain would help as well. You might also get run-off from elsewhere, and lose less to elsewhere, when the whole neighbourhood gets rained on.
Actually, Edwin, for several years my area has experienced abnormally COOL temperatures and average humidity levels in conjunction with a lack of adequate rainfall. Has it ever occurred to you that blazing heat and low humidity are not a prerequisite for drought?
For those of you who feel a high humidity environment is necessary for the average garden, (tomatoes, peppers, onions, zinnias, marigolds, lilac bushes, etc.) you’re simply wrong. Low humidity, in and of itself, is a gardeners friend. Conversely, high humidity causes a multitude of problems. I won’t bore you with all the details, but one key aspect relevant to this discussion is that high humidity inhibits plant respiration… It’s ability to “breathe” (take up water). Not good combined with a low rainfall situation.
Moist, humid air environments don’t do most garden plants, trees, or shrubs any favor. So, unless you all are referring to some type of air plant that is dependent on consistently high humidity, such as an orchid, let’s get off the “humidity” aspect that you associate with natural rainfall (it is very temporary). After all, the same condition is replicated by artificial watering, making the humidity aspect moot.
As to my ability to gauge an adequate depth of artificial watering: As mentioned before, I’ve been doing this for more than a few years, and am fully capable of excavating a 6"-12" hole in the ground to see if water has penetrated. I have, and it does.
Nevertheless, for those naysayers who arbitrarily conclude my technique is at fault, and thereby assume there is no difference between rain and my city water… Apparently you missed the part where I explained that I irrigate with stored rain water when necessary, with good results till it runs out. Then, when I resort to irrigating with city water, things go to hell.
As to those of you who have suggested that the Ph and/or hardness in my city water may be an issue… That is the most reasonable explanation put forth so far. (I still haven’t ruled out chloramine)
I took samples this weekend, and will analyze them Monday @ work… Later.
I feel the need to point out that you’re getting a lot of suggestions and in return you’ve been nothing but nasty. Even in your OP you weren’t very nice. On top of that, we can only work with what you give us. For example, when people started suggesting humidity related issues, you snapped back at them because your plants don’t require high humidity…as if we somehow magically know what kind of plants you have.
Furthermore " After all, the same condition is replicated by artificial watering, making the humidity aspect moot." isn’t true. Unless watering your garden somehow brings the humidity in that area up to 90+% for a few hours, natural rainfall is different.
Another thing, it’s annoying to hear things like " I’ve been doing this for more than a few years, and am fully capable of excavating a 6"-12" hole in the ground to see if water has penetrated. I have, and it does" when asked if you’re watering enough. Just because you said " I know how to properly water plants" doesn’t mean you do. Is it really that hard to say 'yes, I checked and water is making it down X inches" instead of being condescending to a bunch of people that are trying to help you. Plenty of issues are solved because someone thought they’ve been doing something the right way for years (and it’s always worked), but it turns out they were doing it wrong. For all we know (with this example), you’ve simply been lightly spraying the garden for a few seconds once or twice a week and been lucky. How are we to know that you actually checked to make sure the water is penetrating a full 12 inches down?
Relax, take it easy or people aren’t going to be so thrilled to help out.
