Of course they don't refer to rain with that statement!! You can't do anything about that. But overhead irrigation is typically discouraged. It can increase relative humidity, the chance of fungal diseases and other pathogens (specially late in the day), insufficient water may reach the root zone were it is needed (shielded by aboveground foliage) and 30-50% of the water from overhead irrigation is wasted, lost to evaporation before it even hits the ground.

If you have the choice, drip irrigation or soaker hoses are preferred. Or low volume emission irrigation systems. Water delivered directly to the root zone and not to the foliage.

There is an old gardener's joke where the punch line is 'God, you're doing it wrong.'

There are plants that, for a variety of reasons, have problems with 'overhead watering', and the associated humidity, no matter who is doing it. The East Coast doesn't grow those. They also don't tend to need a lot of water, from whatever source.

On the extremely rare occasions I think I should water things, I also dig out the sprinkler. The last time was a couple of years ago. I had picked up a really cool, really expensive Gardenia sprinkler for $15 at a garage sale, and mostly just wanted to see if it worked.

Usually refers to potted plants and seedlings and just means add water to a tray or saucer so the plant takes water up through the rootzone.

As well as preventing pathogens such as rust spores, spreading through the foliage - there can be implications for soil structure. Every time water is added from the top - whether (heavy)rainfall, sprinkler or hosepipe, there is a tiny, but incremental risk of soil compaction. My D-i-L is an orchid grower and always waters from below to maintain high friability and a loose structure in the soil. Fragile seedlings can be very sensitive to soil disturbance so I (try to) water my trays, which sometimes stand on capillary matting, sometimes sunk in sand or sometimes, just in standard seed trays.

For my garden plants, I'm not that careful on how I water, more when. AM if I can or with enough daylight left to dry. New plantings I use a hose and wand. For established landscape plantings I use a sprinkler.

I think a lot of don't water from the top is humans aren't always very good at replicating rain conditions in the home gardens. Often we use sprinklers in the sun, watering cans and sprayers that deliver thunderstorms instead of gentle showers, and so on. Sometimes it's just easier to bottom water seeds and seedlings, or unnessary to top water when establishing when it's the root zone that needs it more. Soaker jugs, ollas, and soaker hoses can better mimic the water flow that comes from gentle rain, even when it's sunny out and should not be raining. I do a lot of bottom watering while growing seeds and seedlings, establishing perennials. I use a lot of ollas and soaker jugs in the gardens and outdoor containers.

I do some overhead watering. When I have seed that gets soft pressed into soil, I tend to use a spray bottle and gently spray them into place. With some of my seedlings as they get to the mature point of finishing hardening off and such, I will water a bit from overhead with a watering can to better simulate spring rains if there isn't a handy rain during that time. Sometimes it's more gentle to water with a can and keep the cap closed during the thunderstorm that the plants aren't quite ready for yet.

There is also something to be said for mulch and how it is sometimes used or misued. That can have an impact on how top or bottom watering works in different gardening situations. Sometimes an issue with top watering can be folks think they are deep watering their plants when they are deep watering their mulch and sort of watering their plants.

In dry western climates I don't think it matters one iota if you do overhead watering. Humidity and perpetual wetness is never going to be an issue.

Some of the advice against overhead watering seems to stem from conditions in the U.K. (often chilly and damp, with accompanying mold/fungal problems) where some noteworthy garden writers originate. Similarly we're told not to water house plants late in the day for fear of damp leaves overnight supposedly promoting disease, though I've never found this to be a problem if soil drains freely, in a house where temps don't drop below the mid-60s at night.

It often rains at night and somehow gardens survive. We had over three-quarters of an inch of rain overnight here, and I felt no need to run out early today and towel the leaves dry. :)

In the great majority of situations, overhead watering is fine.

Let's make it clear what is being discussed. Not houseplants and not seed starting issues. We are talking about inground planted outdoor plants. And there is a very distinct difference in water pressure and volume between overhead irrigation and natural rainfall, whether it comes during the day or at night. A significant number of plants can develop issues, typically fungal or bacterial, if they are routinely deluged by overhead irrigation. Especially those in the Prunus genus. And they can even be afflicted with problems just by getting doused by regular rainfall as well!

All verifiable from various online horticultural sources.

Yep, it is considered the kiss of death to water paeonies from the top (cos wilt). And yep, always the dreaded phytopthera on our potatoes in a wet summer.

Interesting comments.

Sorry not to have been back sooner, I've been planting seedlings and yanking weeds.

Thanks for the thoughts!

another vote for watering verly close to the ground, not all aver the plant

I do this for almost anything in my alottment,

especuially Tomatoes, Dahlias and the berry shrubs and raspberries

there definetely is a fungus issue as mentioned several times above

in my world.. warped as it is.. it means dont INTENTIONALLY wet the leaves ...

and dont argue with how God does it.. its not relevant to you wetting all your plants down in the evening... if you want to do it in the morning.. and they have all day to dry.. knock yourself out ..

dont let you plants go into muggy darkness wet.. or you will end up with molds and mildews ... its the rose growers lament ... and then you are spraying every few weeks with fungicides and mildewcides ...

also.. dont let your automated LAWN sprinklers.. wet your pots at night either ...

ken

Here's an article tackling common watering myths, including the idea that overhead watering is bad because fungal diseases will take over, or that if the sun comes out, water droplets will act as tiny magnifying glasses and burn leaves (not so).

"MYTH: OVERHEAD WATERING WITH A SPRINKLER IS BAD

Yes, it's usually best to apply water directly to the soil around plants rather than watering with a sprinkler. More water reaches roots. Less water is lost to evaporation. Foliage stays dry, minimizing disease problems.

But there are times when an overhead shower is called for. During dry, windy weather a thin layer of dust can build up on leaves, reducing the plants' ability to photosynthesize efficiently. Some insects, including aphids and spider mites, can be kept in check by simply hosing them off plants. Finally, heat-stressed plants that have wilted even though their roots are moist can get some relief from a cooling shower."

https://www.gardensmart.tv/?p=articles&title=5_Watering_Myths_Debunked

https://s3.wp.wsu.edu/uploads/sites/403/2015/03/leaf-scorch.pdf

Again, if climatic or seasonal conditions (i.e. persistent cool/damp weather) favor disease, caution with watering makes sense. And early morning watering is best, if your schedule permits it.

There is no link accessing your article.

And yes, there are myths associated with overhead watering, the biggest is that water droplets on the leaves in sun will scorch or burn the foliage. Not gonna happen!!

The most critical aspect with overhead watering is the timing. Early in the day is better. The dewpoint is higher so less water is wasted to evaporation. And water on any foliage has plenty of time to dry before sunset and a higher dewpoint/higher humidity at night encourages fungal issues.

btw, most strains of powdery mildew are water phobic, meaning that the fungal spores will not germinate in the presence of water and spraying or hosing down susceptible plants can help to deter disease development.

So yes, there are reasons overhead watering can be beneficial but it is still a less efficient and more wasteful process than root watering.

Rob, we need more context. Just a blanket statement "overhead watering is bad" or "good" obviously does not apply to all plants everywhere and is too vague to offer you any useful feedback. What plant was this info regarding? Was the info given in the context of outdoor or indoor growing? What location or climate was the advice supposed to be for?

See links provided in my last post.

Here's another reference (agricultural) showing no significant difference in disease incidence when comparing overhead and drip irrigation: http://journals.ashs.org/horttech/view/journals/horttech/32/1/article-p39.xml

As mentioned previously, there are situations where excessive watering (not necessarily overhead watering) can be problematic. But for the great majority of American gardeners, alleged disease hazards from sprinkling your garden are about as big a worry as "the hazards of disease which may be transmitted by paper towel litter"*. :)

*a message printed on hand dryers that have replaced paper towel dispensers in many public restrooms.

The proliferation of shothole disease in Prunus species is directly related to overhead watering!

https://ipm.ucanr.edu/PMG/GARDEN/FRUIT/DISEASE/shothole.html

https://www.marinij.com/2022/04/01/what-to-do-if-you-discover-shot-hole-disease-on-your-plants-or-trees/Prunus

https://getplanta.com/article/treatment/treatshothole

From Wikipedia: " Wilsonomyces carpophilus (the pathogen that causes shothole) can remain viable for several months and spores are often airborne. Since the fungi thrive in went conditions, overhead watering should be avoided. Remove and dispose of any infected buds, leaves, fruit and twigs. Shot hole disease is a major concern of the stone fruit industry. It is estimated that 80% of the California almond crop may be infested with shot hole disease, resulting in a potential yield loss of 50-75%."

It may not affect ALL gardeners but Prunus is a large genus with a lot of common garden plants and most stone fruits. It could well be a plenty big worry!!

So you're talking about large scale crop farming?

No, I am talking about home gardeners that may have English or cherry laurel hedges. These are major landscaping plants in many parts of the country. Or grow purple leaf plums, ornamental flowering cherries or fruiting plums, cherries, apricots or peaches.

OK, that's specific enough, thank you. I don't know why someone would water a tree that way, but that's good info to have if they wanted to. But trees shouldn't need water. That seems odd to me, backing up a step from the method to wondering about watering a tree at all. Maybe it is baby trees in a newly planted orchard.

I don't doubt that if one were in the luxurious position of choosing a sprinkler system vs. soaker hoses. the soakers are the better choice. I don't know much about that kind of stuff, but the sprinklers I've seen don't throw water very high. I'm not trying to argue, I don't have a motivation in this and don't lean one way or the other on the issue. But now that it has been brought up, it does seem interesting. Just trying to understand why this conversation is happening and imagine the scenarios where trees are getting non-rain-water from above.

Any time there's a large monoculture of something, problems can get out of hand, vs. single specimens with plenty of air on all sides. The close quarters of crop specimens could be a factor in regard to the quote about fruit industry.

It's true that when Zinnias need to be watered, it causes the spot fungus to show up and start making the leaves ugly. But that doesn't bother me. They're annuals and look pretty until they're done, one way or another. Since they planted themselves, I don't try to micro-manage them except to give water if they're wilty.