There are a few accepted rules in gardening, and none come with more flexible terms than those surrounding watering plants. Exactly how and when you water your plants has big implications for their health, but how many of our unwritten rules should we take as gospel?
We’ve run trials, and tested the boundaries here at Tiny Garden Habit, so you don’t have to. Here, we’ll take a look at the effects of watering plants at night; the pros; the cons; and everything in between.
Is watering at night bad for plants?
Watering your plants at night is the last resort, but it won’t kill your plants. While watering at night isn’t necessarily bad for your garden, it’s certainly not good. However, there are some caveats, with some species preferring a nighttime drink, and others well adapted to cope.
Take native plants, for example. If you live in the southern states, and you’ve got a productive no dig garden, rammed full of gorgeous butternut squash, they are very well adapted to that climate, so will take night time or evening watering in their stride.
However, tropical, or non-native species that are already stressed in our climate will need a little more consideration. Think tomatoes, cucumbers, or melons. Mildew is a big problem, and so is southern blight, which takes hold when moisture remains humid for longer than usual.
Can you water indoor plants at night?
Watering indoor plants at night is almost always a bad idea. Indoor plants are indoors for a reason they need to be coddled and gently looked after, in very artificial conditions. That can be the same for indoor seedlings on heat mats, or houseplants. Either way, they are indoors to give them more heat.
Plants with artificial heat are susceptible to damping off and fungal infection. Peppers in particular will fare badly if they are watered without sunlight to help balance the moisture.
Can you water vegetables at night?
For mature vegetables out in the garden, in raised beds, or growing in borders, watering at night is better than not watering at all, but should be avoided where possible.
Greenhouse crops should never be watered at night, as water will simply sit around the top soil causing humidity or, even worse, drain away completely while plants sit dormant for the night.
So yes, you can water vegetables at night, but watering during the day, particularly in the morning is better for them.
Can you water garden plants at night?
During heatwaves, any water is better than no water, but morning watering is by far the most effective, and economical use of water. Watering in the evening in hot weather tends to increase humidity, which is especially prevalent at night time.
In spring or autumn, natural rainfall will be adequate for your garden plants, whatever time of day it is.
Reasons not to water plants at night
But why, I hear you ask, potentially a little frustrated with these baseless rules. Well, watering plants at night is widely accepted to increase humidity, but there are actually quite a few tested and accepted problems directly caused by watering at night.
- Winter damage / Frostbite
- Root rot
- Wet foliage / humidity
- Transpiration
- Water loss / Wastage
Winter damage and frostbite are caused by watering at night
In zone 4 or lower it’s very possible to get temperatures around freezing as early as October, which is still well within the growing season for many vegetables. And in spring, unexpected frosts can hit as late as April. Last year, we had a shock frost in May (Zone 9), followed by flashes of snow in June.
In those conditions, watering at night, when the temperature is at its lowest can actively cause frostbite, and ice sheets, and allow freezing water to permeate the soil, slowing the whole growing season down by a couple of weeks.
Watering at night can cause root rot
Watering at night adds moisture to the soil when plants need it least. If plants don’t need water they will just ignore it. If plants ignore water it will more than likely sit around their roots, creating morning dew and higher humidity the following afternoon. In those conditions, fungal infection can damage plant roots, causing black root rot, which is incredibly hard to cure.
Wet foliage and humidity increase the risk of fungal infection and blight
Always water your roots, not leaves. That’s the golden rule of watering, but it can be surprisingly hard to avoid. Not only does watering at night increase the basic risk of accidentally hitting foliage, but it increases general humidity in the still evening air. This creates moisture on foliage and stems, which can cause blight on many vegetable crops.
Transpiration is most common at night
Transpiration is rare in vegetable plants, and still uncommon in most ornamental garden plants. However, tropical house plants, particularly those with waxy leaves and aerial roots have a tendency to self-regulate their water through transpiration; the process of losing water through cell walls in the leaf.
Transpiration is actually a positive sign that your houseplants are self-regulating, but when you water late in the evening or at night, they are basically just doing it to get rid of water they don’t need or want.
Watering plants at night is wasteful
Perhaps the most important reason of all, to avoid watering plants at night, is that it is simply wasteful. You can make so much more of your water in the late morning, or late afternoon and your plant will use every last drop.
What time of day to water plants, and how
So if you can’t water at night, then when should you water your plants? Let’s take a look at the most effective times of day to water, and how to water to best effect with each:
Morning
The best time of day to water plants is in the morning. Watering in the late morning, between 9 am and 11:30 am is the best way to water plants without wasting anything. Plants tend to respond better to morning watering, particularly while they are fruiting.
Afternoon
Watering plants in the afternoon, when the sun is out, and the weather is nice, is by far the most enjoyable time to water your garden. However, it is also the most wasteful, with around 3% of water typically lost from hosepipes before it even reaches the ground, and a further 2% lost from evaporation from the soil surface in summer.
Evening
Late afternoon or evening watering is essentially the same as watering in the morning. You waste less water in the cooler, stiller, air, and plants are still fairly receptive and actively growing before sunset. However, there is limited daylight left at this point, and plants will stop photosynthesizing, and start transpiring and releasing gas and water through their leaves, disregarding the water at their roots until morning.
Night
Watering plants at night is ok if you have no other choice, and doesn’t get in the way of your other daily routines. It’s also very unlikely to have a serious negative impact on your plants if you do it carefully, avoiding foliage and in smaller amounts. If you’re unlucky though, it does present several challenges, as we’ve shared throughout this article.
What plants benefit from being watered at night?
Now, this might seem counterintuitive, but all is not lost. There are some plants in the garden that actually perform better with late evening water. Take nicotiana or night-scented stock. They actively produce nectar in the evening, filling your garden with sweetly scented fragrances, and in some cases, helping to distract pests (moths in particular) from your edible garden.
During a heatwave, watering your bed and borders at night is also not a completely bad idea, as most shrubs and perennials will be desperate for any moisture they can get. Native plants in particular are well used to evening rainfall, so watering them at this time is fine.
Conclusion
If you have no other choice but to water plants at night, due to work patterns, lifestyle, or just plain old forgetfulness, then any water is better than none. But, if you’re really serious about giving your plants the best care possible, aim to water in the morning, which will give most plants exactly what they need, when they need it.
