I came back from work the other day and noticed that the plants in my hydroponic tower were wilted and dry. When I investigated, I could see that the plug which powers my water pump timer had somehow come out of the socket and no water had been pumping through my tower. I had no idea how long my plants would last without water or if it was already too late to try to save them. After switching the pump back on I did some research and here’s what I found.
As a general rule, most hydroponic plants can last between 1-2 weeks without water before the pressure inside the stems and leaves drops and they start to wilt. The time it takes for dehydrated plants to die can be longer but it depends on the type of plants being grown.
Although my plants were fine, it was a bit of a shock, especially as I had no idea how long my plants could last or if they were going to be ok. In this article, I’ll share what I learned from my experience in the hopes I can spare you the same worry and help you avoid the same issue.
How long can hydroponic plants last without water?
The table below sets out the approximate length of time different hydroponic plants may last without water before starting to wilt and when they are at risk of death from dehydration. I’ve combined data from my own experience in growing these plants hydroponically with additional online research.
Table 1: How long common hydroponic plants can last without water
| Hydroponic Plant Type | Time to Wilting/Drooping | Time to Dehydration/Death |
|---|---|---|
| Lettuce | < 1 week | 1-2 weeks |
| Parsley | < 1 week | 1-2 weeks |
| Cilantro (Corriander) | < 1 week | 1-2 weeks |
| Basil | < 1 week | 1-2 weeks |
| Spinach | < 1 week | 1-2 weeks |
| Tomatoes | 1-2 weeks | 2-3 weeks |
| Peppers | 1-2 weeks | 2-3 weeks |
| Chillis | 1-2 weeks | 2-3 weeks |
| Mint | < 1 week | 2-3 weeks |
| Cucumber | 1-2 weeks | 2-3 weeks |
Keep in mind that how long hydroponic plants can last without any water depends on a multitude of different factors and these times should be treated as a rough guide only, rather than determinate times.
A hydroponic plant’s resistance to drought can be affected by its type, root maturity, how hydrated it was before the water stopped, and the environment in which it is grown (i.e. outside vs. inside).
Size of the root mass
As a general rule, the larger and more mature the plant’s root mass the more resistant it is to periods of drought. Plants store both water and nutrients in their roots. Therefore, larger and more mature root systems are capable of storing more water than smaller, developing ones. Plants with smaller, shallower roots – such as lettuce – are therefore more vulnerable to drought.
The health of the plant
It may seem obvious, but healthy plants are more resistant to drought than unhealthy ones. Plants that are already suffering from nutrient deficiencies or other ailments will wilt and die faster if they do not receive the water they need. Ensuring your plants are well stocked with nutrients and minerals is therefore critical to improving their overall resilience.
Environmental factors
Environmental factors are also important in determining how long your hydroponic plants may last without water. For example, plants that grow in outdoor hydroponic systems may be more susceptible to direct sunlight, warmer temperatures (especially in summer), and wind which can dramatically reduce the time it takes for plants to wilt and dry up. Plants grown indoors, where the environment is more controlled, tend to last longer without water.
How often should hydroponic plants be watered?
How often you water your hydroponic plants depends on which type of hydroponic system you are using and the plants you are trying to grow. In my own set-up (aeroponic tower garden), I have had good success by sending water cascading over the roots of my plants for 30 minutes in every hour of daylight. I have an automatic hydroponic water pump timer to help me achieve this.
The same applies to other types of ‘active’ hydroponic systems, such as Ebb & Flow (aka Flood & Drain). As a general rule, washing the roots with a nutrient-rich solution for 30 minutes in every hour of daylight with the help of a timer tends to work quite well.
An example of Ebb & Flow hydroponics
I also have some passive hydroponic systems. For example, systems like Wick Hydroponics feed water to the roots directly by continually saturating the soil. In this type of passive system, no manual watering is required (bar keeping the reservoir topped up with water and nutrients.
An example of Wick Hydroponics
Is it possible to overwater hydroponic plants?
In hydroponics, it is possible to overwater and even drown plants without proper care. The principal cause of drowning results from a lack of oxygen near the roots. This is particularly common when the roots of plants are continually submerged in water that is not oxygenated to the right level (equal to or above 5 mg/L). The use of an air stone in some hydroponic systems can help to minimize this risk.
Can my plants recover after drying out?
In most cases, it is entirely possible to recover dehydrated plants provided that they have not gone beyond the point at which they can be saved. When I saw my plants were wilted and dry, I was worried I’d have to throw them out and start over. However, since it had been less than a week, I was able to recover nearly 100% of them simply by resuming watering.
It can take up to 2 weeks to fully recover plants, so you need to persevere and be patient. However, in most cases, you should see a response within a few days as the pressure in plants’ stems and leaves increases.
Table 2: Time before dehydrated plants become unrecoverable
| Hydroponic Plant Type | Unrecoverable (likely dead) |
|---|---|
| Lettuce | 2-3 weeks |
| Parsley | 2-3 weeks |
| Cilantro (Corriander) | 2-3 weeks |
| Basil | 2-3 weeks |
| Spinach | 2-3 weeks |
| Tomatoes | 3-4 weeks |
| Peppers | 3-4 weeks |
| Chillis | 3-4 weeks |
| Mint | 3-4 weeks |
| Cucumber | 3-4 weeks |
Should you occasionally let hydroponic plants dry out?
As a rule of thumb, it is not recommended to let hydroponic plants fully dry out. This is because roots can shrivel and become brittle when completely dried. Resuming watering over brittle roots can ‘shock’ them and cause damage. Like a rock, continually wetting and drying roots can even cause them to break.
In conclusion
Generally speaking, hydroponic plants can last between 1-2 weeks without water. So, should the worst happen and you lose access to water you should have enough time to rectify the problem before any damage is done.
Hydroponic plants that go without water, like most all other plants, will wilt as the water pressure in their leaves and stems reduces. However, fortunately, it is entirely possible to save them simply by resuming watering before they get too dehydrated. It’s more likely that not that your hydroponic plants can be saved provided action is taken within this window.