Sunflowers are pretty hardy plants that absolutely love the sun, hence their name.
In fact, they ideally need about 6 to 8 hours of sun a day to bloom fully.
But what about the wet stuff, how long can sunflowers go without water?
The answer does depend on whether you are growing them in pots or outside in the ground or whether you are asking specifically how long do cut sunflowers last without water?
Another factor is what stage of the growth cycle they are at.
Either way, in comparison to most plants, sunflowers do need a lot of water so you need to make sure your sunflowers are not left feeling thirsty.
So let’s take a closer look.
How Long Can Sunflowers Go Without Water?
If you are talking about cut sunflowers in a vase, they can’t go for much longer than a couple of hours without water. If you are growing sunflowers from seed when they are germinating they can’t go much longer than a couple of days without water. Once sunflowers mature and are above around 2 feet (60cm) in height, they can get by with water just once a week depending upon conditions.
Keeping Sunflowers in a Vase
How Long Do Cut Sunflowers Last Without Water?
Sunflowers are cheerful flowers that can really lift the mood indoors on any day.
So many people use cut sunflowers in a vase as a way of brightening their home.
But how long do sunflowers last when cut?
Well cut sunflowers require a lot of water, and if left without water for a few hours or more there is a strong chance they won’t survive.
Also unlike other flowers, it isn’t recommended to keep sunflowers chilled to prolong their life when you have cut them.
Ideally, if you pick sunflowers that are going to be cut and put in a vase, you should put them in water immediately to keep them from drying out.
This not only keeps them hydrated but also lessens the shock of being picked.
Once you have got your cut sunflowers in a vase you want to change the water regularly.
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You can replace the water every 2 or 3 days (or sooner obviously if the water has dried out), but replacing the water every day will maximize the life of the flower by keeping bacteria levels low.
It will also mean there is less smell when it is sadly time to put your sunflowers in the compost bin.
Most cut flowers last around 4 to 5 days but cut sunflowers that are well cared for can last for up to 12 days.
A few little tips, outlined below, can help you get the most out of them.
Tips to Get the Most From Cut Sunflowers
Tip #1: Cut the Stems Diagonally
If you trim around half an inch off the bottom of the stems every time you replace the water it removes any scar tissue that may prevent water from entering the stem.
This small action essentially makes it easier for the stem to absorb water and increases the lifespan of your flowers.
This works for all kinds of cut flowers.
Tip #2: Make Sure They Don’t Get Too Much Sunlight
If you are growing sunflowers they love the sun and can bathe in it all day.
However, when it comes to cut sunflowers too much sun will deplete their lifespan.
This is because the sunlight encourages them to act as if they were outside or in a pot and photosynthesize. However, they lack the resources to do it properly with no roots or soil etc.
You don’t need to keep them in a dark location, as that would obviously defeat the purpose of having them inside, find a cool location out of direct sunlight and away from draft vents or doors.
Tip #3: Add Some Floral Food
Floral food will give the sunflowers valuable nutrients and keep them looking nicer longer.
You can buy floral food or make your own.
A popular option is to add two tablespoons of fresh lime or lemon juice and one tablespoon of sugar to every four cups (one quart) of water in the vase. Adding a small amount of bleach (around half a tablespoon) can delay the growth of mold and bacteria.
Tip #4: Add a Small Coin to the Water
It may sound like an old wives tale but adding a copper-based coin can be beneficial to your cut flowers.
The copper deters bacterial growth. There are medical supplies infused with copper for this very reason.
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Growing Sunflowers in Soil
The Difference Between Watering Potted Sunflowers and Sunflowers Grown in the Ground
If you aren’t talking about displaying sunflowers for decorative purposes then let’s consider how you might be growing your sunflower.
Some people start growing their sunflowers in potted containers before moving them outdoors, some people grow them solely in pots, whilst many just grow them in the soil outside.
The bottom line is if you are growing your sunflower in a potted container it will require more water.
This is because its roots are confined to the container and cannot find moisture underground.
As a side note make sure your container has plenty of drainage holes as soil that is too waterlogged can be as bad for sunflowers as no water at all.
How Long Do Sunflowers Last Without Water When You Are Growing Them in Soil?
This depends upon what stage of the growing process they are at, but whether you are growing your sunflower outside or inside it will expect water fairly regularly.
This is most important when they are in their early stages of growth, which is when they require more water to help their stems develop.
There are various facts and figures out there, one estimate is sunflowers require 34 inches of water annually for best growth.
It has also been suggested they need at least two gallons (7.5 liters) a week and more in their early stages.
A rough rule of thumb is that as long as there is regular rainfall outside, say a good downpour a couple of times a week, sunflowers should grow fine.
How Much Water Do Sunflowers Need When Germinating?
When germinating I would recommend watering every couple of days, or daily if conditions are particularly hot and dry.
It is important to keep the soil around newly planted seeds moist and certainly moister than when it is growing above the ground.
At this early stage, it doesn’t have the roots to find moisture under the ground so it requires more watering.
How Much Water Do Sunflowers Need After Germination?
Once your sunflower seeds have germinated you have done a lot of the hard work.
Once your sunflower gets above around two feet (60cm) in height it will only require about an inch to an inch and a half of water during the growing season.
This probably means watering once or twice a week. As sunflowers mature so do their root systems, and they can seek out water underground more easily.
Water with a watering can or a sprinkler hose, moving out to around 6 to 12 inches around the plant so the water can penetrate the soil and reach the wider roots.
Make sure you apply the water directly to the soil. Water the leaves directly can lead to fungus and disease and see your sunflower leaves turning yellow or brown.
It is also equally important to make sure you don’t overwater your sunflowers.
The soil should never be dry and should never be waterlogged. It should feel damp and moist to the touch.
As you see the top inch of the soil drying out it is probably time to water again.
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Final Thoughts
So as you can see the question of how long can sunflowers go without water, doesn’t have a cut and dry answer (pun slightly intended).
If you have sunflowers in a vase on display they really can’t go very long without water. If you are growing sunflowers from seed, they need water very regularly initially, but then this becomes less of a concern as their root systems mature.
Regardless, don’t be so obsessed with ensuring your sunflower gets enough sun, that you forget about making sure it is sufficiently watered.
They are drought-tolerant, they are hardy, but they still require their regular fill of H₂O!
