If you grow flowers for cutting then at some point you’ll want to reap your reward and harvest your yield.

Whether you’re a hobbyist back garden farmer or a professional flower farmer like me, then after months of nurturing your plants from seed to flower, you’ll eventually want to cut them.

Having worked so hard to get to this stage you want to be confident that when you do come to cut them, they last as long as possible in the vase.

In this article I’ve compiled seven years of experience in the cut flower industry (along with some scientific background) to give you all the information you need to make sure your cut flowers last as long as possible.

Cutting and Conditioning Flowers: The Science Behind it All

When plants produce flowers, they are doing so to produce seeds for the next generation. Flowering is often the end point of a plant’s life, especially if it is an annual.

When we cut the flower, we remove it from its water source and it begins to die. There are several factors that affect the speed of the plant’s death, some of which are very complicated processes. It’s only the ones that we can influence that we should focus on.

Plants are able to take up water from the soil below through processes that alter the pressure potentials of water. Water evaporates from plants in a process called transpiration, in which the leaves create a negative water pressure potential.

The force of attraction between the water molecules causes water to draw from the roots, and up the xylem of the plant into the leaves. Once cut, we want our cut flower stems to continue to take up water so that the cells remain full of water for as long as possible.

Changes in water pressure due to blockages in the stem, pH and dissolved substances can mean that water moves out of the cells, causing the cut flower to wilt.

Inevitably, our cut flowers won’t last forever. The main factors that we can manage that impact their vase life are:

Stage of harvest
Post harvest treatment
Water quality
Environmental temperature

I am going to cover how we can optimise all of these conditions for flower longevity, starting with cutting the flowers. It is worth noting that there are many variables affecting cut flower longevity, which vary from species to species.

It is worth doing vase life tests and reading up on specific varieties if you are having trouble with cutting and conditioning something in particular. The book Speciality Cut Flowers by Allan Armitage is an excellent reference for information on the stages of harvest.

Cutting Tips

Cut Flowers in the Early Morning or Around Dusk

The ideal time to cut flowers is either early morning or around dusk since transpiration at these times is at a minimum. Wind, sun and heat are all factors which increase transpiration, meaning picking at midday is usually not ideal.

2. Focus your Efforts in the Morning

Of the two periods, morning is the most preferable time to pick as the plants have been able to recover from moisture loss overnight and plant core temperature is cooler. A cooler core temperature will encourage greater longevity.

3. Cut with Clean, Sharp Secateurs

Dirty secateurs can be a source of bacteria, keep them clean to reduce contamination. Use sharp secateurs to minimize stem crushing. Crushed stems may not be ale to draw water effectively.

4. Use a Clean Bucket with Fresh Water

Dirty buckets can also be a source of bacteria. Keep them clean and use fresh tap water.

5. Cut into Cool Water in a Shady Area

A shady area is going to be the coolest place for your bucket while harvesting. Place stems in the water as soon as possible after cutting, to reduce the stem temperature. A cooler plant core temperature = longer vase life.

6. Cut at the Appropriate Stage of the Plant’s Life

Each type of plant has an optimal cutting period and this varies by species.

For spike flowers you want between a third and a half of the flowers on the stem to be open.
For daisy-shaped flowers like cosmos, you want the petals to be somewhere between just starting to crack open and half way there.
Some flowers like Achillea need to be fully open in order for it to last in the vase.

Read until the end for the right time of year to cut achilleas, zinnias, snapdragons and dahlias.

7. Cut the Stem at an Angle

Cutting the stem at an angle helps to prevent the xylem from becoming clogged or blocked. Cutting at a 45°angle helps to increase the surface area of the stem and therefore the amount of water it is able to uptake.

When picking flowers, I try to pick early in the morning or late at night and leave them to condition in the coolest, darkest place possible.

Once flowers have been pollinated, energy expenditure shifts from attractive flower formation to seed production.

Since petals begin to fall within days of pollination, picking flowers before pollination is ideal.

Ideal picking time is quite specific for each species but as a general rule pick flowers when the petals are beginning to unfold.

A Note on the Best Time to Cut Flowers

Although cutting in the morning is preferable, there are some advantages to cutting in the afternoon. As the plant has been photosynthesising all day, the plant will contain more sugars which keeps the plant going for longer.

The downside is that a higher core temperature may negatively affect vase life. In an attempt to combat this, we can practice pulse conditioning.

Pulse Conditioning to Extend Flower Life

To practise pulse conditioning the flowers are first put into tepid water about 32°C (90°F) for an hour, and then moved into cold water of 4.4°C (40° F). While the stems are submerged in warm water, they uptake water at a faster rate.

Next, by placing them in cool water, the stem’s temperature and transpiration rate will be lowered, keeping the stems full of water.

This is quite labour intensive however, and not everyone has access to temperature-controlled water. In the US many flower growers use a cooler but they are not so commonly used in other countries such as the UK where I am based.

Tips for Conditioning Cut Flowers

Keeping flowers cool is essential to prolonging vase life. Condition flowers in a cool dark barn, shed or room.
Flowers must be conditioned for a few hours before arranging them. You will notice how flowers go from looking a little sad to bright and perky after a few hours of conditioning.
Putting fewer stems into a bucket will help with the cooling process.
The presence of bacteria in the water can block the xylem and reduce the water flow into the stem. Keep water clean and remove any leafy material from below the surface of the water.
Keeping a vase in a cool place will reduce the rate of bacterial growth.
Lowering the pH of the water will reduce bacterial growth and has been shown to increase water uptake.
Adding sugar may also help to increase water uptake by the stems.
Many commercially produced plant foods are full of chemicals and heavy metals to kill bacteria and reduce pH. It is much safer to make your own, or just use clean water and vases.
Effective plant foods will reduce bacterial growth and provide sugars to the plant, think along the lines of vinegar or lemon juice and sugar.
It helps to re-cut flower stems every couple of days to assure water flow is maximised.
Provide fresh water every couple of days.

Best Time to Cut Popular Flower Types

When is the Best Time to Cut Achillea?

Achillea needs to have fully open flowers in order to prolong its life in the vase. Picked too early and it will wilt. The best time to pick is when you see pollen on the flowers.

Achillea can be cut right at the base of the stem and the foliage from the stem removed before placing in water. If harvested, conditioned and cared for properly, achillea can last 7-12 days in the vase.

When is the Best Time to Cut Zinnias?

There is a simple trick to testing whether a zinnia is ready to cut and this is known as the wiggle test. Lightly shake the stem and if the flower head wiggles indicating a weak neck, then it is not ready to pick. If the stem stays rigid when shaking then it is ready for harvest.

Zinnias can last 7 days in the vase.

When is the Best Time to Cut Snapdragons?

Snapdragons should be harvested when between a third and a half of the flowers are open on the stem. Cut low into the plant and place into water.

Snapdragons are geotropic which means they will adjust their positioning according to gravity.

Stems must be placed vertical in a bucket during conditioning otherwise they bend to adjust their orientation. This position becomes fixed after a few hours.

When is the Best Time to Cut Dahlias?

Unlike other flowers which are best picked when colour starts to show or the bud starts cracking open, dahlias must be picked when they are mostly open. Dahlias do not continue to open in the vase.

It is too late to pick Dahlias when the outer petals curl backwards and start looking brown and worn. Dahlias will last around 5 days in a vase, with pompon varieties lasting the longest due to their robust flower design.

Cutting and Conditioning Flowers for Extended Vase Life: Summary

Whether you're a beginner flower enthusiast or a dedicated flower farmer, the key to enjoying your hard-earned blooms for as long as possible lies in the art of cutting and conditioning.

From my own experience in the cut flower industry plus some scientific insights, I hope you picked up some valuable tips to maximize the vase life of your beautiful bouquets.

From choosing the right time to cut and employing smart harvesting techniques to ensuring clean water and proper conditioning, these steps can make all the difference.

Remember, each flower type has its unique requirements, so stay informed and observe the nuances of nature. Here's to vibrant, long-lasting blooms!

How to Cut & Condition Flowers for Longer Lasting Bouquets