Improving Vase Life of cut flowers

Calcium is commonly applied to cut flower crops as it is a key nutrient in ensuring good vase life and stem weight, both important quality parameters in the market. However, the common methods for testing calcium levels can give misleading results, as leaf tissue levels are not a good indicator of calcium levels in other parts of the plant.

Here we discuss how best to monitor calcium status in cut flower crops, and strategies for improving calcium fertilisation in two example species - roses and chrysanthemums.?

To understand how to improve calcium nutrition in flower crops we first need to understand how it moves through the plant and is absorbed.

There are three main factors that influence the effectiveness of calcium fertilisation on flower crops, understanding them can help farmers make the best choices for improving vase life. The three factors are:

1. Transport

Calcium is not phloem mobile, so unlike most other nutrients it moves through the plant with water via the xylem. This means that movement is upwards and outwards and mass flow of calcium is towards the parts of the plant with highest transpiration.

The upper leaves get the lions share of access to calcium, and other parts of the plant like flowers, of shaded leaves get less throughput.

2. Absorption

Calcium enters plant tissue from the water moving through xylem via active transport, it can not enter passively. The absorption of calcium into plant tissue is directly linked to auxin (a plant hormone) levels; parts of plants lower in auxins are less able to absorb calcium.

Applying conventional calcium fertilizer to parts of plants that have low auxin levels does little to improve calcium content.

Auxins are not evenly distributed in flower crops. New leafy growth is high in auxin and can easily absorb calcium, but flower petals and older leaves lower down the stem are lower and inherently less able to absorb calcium no matter how much is applied.

3. Stress

Stressful growing conditions have a marked effect on calcium status in plant cells. When plants experience poor growing conditions they synthesize more of a hormone called Ethylene. One of the effects of ethylene exposure in plants is the movement of bound calcium in cell walls to the interior of the cell. The calcium is used as an 'on switch' for stress signaling, but this leads to a weakening of cell walls, an increase in disease susceptibility, and a reduction in vase life.

Plants can have a good calcium status but become low during stress periods. in petals and older leaves it can be hard to replace regardless of the quantity supplied to the crop in a fertilization program.

When we apply these three basic principles to different cut flower crops we can understand better how to improve vase life. In this article, I will take two widely grown cut flower crops that need a different approach to illustrate how plant physiology can help agronomy.

Best vase-life strategy for roses

In cut roses, the vase life is predominantly determined by petal quality. Petals falling, or contracting botrytis are both correlated with low calcium levels.

Below is data taken from a study in the Netherlands. We can see that there is a huge disparity in calcium content between the petals and leaves.

It is common practice for rose growers to leaf test for calcium. However leaf tissue levels of calcium in roses are a very poor indicator of petal level; It is the petal Ca level that correlates with vase life, not leaf level.

Albina is Levity’s unique calcium fertilizer, it contains a proprietary chemistry (LoCal) that improves calcium absorption in parts of plants with naturally low ability to take in calcium. It can be used to improve vase life in cut flower crops.

In roses, the use of Albina can improve calcium levels in the petals when applied regularly during flower development. Lower levels are needed as the calcium can be properly absorbed.

Best vase-life strategy for chrysanthemums

in contrast with roses, Chrysanthemum vase life is predominantly determined by the deterioration of lower leaves, whereby lower leaves tend to die off before the flower drops petals.

Here leaf analysis can give us useful data, but the focus must be on lower leaves. It is easy to fill leaves up with calcium when they are growing, as they get good throughput of Ca via mass flow, and young foliage is high in auxin and capable of absorbing Ca easily.

The problems with chrysanthemum shelf life correlate strongly with low Ca levels in lower leaves and stress during the growing season- these two factors are linked as stress removes calcium from cell walls.

Because cut flowers are grown at high density it is very difficult to replace lost calcium in lower leaves following depletion due to stress. Shaded foliage lower down the plant recieves little water so mass flow of calcium is low towards harvest. Old leaves have low levels of auxin as they are no longer actively growing, so they also struggle to absorb calcium.

Simply upping levels of basic calcium fertiliser late season will therefore have little impact on vase life - a more refined approach is needed.

Managing stress alongside applying a more advanced calcium that can be absorbed by mature leaves (Albina for example) is a good strategy to improve vase life in chrysanthemum.

Both Levity's advanced calcium Albina and it's anti-stress product Indra are proven in independent replicated trials to impact stem weight, and vase life. Both products impact on calcium, Albina by improving levels in mature leaves and flowers, and Indra by preventing loss of calcium during stress periods.

Here can see results from independent trials in Colombia that was published at the ISHS XII International Symposium on Post-harvest Quality of Ornamental Plants at Wageningen University in 2023.

Summary and advice

Cut flowers are not one crop, there are many species and varieties and the same issue (vase life) needs different agronomic approaches for different types of cut flower. A good understanding of where the problem is, and what is creating it can help agronomists improve it. Here are my top tips:

1. For calcium test the part of the plant that has the problem.
2. Use a calcium product that can be absorbed by flowers and older leaves like Levity's Albina.
3. Manage stress agronomically, and consider using a stress busting product like Levity's Indra.
4. Do your research, is there scientific data on the inputs you are using?

For more info check out Levity's cut flower crop guide

References

Baas, R., Marissen, N. & Dik, A. 2000 Cut rose quality as affected by calcium supply and translocation Acta Hort. 518 45 54.

Dodgson, J., Weston, AK. and Marks, DJ. 2023 Chrysanthemum yield increased using targeted foliar fertiliser applications, ISHS XII International Symposium on Post-harvest Quality of Ornamental Plants.