Optimising water use in containers with bedding plants

RHS project team
Dr Tijana Blanusa, RHS
Start date
31/01/2005 09:00:24
End date
31/01/2010 09:00:20

Watering, water deficit, dry soil, flowering, petunia, impatiens, bedding plants.

The problem

Bedding plants are popular landscape features in public parks and private gardens, as well as in containers and hanging baskets in town centres. Most popular bedding species such as Petunia x hybrida or Impatiens walleriana are, however, identified as ‘water demanding’.

With decreasing summer rainfall and increasing temperature, there is pressure on both home and professional gardeners to minimise water inputs. Consequently, bedding plants are often replaced in the landscape with apparently less-water demanding species. These alternative species rely on the foliage for impact rather than flowers, and are often generally less popular with the public.

We are keen to find out if, by changing the ways in which we water manage traditional bedding plants, we can continue to enjoy them in the changing climate.


A series of experiments are set up in the glasshouses at the University of Reading. Petunia x hybrida and Impatiens walleriana are used as model bedding species. Plants at plug stage are transplanted, singly or in combinations, into 2-litre containers with standard potting compost and grown for a period of five to 10 weeks.

A number of watering regimes are imposed where plants substrate moisture is kept either at 100% container capacity (control) or at various lower moisture concentrations (e.g. 50% and 25%). Changes in plant physiology (stomatal opening, photosynthetic capacity) and root growth are monitored, along with the ornamental parameters: floral bud and flower numbers, flower size and longevity, plant size.


To understand to what extent the amount of water given to plants can be decreased without compromising plants’ ornamental qualities.

To investigate how presence of multiple individuals and multiple species in a container affects water consumption and plant quality.

Benefits to gardeners

The project will provide answers on what is the best watering practice for bedding plants grown in hanging baskets and to what extent we can save water compared to traditional ways of managing hanging baskets.

Summary of results

Changes in climate and increased demand for water resources are likely to result in increased pressure to reduce water use in ornamental horticulture, especially by local government and domestic home owners. Rather than eliminating bedding plant displays outright, however, our data indicate that ‘acceptable’ bedding plant container displays can be achieved even when water use for irrigation of the containers is reduced by 67% below optimum. In reality, considerably larger savings are likely, as it is estimated that many containers are over-watered.

Advisory information

Tips on watering
Container maintenance
Water - the way ahead


T Blanusa, E Vysini and RWF Cameron, 2009, Growth and Flowering of Petunia and Impatiens: Effects of Competition and Reduced Water Content within a Container. HortScience, 44 (5): 1302-1307.

Blanusa, T, Cameron R 2009. Bedding plants in a changing climate, The Plantsman 8 (4), 250-253.

Blanusa, T, G Kostoulas, and RWF Cameron. 2010. Sub-irrigation of Petunia: benefits in dry summers. Acta Horticulturae. in press.

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