Join the RHS today and support our charitable work
The new app packed
with trusted gardening know-how
RHS members get reduced ticket prices
RHS members get free access to RHS Gardens
Free entry to RHS members at selected times »
Reduced prices on RHS Garden courses and workshops
Watering, water deficit, dry soil, flowering, petunia, impatiens, bedding plants.
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.
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.
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.
Tips on watering
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.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.