Horticulture notes June 2008

Osteospermums (Cape Daisies) are a popular pot plant which can either be transplanted into the ground for summer display or be used in container planting. Their colours range from whites, yellows to purple hues with highlighted centres making them wonderful plants for beautifying the home.

Eight of these varieties were demonstrated at Greenmount Campus recently. They were potted into 13 cm pots (42 pots/m²) during week nine and those under glasshouse conditions were marketable by week 19 to 20. Those grown in tunnels were three weeks later giving the opportunity for either early or late crops. Growth habit for each variety is also different and needs to be taken into consideration when choosing which to grow.

For crops grown in the glasshouse growth regulation (0.4ml/l chloroquat applied as a drench) was required whereas those in tunnels do not require any. In general, reduced-peat growing medium (25 percent and 40 percent peat reduction) can produce a more compact plant which can further be enhanced by some application of a growth regulator. However, the two varieties tested responded differently.

The cost of plant material range from 13 pence to 51 pence per plug depending on the source (Table 1 below). Plants from all the suppliers produced quality crops at the point of sale. Production in 13 cm pots have the added quality compared with the industry standard in 10.5 cm pots and makes them more saleable when there is an oversupply (and hence reduced price) in the smaller pots.

Table 1 Cost of plant material based on catalogue prices 2007/08

For further information on growing Osteospermums or using of peat reduced medium please contact Teresa Maguire tel 028 9442 6694 or email teresa.maguire@dardni.gov.uk

May’s exceptionally dry and warm days gave ideal conditions for pollination and fruit set.  Such a welcome period of weather also has its potential problems.  Growers remarked on the rapid development of powdery mildew disease and fruit tree red spider mite pest (FTRSM) in some orchards.  Powdery mildew responds well to demethylation inhibitor (DMI) fungicides (for example,’Systhane’) or triazoles such as ‘Indar’ and ‘Topas’.  These can be included in your regular apple scab spray programme.  Control of FTRSM is also straightforward, but please bear in mind that the summer treatments of ‘Masai’ or ‘Sequel’ can only be applied once per year.  For this reason it is wise to check if natural predators are present in the leaf canopy.  Populations of these beneficial mites (‘typhs’ and Anystis baccarum) build up over time, so you may find that chemical control can be avoided if FTRSM is not a regular problem with your orchards.

Every year is different, but we can anticipate some of the likely health issues due to the prevailing weather conditions.  In a hot, dry summer, you might expect the following pests and diseases to be of concern:

If we have a cool and damp summer, it is more likely that you will find the following problems:

Frequent walks through your orchards are good health management practice.  Spotting symptoms early gives you plenty of warning to plan for effective action in time.