Horticulture Notes December 2007

David Davidson, my colleague, is the CAFRE Cut Flower Development Adviser. In recent seasons, his work with new and existing growers has identified some exciting lines of production. However, to ensure long term success, he always emphasises the importance of paying attention to the basic rules for quality growing.

In outlining these points, David told me, “There are clear opportunities to produce more cut flowers in Northern Ireland for local and export markets. However, whatever the market, we must pay careful attention to tunnel and soil management to be successful. Now that the main production season is past, it is a good time to address these important routine tasks.”

Sweet William (Dianthus barbatus) can be grown under protection to supply early local markets

Cut flowers can be produced for harvest between June and October, in polythene tunnels with side ventilation. The season for planting these crops starts in early March and ends in July. Hence, anyone considering growing cut flowers next season should ensure the tunnels are erected before February 2008. This will allow time for a full cropping programme. There are a number of local companies experienced in the supply and erection of polytunnels. You should also contact your local planning agency for advice on planning regulations which may effect your project.

Polythene is degraded by UV light, so you should plan (and budget) to replace the tunnel cover every five years. This will ensure that light penetration is kept high enough for healthy crop growth. With age, polythene perishes, especially at stress points. Any tears will develop during winter storms and this could result in the tunnel being re-clad before the recommended five year renewal. Avoid this unnecessary extra cost by inspecting all tunnels for signs of polythene damage. Repair damage using the appropriate repair tape available through your tunnel supplier.

Pests and diseases can over-winter inside polythene structures and infect next year’s crops from an early stage. It is important to clear debris thoroughly from ground surfaces and to wash the inside of polythene each winter. Algae also grows on inner and outer surfaces of polythene covers, causing a big reduction in light penetration. A loss in light levels can result in reduced flower stem quality. So, while tunnels are free from crops, you should clean algae from inside and outside surfaces.

Soil needs to be properly prepared prior to planting any cut flower crops. The deadline for this work is early March to allow a full cropping programme to be undertaken. Weeds can easily overwhelm a cut flower crop and soil should be treated for weeds prior to planting, using a suitable soil sterilant such as dazomet.

The correct pH and nutrient level prior to planting is essential to guarantee healthy growth and flowering. Collect soil samples from your planned cropping area within the tunnels and send for analysis through your local DARD Agriculture Development Office. Ensure that you ask for a horticultural soil analysis as opposed to an agricultural analysis, so that nitrogen and salt conductivity levels are tested. This information is required to work out the nutrients required for growing the cut flowers in protected structures. Ask for a copy of these results to be sent to the Cut Flower Development Adviser, who will recommend appropriate actions to correct any imbalances.