Why don’t roses open fully
The arrival of wet weather often brings with it a wide range of plant diseases and disorders – none more disfiguring than rose balling in which the flowers fail to open. Although this can occur pretty much any time when roses are in bloom, it is regularly seen in autumn, at the end of the flowering season.
It is caused when the petals of the flower become fused together by moisture that settles between them. Without air, the damp cell surface of the petals starts to break down slightly, gluing them to their neighbours to prevent them from expanding and the flower from opening. The effect is compounded during alternating sunny spells when the tissues dry and effectively ‘weld’ the petals together.
The phenomenon is most common is heavily double flowered rose blooms – those with many petals. It is also problematic in varieties that have well-defined cup shaping to the individual petals. In addition it is more common in very wet seasons, where periods of drenching rain are interspersed with sunshine. In many cases, especially in autumn, a secondary infection of grey mould (botrytis) can occur on the blooms, but this is generally not the initial cause of the balling.
Flower balling can occur in other heavily petalled double flowers, most notably peonies and sometimes in camellias.
How can I prevent rose flower balling
Heavily petalled flower forms are best planted in open, airy and full-sun locations where their blooms stand a better chance of drying out between rain showers. Opening up rose bushes by pruning to outward facing buds, before growth starts in spring will help by allowing air to circulate through the centre of the plant. This is often referred to as pruning to create an ‘open, wine-goblet’ shape.
During the flowering season, regular dead-heading of the faded blooms will help maintain good air circulation, too. In addition, removing any affected flowers will stop the secondary grey mould infection which can compound the problem. Don’t over feed plants which high-nitrogen fertilisers as this will tend to promote very soft tissue growth that is more vulnerable. High-potash fertilisers will help make petals more robust as well as encouraging plants to be more floriferous.
Some varieties of roses and other plants are more prone to flower balling than others. Where the problem is very persistent it may be worth replacing with a less-vulnerable variety. Remember that this condition is exacerbated by high rainfall, so it tends to be much more prevalent in the western side of the UK and Ireland, as well as other wet climate areas.
Frequently asked questions
What is rose balling?
It is when the petals of a bud fuse together and the flower never opens. Rain soaks between the petals, the surfaces start to break down, and a spell of sun then dries and welds them shut. It is most common on very double roses in wet seasons.
Can I save a flower that has balled?
No. Once the petals have welded together that bloom will not open, so remove it. Taking off affected flowers also stops the grey mould that often follows and would otherwise spread to healthy blooms.
How do I stop my roses balling?
Grow many-petalled varieties in an open, sunny, airy position, and prune to outward-facing buds so the centre of the bush is open and air can circulate. Deadhead through the season, and feed with a high-potash fertiliser rather than a high-nitrogen one, which only softens the petals.
Why does it happen more in some years?
Balling is driven by wet weather, especially drenching rain followed by sunshine, so it is far worse in very wet seasons and in the wetter, western parts of the UK and Ireland. Some varieties are simply more prone than others and may be worth replacing.
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