What are blind shoots?

August is the month when we finish our winter prune and the first signs of new seasons growth are seen as temperatures start to warm up. It is one of my favourite times seeing the roses shoot away into growth with the promise of blooms in months to come.

It can also be frustrating at times, particularly in a cooler, wetter spring when blind shoots can occur on our roses. This is where a shoot fails to produce a flower, either by failing to produce a flower or aborting it after development has started. Their development is mainly caused by low light levels and to a lesser degree by cooler temperatures.

The process which leads to the development of blind shoots is rather complicated but the following explanation I have tried to make as simple as possible.

Light and temperature are two of the factors that influence the rate of photosynthesis in plants that is the conversion of light energy (i.e. sunlight) to chemical energy which in the plants case are carbohydrates. These are produced in the leaves (source) and are exported to other parts of the plant for growth and reproduction; such as roots, shoots and flowers (called sinks in the plant science world).

Low light levels limit the rate of photosynthesis, leading to increasing competition between the developing flower and vegetation for carbohydrates. The developing flower is a poor competitor compared to vegetative growth for carbohydrates and it is this shortage that leads to blind shoots developing.

There appears to be some genetic basis to blind shoots with some types of roses more susceptible than others. In my limited experience, I have observed that Hybrid Teas seem to develop the most blind shorts while the old fashioned and climbers develop the least and floribundas and miniature type roses fall somewhere in between. There is also variation in between varieties of the same type.

Blind shoots are frustrating at times but there is not a lot you can do about them unless you want to grow your roses in an expensive glasshouse. Most blind shoots will come away into growth again under their own steam so there is generally no need to go around and pinch the tips out.

I would like to make two suggestions that you might like to think about, and are simple yet are practical.

1. Grow your roses with as much exposure to sun as possible, particularly during spring as this is when the roses are growing yet we also experience quite a few overcast days. Avoid planting roses to close to each other and also other plants, any shading will magnify the effect of low light levels.
2. The other thing you might like to try is match the type of rose to different situations in your garden. Plant those types (like Hybrid Teas based on my experience) in the sunniest situations and save those that don’t seem to get many blind shoots for less sunnier positions (like climbers and old fashioned types).

Check out the rose of the month – Fireball

In the Rose Garden for August

• Continue to prune roses which should be done by mid month.
• Once pruning is done, tidy up around the roses, pick up any fallen leaves, remove weeds and lightly fork over the ground.
• Apply a winter clean up spray of copper but leave it until a few days after pruning.
• Check stakes and ties on standard roses and renew if required.
• Towards the end of the month and into September, apply a general rose fertiliser such as Neutrog’s ‘Sudden Impact for Roses’ to your roses at the recommended rates.

By Hayden Foulds

Hayden also serves as Deputy Chairman of the World Federation of Rose Societies Rose Trials Committee amongst other rose endeavors. 

Read more from Hayden here.