Are the leaves on your roses turning yellow? Discover the causes and find the right remedies
Considered a symbol of passion, love, elegance and beauty, roses are amongst the most beloved of flowers and are widely cultivated in gardens and on terraces. But roses are not impervious to the elements and even the most experienced gardeners may find the leaves of their roses turning yellow.
There are various causes of this yellowing and discovering the right one is a vital first step to dealing with the problem. Below, we outline the possible causes of yellowing rose leaves and how to deal with this.
1. Water
Poor watering habits are the main cause of yellowing rose leaves:
- Too little water: your roses will start to wilt if you have not given them enough water (or there has been an excessively dry period - in which case, the leaves turn brown on the edges). Solve this problem by increasing the frequency of your watering and immersing potted roses in water for 10-15 minutes. Add a thick layer of mulch to limit moisture evaporation.
- Over-watering: over-watering will cause excess moisture to stagnate, leading to root rot; additionally, sodden soil makes it difficult for the plant to extract the nutrients it needs. Solve this problem by watering your roses thoroughly, but only when the surface layer of the soil has dried out. If rainfall is causing this problem, increase the drainage properties of the soil by adding organic compost, aged manure or shredded bark.
2. Light and heat
Lighting and temperature conditions can be possible causes of yellowing:
- Roses need 6-8 hours of direct sunlight each day and poor lighting could easily cause yellowing of the leaves. If the bush is too thick/dense, the yellowing will be found on the lower branches. Move your rose to a sunnier place or prune the bush to illuminate the lower limbs;
- Extreme temperatures can also damage your roses. A temperature above 30 degrees C for extended periods could cause the yellowing of the leaves. Protect your rose during the hottest part of the day by placing it in a sheltered spot or using shade cloths.
3. Leaf diseases
- Black spot blight is a disease caused by the fungus Diplocarpon rosae which causes the appearance of dark or black spots surrounded by yellow "halos" and quickly spreads to other parts of the plant (and possibly also to nearby plants);
- Rose mosaic disease, on the other hand, is a virus that causes leaves to turn a bright, mottled yellow with zigzag, speckled or spiral spots, and stops roses from growing and flowering.
Both these diseases are incurable, but you can easily save your rose by cutting off the affected leaves and preventing the spread of spores by spraying the leaves with a baking soda solution.
4. Nutritional imbalances
Finally, nutritional imbalances can easily cause yellowing:
- Nitrogen deficiency manifests itself in the rose putting out yellow-green leaves that start appearing from the bottom of the plant;
- Chlorosis is caused by an iron deficiency or excessive alkalinity of the soil and causes leaves to turn light yellow, spreading from the top of the plant;
- Over-fertilization can suppress the activity of beneficial bacteria in the soil, causing yellowing of the leaves (and especially in young leaves).
Carry out a soil test to check whether the problem is acidity or nutrient deficiency, and make adjustments using the appropriate product: chelated iron (for an iron deficiency); coffee grounds (for a nitrogen deficiency) or organic compost (to balance out acidity).
As for fertilizing, avoid using a commercial fertilizer for young roses and rather use organic compounds, administered during the flowering period.
With these tips, your roses will always be at their best!