Why Does Rosa Rugosa Yellow at the Base?

Diseases and Pests

• Roses are particularly susceptible to fungal and viral diseases and although rugosa is very resistant to most, it can acquire an infection. Rose mosaic is a common virus in the rose family that causes yellowing of foliage in circles or patterns. The leaves eventually turn completely yellow and fall off. The virus will not kill the plant but can reduce its health. Pests like sucking insects are very drawn to rose bushes. Rosa rugosa can become infested with aphids, scale and other insects whose feeding activity will cause the foliage and even stems to fade.

Chemical Damage

• Rosa rugosa can become stressed by high applications of fertilizer, especially around the base and roots. Fertilizers can burn when applied in the wrong amounts. Granular fertilizers and soil drenches are applied at the base of the plant and splashing or grains that adhere to lower foliage will cause them to yellow. Herbicides also have an adverse affect if the foliage comes in contact with them. Ground spraying for weeds can produce overspray that gets on non-target leaves and kills them.

Heat Reflection and Stress

• Roses like to grow in hot areas and thrive in sun, but even they have sensitive leaves that can scorch. Heat reflection in rugosa is caused by watering during high light hours. Any puddling will reflect and amplify the sun's rays. Excess heat and dark mulches around the base of the rose, will cause heat stress. This can start as just wilting leaves and progress to discoloration of foliage. The heat is reflected off the mulch and ambient heat raises temperature levels beyond the plant's ability to adjust.

Cold Weather

• It is normal for rosa rugosa leaves to change color in fall. The colors are rich, deep yellows and herald the defoliating of the plant for winter. However, discolored yellow leaves in spring or other seasons may mean that the plant experienced a cold snap. Foliage returns in late winter or early spring, but it is not unheard of for hard freezes to occur even into late spring. Such extreme changes will shock the leaves, and they will change color and fall off as if it is autumn.