The answer to 'garden yellowing' is that it is often caused by nutrient deficiencies, overwatering, or disease. The leaves of the plants may start to turn yellow, wilt, or drop off. To fix this, you'll need to identify the underlying cause and take appropriate action.
If the yellowing is due to a nutrient deficiency, you can apply a balanced fertilizer or compost to the soil. Overwatering can lead to root rot, so you'll need to adjust your watering schedule. Diseases like fungal infections or pests may also cause yellowing, which may require treating with fungicides or insecticides. If the problem persists or you're unsure of the cause, it's best to consult a professional landscaper or horticulturist.