Both dahlias and sunflowers are tall plants that require full sun. Planting them close together can result in competition for light, which may affect their growth and blooming.
Dahlias thrive in well-drained, slightly acidic soil, while sunflowers prefer slightly alkaline soil. Planting them together can lead to conflicting soil requirements and nutrient imbalances.
Sunflowers have deep, aggressive root systems that can outcompete the shallower roots of dahlias. This competition can limit access to nutrients and water for the dahlias.
Dahlias and sunflowers have different spacing needs. Dahlias need more room for their tuberous roots, while sunflowers can grow quite large, leading to potential overcrowding if planted together.
Sunflowers attract pests like aphids and beetles, which can also target dahlias. Planting them side by side can make it easier for pests to spread from one plant to the other.
Both plants can be susceptible to different diseases. Close proximity increases the risk of disease transmission between dahlias and sunflowers, potentially affecting both plants.
Tall sunflowers may overshadow dahlias, which can lead to support issues. Dahlias, being shorter, might not get enough light if overshadowed, while sunflowers may need additional staking to stay upright.
Dahlias generally need more frequent watering compared to sunflowers, which are more drought-tolerant. This difference in water requirements can complicate watering routines and affect plant health.