Companion planting is a popular method used by gardeners to grow certain plants close together for mutual benefit. Some plants can help others thrive by repelling pests, improving flavour, or boosting growth. But the opposite is also true and certain combinations can do more harm than good.
One pairing to avoid is rhubarb and cucumber. According to gardening website The Homesteading RD, these two plants should never be planted side by side, as they can compete for space and nutrients and make each other more vulnerable to pests and disease.
Rhubarb is a hardy perennial vegetable that likes to stay in the same spot for many years, developing strong roots and large leaves.
Cucumbers, on the other hand, are fast-growing annuals that need plenty of water and can spread quickly across a garden bed.
Planting them together may seem harmless, but experts say it can cause problems.
They explained that cucumber plants are prone to powdery mildew, a fungal disease that can easily spread to nearby rhubarb, especially when the plants are overcrowded or have poor airflow.
It can also work the other way. Rhubarb leaves contain oxalic acid, which helps the plant naturally resist pests and disease.
But this chemical could affect nearby cucumber roots, potentially stunting their growth or causing issues with development.
Cucumbers are better suited to growing alongside beans, peas, corn or radishes.
These plants don’t compete as much for space and offer natural support or pest control benefits.
Rhubarb, meanwhile, does well near brassicas such as cabbage and broccoli, as well as herbs like chives and thyme.
It’s also important to avoid planting rhubarb near sunflowers, melons, or pumpkins, all of which can crowd the plant and create growing conditions that increase the risk of rot.
When planning a vegetable garden, experts recommend grouping plants that have similar growing needs and leaving enough space between crops to allow for airflow.
Keeping track of which combinations work well, and which ones don’t, can help improve harvests and reduce the need for pest control.