Hydrangeas are well-known flowering bushes that are fairly simple to grow as they don’t need much attention. 

You’ve likely seen them blooming in front gardens or other partially shady areas of gardens.

If you've recently decided to plant hydrangeas or are planning to grow plants near them sometime soon, you'll want to pair them with the best flowers and foliage-filled plants that will support their growth, not inhibit it. 

Thankfully, hydrangeas have more companion plants than those that threaten their well-being, so as long as you know what to avoid, it should be easy to grow these prolific bloomers without a hitch.

To assist gardeners with what plant to keep away from hydrangeas, gardening expert and CEO of GreenPal Bryan Clayton has the top four.

1. Bougainvillea 

Based on the results of numerous landscaping projects Bryan has overseen, he said: “Bougainvillea, due to its rapid and robust growth, can overpower the hydrangea, hogging space and resources.”

This negative interaction makes it “crucial” to keep these plants separate in a garden.

2. Walnut trees 

Walnut trees are definitely a non-ideal pairing for hydrangeas as they “produce a toxin called juglone, detrimental to many plants, including hydrangeas”. 

Bryan warned that the effects of this plant can “cause wilting and eventual plant death”. 

He added: “To make a point, I’ve experimented with various plant combinations, and this one is certainly to be avoided.”

3. Azaleas and rhododendrons

In his experience, the gardening expert claimed that these plants also prefer acidic soil, much like hydrangeas. 

Bryan said: “This can lead to a fierce competition for nutrients, which isn't beneficial for any of the plants involved. 

“Most people don't know this, but each plant needs adequate nutrients to flourish, making it crucial to avoid such plant pairings.”

4. Succulents

This is a bad pairing as hydrangeas love water while succulents are the complete opposite and don't. 

It's challenging to balance a watering routine that satisfies both types of plants without harming one or the other, so it’s best to avoid growing them near each other.

As well as the plants listed, those that require lots of water should be avoided as they can cause the soil to become too wet for hydrangeas, potentially “leading to root rot”.