Head gardener Phoebe Hay leads the garden maintenance on the 15th floor, looking after one of London’s most distinctive rooftop gardens.

Phoebe and her colleague Shunsuke, both highly skilled gardeners, spend their time making the garden look its absolute best whilst also happily answering questions from anyone who stops to ask about a plant.’

Working together

Asked what she’s most pleased with, Phoebe doesn’t start with plants at all. “I’m very proud of the way we’ve been able to collaborate as a team to maintain and develop the garden,” she says. For her, The Garden at 120 is “the result of the joint efforts of Landform, LUC and BNP Paribas,” with regular catch‑ups to look at what’s working, what needs changing and what to try next.

As head gardener, Phoebe both plans and executes the work that needs to be done on site. It’s important to properly keep track of the large horticultural tasks that happen throughout the year, such as the seasonal wisteria pruning and box clipping, as well as the every day garden maintenance. It’s a mix of planning and hands‑on work that means the garden feels well looked after whenever people come up, on bright spring days and grey winter lunchtimes alike.

An award for horticultural excellence

In 2022, The Garden at 120 received a BALI Special Award for Horticultural Excellence, given specifically to Phoebe for her work here. It was the first time the British Association of Landscape Industries had created a special award for one individual, recognising the standard of horticulture on the roof.

Phoebe describes the award as “a huge surprise” and “very unexpected,” but also very gratifying. It showed that others value the care and hard work that we’ve put into the garden.

Biodiversity on the 15th floor

Biodiversity is now one of the main things guiding decisions in The Garden at 120. Any new or replacement planting, Phoebe says, “has to fall into one of two categories”: either British native species, or plants from the RHS “perfect for pollinators” list to encourage bees, butterflies and other insects. Over time, that simple rule has gently shifted the planting towards species that do more for wildlife while still fitting the look and feel of the space.

The garden also includes bug hotels and swift boxes, and a university group is carrying out a biodiversity study to track how life on the roof changes as the planting matures. A larger project is turning the formal water feature into a planted one, with a new filtration system so it can support aquatic plants instead of relying on chemical dosing. As those plants establish, they’ll bring extra movement and habitat into the middle of the City.

The reality of gardening in the sky

Because The Garden at 120 sits on a roof, the plants grow in a specialist, lightweight medium made mostly from crushed volcanic rock. It keeps the structure safe but doesn’t hold water and nutrients like ordinary soil, so a drip irrigation system delivers water and liquid feed every day and needs close attention in hot or windy weather.

The weather is more intense up here. “If it’s hot, it’s usually twice as hot; if it’s cold, it’s twice as cold,” is how the team describe it. Some plants thrive on that, such as hydrangeas and fruit trees like figs, apples and pears, with figs harvested for use in the restaurant below. Others, particularly the box parterres, have to be watched carefully for box moth caterpillar and box blight so any problems are caught early.

Questions Phoebe hears most

Visitors rarely run out of things to ask. “The most common questions I receive are usually about the wisteria, how it’s maintained, how we’re training it over the pergola, any problems we have with it etc,” Phoebe says. “People are also interested in how we keep the box pest and disease free. My favourite conversations are with the visitors who’ve come a long way and are eager to talk about the more unusual plants (usually the Eryngium!).”

Favourite plants and moments

“There are so many exciting moments in every season,” she explains when asked to pick one favourite. In April, the first wisteria flowering is an obvious highlight, but she also loves the point when the first narcissi appear, signalling the end of winter on the roof.

A section of the garden she finds especially beautiful is a bed with a row of lavender, Perovskia, Nepeta, Eryngium and Gaura. It has a lot of movement and texture as the weather changes.

Things you might miss

“As there are different things happening in each season, you might not see all the things the garden has to offer if you only visit once,” Phoebe says. One example is the row of Crocosmia ‘Lucifer’, which looks spectacular in summer but can only be seen at that time of year.

She also notices that many people stop at the main viewpoints and don’t always walk right around the rooftop. Those who do explore further find quieter corners, including a shadier area planted with hydrangeas and white‑flowering plants, which offers a calm place to sit slightly away from the busier edges.

The highlight of her year

“My favourite season is always spring, it’s always joy to see everything starting to grow and bloom again,” Phoebe says. It’s a very busy time in the garden, but also the most manageable weather‑wise, when it’s neither too cold nor boiling hot, both of which can be a challenge up here.

Spring brings some of the clearest changes: early narcissi, followed by tulips and alliums, and then the wisteria flowering across the pergola. Watching that cycle return each year, and seeing how people respond to it, is a big part of why she enjoys looking after The Garden at 120.