Former Royal gardener Jack Stooks has revealed a simple yet surprising hack that could transform your plants — and the ingredient is probably already in your cupboard.
Parul Sharma GAU audience writer
16:00, 28 Oct 2025
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Jack Stooks served at the King’s Highgrove for over two decades(Image: Archives)
Green-thumbers are constantly seeking straightforward techniques to improve their garden’s look and add vibrancy — especially tips and tricks that demand little effort or expense.
It’s well known that hydrangeas are beloved by gardening enthusiasts, as their vivid blue, purple, and pink shades can dramatically enhance a garden’s visual appeal. But how can one guarantee they’re always looking their absolute finest — and bluest?
King Charles’ former gardener Jack Stooks has revealed his unusual method to make hydrangeas more brilliantly blue than ever before.
Working alongside Coffee Friend to share his knowledge, Jack discloses that if you desire your hydrangeas to achieve a truly blue colour, you should add a spoonful of coffee during the autumn period.
He states: “Coffee is great for acid-loving plants, such as hydrangeas. If you want a really blue hydrangea in your garden, you would want to feed them these coffee grounds in the Autumn months. The coffee will be used as feed within the pots.”
Jack’s secret hack is for making your hydrangeas bluer than ever(Image: Getty)
Jack – who worked at the King’s Highgrove for more than two decades — also revealed coffee has many other uses throughout a home and garden, and can even serve as an insect repellent. He suggests positioning the common kitchen staple in bowls near your outdoor seating areas to keep those pesky mosquitoes at bay.
Although it works well to keep insects away, it also draws worms into the garden — something he says is highly beneficial. The former Royal gardener said: “Coffee grounds are also really good for bringing worms into the garden. They can be used to create air and in turn, helping the soil overall.”
It turns out your old coffee grounds could also help you save money, as they make a great alternative to costly store-bought fertilisers.
Jack advises: “Coffee grounds can be used in the garden as a fertiliser. Like most fertilisers, it consists of the elements NPK, nitrogen, phosphorus and potassium. You can sprinkle it all over the borders for home use. As you don’t tend to have too much of it, you just find an area within the border, and be selective in small areas, until all of the borders have been covered.”
The gardening expert adds: “Coffee grounds can also be used to make body scrubs, for use in the shower or the bath.”
Beyond this coffee-hack, autumn pruning proves essential for many plants, including hydrangeas, as it helps to maintain their size and shape. The aim is to remove dead, diseased, and damaged stems and enhance the plant or shrub’s appearance.
Nevertheless, one specialist cautions that trimming at the ‘incorrect’ time of year can lead to a plant that fails to bloom. Paul Parker, horticultural expert at plants and perennials specialists, J. Parker’s, explains: “When to prune hydrangeas largely depends on the type of hydrangea you have in your garden. If you aren’t sure what type is growing in your garden, I advise you to wait for them to flower in summer and prune them the following year.”
Hydrangeas are a favourite amongst gardeners in the UK(Image: Getty)
The expert recommends that shrubby hydrangeas should be trimmed in late winter or early spring. This is because the flower heads provide protection from frost for emerging buds, reports the Express.
Paul added: “Popular shrubby hydrangea varieties include mophead hydrangea, like the Hydrangea arborescens Annabelle, and shrubby lacecap hydrangea (the serrata and aspera types).
“The popular Macrophylla Hydrangeas fall into both of these, so it’s important to do your research first. However, pruning advice may differ slightly between varieties, so it is always best to check.”
Furthermore, the gardening specialist cautions: “Try to avoid pruning too much off the top of the plant, as this is where most of the flowers will appear.”
Gardening expert Ish has also shared his beginner’s guide to caring for hydrangeas during autumn. Whilst hydrangeas are robust plants and eventually become dormant in winter, you’ll want to ensure they’re properly protected from severe weather conditions.
In a viral TikTok video, Ish recommends giving the plants a thick layer of mulch. This can be done using multipurpose compost, bark chips or chopped leaves. Ish explains: “Hydrangeas may be hardy but they still can benefit from a good bit of mulching, whether you’ve got some multipurpose comport, some bark or even some shredded leaves.”
He also recommends applying the mulch directly onto the plant’s base. This will help create a protective barrier between the plant and the severe conditions during winter.
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