Why the climate crisis means some English roses won’t bloom anymore

Jthink of the quintessential English garden and a rose will invariably come to mind. Their sweet fragrance and fluffy petals have long been prized by gardeners, but now some of the most popular varieties are being withdrawn by growers due to deteriorating weather and pests.

Although their use in gardens is thought to have originated in China and Iraq, for hundreds of years they have been a flower of choice across England. And the undisputed king of rose growing for the past six decades has been David Austin, who died in 2018 but whose roses fill gardens across the country with their intoxicating color and scent. His company, which is still in operation, said it was going to retire some of its most popular species because they are no longer feasible to grow.

The ballet pink flowers and fruity tea scent of A Shropshire Lad, a beautiful climbing rose, has won awards from the Royal Horticultural Society (RHS) since it went on sale in 1996. With its nearly thornless stems and perfectly symmetrical petals, it became the climbing rose of choice in David Austin’s collection for those who wanted pearly pink flowers. But in recent weeks it has been withdrawn from sale.

Tim Smith, Director of Operations at David Austin Roses, said: “We cannot sit still and watch the evolution of diseases and pests as conditions and climates change, threatening the health and success of some of our most popular varieties.

“This means retrying all our releases and in some cases removing very popular strains, for example A Shropshire Lad. Although these plants may still work under certain conditions, in the long term changing conditions mean that we recommend alternative varieties that are better suited to the changing environment.

“While this is not an easy decision and will lead to a short-term drop in revenue, we must take the courageous decision to remove them.”

Another rose retired this year is the beloved and spectacular Munstead Wood, which has deep, velvety crimson petals and a classic old rose scent of blackberry and plum. Although only bred in 2007, this is a relatively new breed, it is believed that pests have ravaged it causing it to be withdrawn from sale.

Where once the primary consideration for a perfect rose was its showy blooms and beautiful fragrance, horticulturists now select for climate resilience. Rose growers are now growing flowers in countries with more arid conditions, to ensure that as the climate deteriorates as conditions change in England, they do not lose their quality. Some growers test their flowers in hot, humid regions, including Florida in the United States and Shenzhen in China.

Simon Toomer, Curator of Living Collections at Kew Gardens, said: “The roses we see in the gardens are the product of hundreds of years of plant breeding from wild species. Most of this breeding was aimed at selecting showy and reliable flowers and fragrance.

“In addition to flower quality, selection has always been influenced by resistance to diseases such as black spot and powdery mildew. As the climate has changed rapidly in recent years, especially the mild, wet springs and hot, dry summers, these diseases have become more damaging. This is partly due to the fact that roses are less adapted to new climatic conditions and therefore more susceptible to disease.

The pests also thrive in the wetter conditions brought to England by the climate emergency. Toomer explained, “Wet conditions in spring also suit the biology of the fungal pests themselves. This means that plant breeders have had to put more emphasis on disease resistance by introducing genes (through hybridization) from more disease resistant plants. It is often the wildest types of roses that have a natural resistance to disease. It also means that some strains (including some old favorites) are now too disease-prone to be viable. »

Some parts of England are unsuitable for many types of roses, according to the RHS, so some growers hybridize the flowers with climate-hardy plants, including tea. David Austin Roses recommends particularly disease-resistant plants on his website, including Dame Judi Dench, an apricot-colored rose created for the actor in 2017, and Scarborough Fair, a pale pink flower with an old-rose scent created in 2003. .

Guy Barter, the RHS’s chief horticulturist, said: “In addition to breeding for climate change, there is also the choice of plants suited to the site, so very hot and dry sites which are not well adapted now for roses will become less so. in the future and it can be expected that more tolerant plant species will be chosen. However, this will first apply to the south and east with other less affected regions. Likewise, clay-rich, moisture-retaining soils favored by roses will also be less affected. Choosing the right plant for the site will become increasingly important.

“Extreme weather makes plants much more vulnerable to disease – after this summer they have been drought stressed, for example so vulnerable to mildew and other diseases. The same would be said of a very wet summer – so climate change makes plants more vulnerable in general and extreme conditions would make certain diseases more common.

Devastated roses – pests and diseases are spreading due to the degradation of the climate

• Black spot on the rose in a wet summer can totally strip a rose bush of its leaves and is the main constraint for breeders. Breeders select resistant varieties, but over time, as fungi evolve, they become less resistant. Black spot can be treated by removing all affected leaves and plant parts, raking them up and destroying them. Next, prune the back of the rose bush with clean tools.

• Powdery mildew and rust also spoil flowering and do well in wet conditions. Destroying infected fallen leaves in the fall will reduce the amount of infectious spores next spring. Prompt pruning of infected shoots will reduce subsequent infection.

• Aphids can swarm in early hot summer. They peak in June before the ladybugs can fully help control their population. The RHS recommends using the finger and thumb to crush aphid colonies where possible and to encourage predatory insects.