If, like me, your brain seemingly ceases to function above 25C, it’s been a tough summer. And a tough one too for our community orchards out there, surviving in the dusty earth and scorching heat only by the love and care of dedicated volunteers.
The polar jet stream increasingly fluctuating more than usual has been contributing to the extreme weather events and nine of the ten hottest years over the past century haven taken place since 2002. So in the age of the Anthropocene, is it possible to future proof an orchard against climate breakdown?
Let’s first look at the consequences that might arise:
Drier summers and drought. Less moisture available in the growing season can cause root stress, a smaller fruit size or premature fruit drop and the hotter drier summers may result in an increase in that familiar annoyance, powdery mildew (Podosphera leucotrica).
Warmer longer growing seasons. Warm and humid conditions are loved by Erwinia amylovora, aka fireblight, and wet springs could make this bacterium more widespread. Warmer summers may also increase pest populations and see new arrivals from overseas, such as the Pear Blossom Weevil (Anthonomus spilotus).
Warmer winters and fewer frosts. Frosts are wonderful for killing off insect pests, who may otherwise survive the winter, leading to higher populations and greater pressure on trees. Equally, the cold is important because each variety of fruit tree has a minimum requirement of chill hours – a period roughly of 0C to 7C – needed for vital blossom and fruit set. Fewer hours could result in blind buds or sporadic inconsistent flowering.
How can we adapt to the unpredictability? There are some practical options:
Down with the monoculture. Complexity is key, as species diversity and variety reduces an orchard’s vulnerability. It can be more resilient; supporting beneficial insects and wildlife communities and have a range of different pollination times. Check out http://www.permacultureorchard.com/ to see a five acre permaculture orchard with over 100 different apple cultivars. It’s also good to plant with the future in mind and choose known disease resistant varieties, for example the pear Pyrus communis ‘Moonglow’ for fire blight.
Less chill. Most apple trees have a chill requirement of 1000 hours, but there are varieties that have low chill requirements. Some of the lowest include “Anna” needing 300 to 400 and “Dorsett Golden” found in the Bahamas and reportedly only needing 100 hours! However, it’s worth nothing that both flower very early i.e. January/February, so there may be pollination issues.
Mulch ado about. So simple and so helpful, effective mulching helps the soil retain moisture, reduces evaporation, prevents erosion, protects plant roots from extreme temperatures, improves soil texture and controls those weeds which compete with the tree for resources. See our previous blog for more details on its wonders here: www.theorchardproject.org.uk/blog/mulch-ado-about-nothing/
Get serious about biosecurity. Have a good idea about what pests and diseases look like. Check and double check with regular monitoring. Develop contingency plans for outbreaks of new pests/diseases and other extreme events. Talk to other orchards in the area to see what they’re experiencing and remember good hygiene practices when it comes to your tools.
Consider the exotic. It may be time to think about more exotic varieties that increasingly may thrive in our climate. In London there are orchards already experimenting with kiwis, avocados and pomegranates. Pomegranates need autumn temperatures of 13C to 16C to ripen fully, but perhaps this isn’t so far off. With the changing climate could even the orchards of Kent become groves of olives?