It’s thirteen days since the mulberry, Morus nigra, next door sprouted its new spring leaves – in the middle of July (17.7.06). Here springtime traditionally follows Brisbane’s agricultural show – “The Ecca”, August 10 -19th.
The media always look for indicators that springs are arriving earlier due to climate change. It’s such a predictable request that I used to keep my eyes peeled at the Royal Botanic Gardens, Sydney for any early signs (or differences) from the previous year.
Climate change is a fact and the ten hottest years on record have been in the last fifteen years. Yesterday Jeff, Damien and I saw a preview of ‘An Inconvenient Truth’ (Paramount Pictures). It goes on general release in September.
The problem for food growing and natural bushland is that if a plant flowers earlier than it should (say a fruit tree) there may not be any pollinators around to fertilise flowers or to spread their seed. Natural biocontrols, like parasitoid wasps, which have evolved to exploit seasonal pests, may still be inactive or dormant when pests stoke extra early. The risk of late frosts is not guaranteed to disappear in a warming world so early flowering crops, like hazelnut, almond, cherry and peach may run the risk of flower and fruit spoilage: less food.
Climate change is one reason why growers are trying to produce fruit trees that have a low winter chill requirement. That offers some hope as winters become milder, shorter and summers become longer and hotter. Such conditions are very stressful for most fruiting trees: many orchards will find themselves in the wrong climate or fail to return a financially viable crop.
Mulberries are either dioecious (trees are male or female) or monoecious (each tree produces male and female flowers). Sometimes mulberries change from one sex to another.
Mulberries are wind pollinated, which is why they make a good bushland weed and also have some security with a changing climate. Some mulberry cultivars can set fruit without any pollination, like the Shahtoot cultivars (Morus alba var. laevigata) making them a gardener’s friend.
At least we can look forward to some mulberries in Wynnum. ‘An Inconvenient Truth’ starts screening in Brisbane from 14th September.