Spring is here, and the warm conditions encourage the plants that we have in our gardens and parks to bloom and begin their annual reproduction cycle.

Plants rely on cues from climate and weather to plan their growth, bloom, and fruit. However, as the planet gets hotter due to changes in the environment and climate change, the patterns are changing.

So, how do climate changes affect our gardens? And how can we take action to combat it?

In tune with the climate

Many plants of the temperate zone developed to produce in the spring to protect themselves from damage caused by extreme heat or cold. Warmer temperatures tend to accelerate these processes, which causes plants to expand faster.

Plants have developed sophisticated methods to keep up with the climate. This makes them excellent bio-indicators of changes in temperature.

We can tell from the global assessment that the majority of plants that have been studied thus far behave as we would think they would in a climate that is warming. Research in studies in the Southern Hemisphere has found similar results.

Australia plants in the southern region of Australia tend to mature earlier in the winegrape industry; for example, they were developed by 27 days in the average time between 1999 and 2007. It is evident in the records of winemakers. You can observe from the graph below that the wine grapes tend to mature (measured in terms of their level of sugar) earlier.

The grower records winegrape maturation over time. The content of sugar (oB) can be seen as the y-axis. Notice the staple on the left in order to be able to accommodate early maturity between 2000 and 2007. Courtesy of Dr Leanne Webb

Different plants can behave differently. Apples and other fruit trees require cold temperatures to break buds out of their dormant state before beginning to grow as temperatures warm up.

That means that following warm winters such as this one, the flowering process could be delayed. The results of a new study indicate that flowering could be postponed for the Pink Lady(r) apples, as you can see below.

The timing of full bloom was observed in the Pink Lady(r) at the end of 2013. A part of the dataset Darbyshire et al. (2016)

In the above examples, Applethorpe had the warmest spring and first flowering, as we’d expect for the majority of plants. However, Manjimup was the second warmest spring and was the last to flower, even after Huon, which is the coldest spring spot. This may seem counter-intuitive. However, the reason for the delay could be because Manjimup experienced the coldest winter.

What are the implications of these changes?

The earlier appearance of reproductive tissues could increase the likelihood of devastating damage from frost. Contrary to what you can imagine, evidence shows that recent warming in southern Australia does not necessarily lead to fewer frosts. However, plants that are delayed in flowering due to warmer winters could lower their risk of frost.

The timing of flowers, whether earlier or later, could cause problems for plants that depend on pollination between various kinds. Both varieties have to shift their flowering in the same manner for the flowering times to coincide. If the flowering times do not overlap, the pollination process will not be as efficient and produce fewer fruits.

Bird and bee pollinators also need to alter their activities in line with changes to blooming times to help with pollination.

Rapid maturation could shift ripening into warmer times of the year, such as in grapes that are wine-related. This can increase the chance of extreme heat-related injury.