[James Kilkelly, was GPI.]

Tree leafing stages, can they forecast weather in Ireland?
by GPI

Gardeners and farmers are famous for their ability to turn their hand to any skill that is even vaguely associated with their own. For example, a understanding of the internal combustion engine can be useful when your mower or tractor decides to let you down, or perhaps it will be your working knowledge of Latin which will come to your aid when choosing between two different Latin named plant types. Say you require a shrub for planting beneath a window, remembering that “nana” is the Latin for dwarf will prevent you planting Berberis thunbergii “Atropurpurea” (6ft), instead allowing you to plant Berberis thunbergii 'Atropurpurea Nana', a tidy plant three feet tall.

Phenology is one branch of science that most gardeners and farmers have a great interest in, without even consciously knowing that they are taking part in a scientific study. Phenology is studied by a phenologist, one who records natural cycles, such the coming and going of birds and animals, and the arrival of first and last frosts.

But it is the date that leaves and flowers emerge on plants and more especially trees that is top of the amateur phenologists “must see” list. This is down to weather-lore, old sayings that claim that the leafing or blossoming of plants at certain times is an indication of the coming weather.

The weather lore saying that I hear quoted most regularly is “Oak before Ash, in for a splash, Ash before Oak, in for a soak”. This suggests that if the leaves on the ash tree appear first, it will be a wet summer, but if the oak comes first, we will receive a dry summer.

. Quercus petraea (Sessile oak) tree, leaf and acorn, photo / picture / image.

. Fraxinus excelsior (Ash) tree,leaf and seed, photo / picture / image.

Oaks and ashes are always among the last trees to burst into leaf each spring, due to the fact they cannot break bud until after the first new wood is formed. Being closer to the summer maybe these trees have some way of predicting the weather during June, July, and August, however two major question marks have been raised over their weather forecasting ability.

1. Science and records.
In 1998, the ash did arrive into leaf first, and yes, there was a lot of rain, aka a soak. But in 2001, the ash also came into leaf before the oak, but the summer was relatively dry. There are numerous examples of this sort of result shown in historical data collected from Norfolk (1750-1958) by the national trust, where there were 158 years when both ash and oak were recorded.

On 46 occasions (30%), ash was earlier, but 30% of the summers were not overly wet. The commonly held scientific theory is that the trees leaves are influenced by the spring temperatures, with oak getting more advantage over ash in warmer springs.

2. Regional variations.
Strangely, our Irish saying “Oak before Ash, in for a splash, Ash before Oak, in for a soak”, seems to totally conflict with those from other European countries. Take for example the German saying, "Grünt die Eiche vor der Esche, hält der Sommer große Wäsche, Grünt die Esche vor der Eiche, hält der Sommer große Bleiche".

This literally translated means “greens the oak tree before the ash holds the summer big washing, greens the ash before the oak tree holds the summer big bleaching”. The saying tells us the exact opposite to our saying. A Norwegian oak/ash saying also states the opposite, so it makes me wonder, if our saying is perhaps less than reliable.

Whatever you believe, don’t let this debunking prevent you from watching out for the race between the oak and ash leaves from mid-April onwards. It’s a bit of fun, so here’s hoping that the oak trees win this year!


If you are reading this article and thinking to yourself, "Hmmm, I feel I am a budding phenologist, as I have interest the chronology of leaf emergance on the different tree varieties. What you are really trying to say is that you would like to see a piece detailing the rough order that our trees leaf up each spring in Ireland.

So below find a guide to when some of our most common trees achieve their first leaf fully open. Technically the first leaf should be fully open, and recognisable in shape, if not the full size of the adult leaf.

Even though some of the plants show the same times, they are shown in their common succession.
If you wish you can click on the plant names to access further information.

Common trees as they leaf in spring

Blackthorn Mid February

Elder Early to mid-March

Hawthorn Mid to late March

Hazel Late March

Willow Late March

Horse chestnut Early April

Silver birch Early to mid-April

Crab apple Early to mid-April

Alder Early to mid-April

Rowan Early to mid-April

Field maple Mid-April

Beech Mid-April

Oak (pedunculate) Mid to late April

Oak (sessile) Late April

Ash Early may


Any queries or comments on tree leafing stages in spring, please post below.