The oak tree’s distinctive rounded leaves and acorns make it an easily identified plant, but thereβs a hidden beauty within this tree that people often overlook: the oak flower.
Oak flowers look a little different to the bright, sweet-smelling tree blossoms found on cherry or apple trees. However, they are just as fascinating and important for our ecosystem as other spring flowers. In this post, weβll explore the different types of oak flowers, when they bloom, how theyβre pollinated, which animals eat them, and how to identify them.
Do Oak Trees Flower?
Yes, oak trees produce two types of flower: male catkins, and female pistillateΒ flowers. These flowers look different to most spring blossoms, and are a little harder to identify – especially the female flowers.
What do oak flowers look like?
Male vs female oak flower
Oaks are considered a monoecious species, as they produce both male and female flowers. The male flowers are easier to identify, as they ornamentally hang down from the tree in a cluster known as a catkin. Oak catkins are usually yellow or green in colour, and measure at around 6cm (2.36 inches) long.
These catkins have no petals, and instead have a small fringe around their base to allow for more effective wind pollination. Their elongated, hanging structure allows for their pollen grains to be dispersed by even a gentle breeze.
Female oak flowers can be found above the base of leaves and the ends of branches. Theyβre typically red or mahogany coloured and sit upon small flower stalks known as peduncles. When pollen from another oakβs catkin reaches one of these female flowers, fertilization can occur and lead to the production of an acorn.
When do oak trees flower?
Oak trees flower in late spring, between April and May. The first catkins usually appear before any leaves grow on the tree. Blooming at this time of year is advantageous as the weather has warmed enough for the flowers to be safe from freezing weather. The windy conditions of spring also allow the trees to better disperse their pollen. Once airborne, oak pollen can travel over long distances β particularly in dry conditions.
How are oak trees pollinated?
Oak trees are predominately wind pollinated. The wind carries pollen from the male flowers to the female flowers, at which point fertilization occurs.
Although there are rare instances in which oak trees self-pollinate, typically the pollen would need to come from male flowers on a different tree. On one tree, female and male oak flowers will usually mature at different times to avoid self-pollination.
Oak trees are also pollinated by insects such as bees, butterflies, moths, beetles, flies, and wasps. As insects physically carry pollen directly into the flowers, insect pollination produces better developed, higher-quality acorns.
Animals and insects that eat oak flowers
Oak trees are an important part of many ecosystems, and their flowers provide a valuable food source for many insects and animals. Although oak trees donβt produce a sweet nectar to attract pollinators, insects such as butterflies, miridae (like harpocera thoracica), and oak-mining bees feed on catkin pollen.
Oak flowers are also consumed by birds and mammals like mice, deer, and grey squirrels in early spring, as theyβre one of the earliest available abundant food sources. Of course, fertilised oak flowers will also eventually become acorns, a rich source of protein and minerals for a wide variety of animals (such as badgers, grey squirrels, woodpeckers, rats, and mice) in the cooler months.
Did you know?
One of the reasons why grey squirrels are outcompeting red squirrels in the UK is because they are able to easily digest acorns. Red squirrelsβ digestive systems are not equipped to extract adequate nutrients and calories from acorns, so they have fewer food sources to choose from.
Overall, oak flowers play a vital role in the reproductive process of oak trees. With no petals and flowers that hang from branches in long, ribbon-like strands, they have adapted to highly effective for wind pollination. The oak flower is not only crucial to the continuation of the oak species, but also an important part of many ecosystems. Many animals and insects depend upon oak flowers and acorns (oak fruit) as a source of food. We also depend upon pollinators who feed on and utilise oak pollen, such as many varieties of bees and butterflies.
This post was all about oak flowers!
