These plants are already preparing for next spring

Beneath a few withered leaves, you catch a glimpse of something blue. A flower stretches towards the light with a determination that is almost enviable.

Flowers don’t procrastinate. They arrive when the time is right, and now they are here.

In fact, they have never really been gone. The plants have simply not been above ground.

"Many spring flowers prepare for spring as early as the previous year. Over the summer and autumn, they store nutrients in their stems and tubers, which lie well hidden underground. And then they shoot up rapidly, flowering and setting seed within a matter of weeks," says Malene Østreng Nygård.

She is a botanist at the University of Agder’s Natural History Museum and Botanical Garden. She knows a thing or two about what plants are up to, whether above or below ground.

“The flower buds of European thimbleweed and common hepatica lie folded up underground, just waiting for light and the right amount of warmth in the spring,” she says.

The flower’s bud lies hidden for about six months, almost like a secret gift. It only opens in spring.

It pays to be early

Spring arrived late in Kristiansand this year. In April, daytime temperatures were only four or five degrees, and the flowers were slow to bloom.

But now they’re out, having followed the same procedure as last year, the year before, and every year before that: growing and setting seed before the trees produce leaves.

“The reason hepatica, thimbleweed, and lesser celandine push their way up as early as March and April, and sometimes as early as February, is all about survival. It’s a matter of getting out while there’s still sunlight on the forest floor,” says Nygård.

The trees will soon take over. When downy birch, common hazel, ash, and Norwegian maple burst into leaf, they cast a shadow over everything growing on the forest floor. By then, it's too late for the flowers.

They must have had time to bloom, attract bumblebees, flies, and other insects, and set seed whilst there is still enough light on the forest floor.

“Things have to happen in the right order in nature for all creatures to thrive. That’s why it’s important that the trees wait to put out their leaves,” says Nygård.

Common hepatica is demanding and tough

Common hepatica is the most fussy of the three. It doesn’t grow just anywhere – it requires soil rich in lime. In return, it is a veteran.

“A single clump can live for up to 60 years, and it reappears in the same spot year after year,” says Nygård.

Ants play a key role

The seeds are spread with the help of ants. Each seed has a small oil sac attached to it. This oil is a delicacy for the red wood ant. It eats the oil and deposits the seed elsewhere.

In this way, the red wood ant helps to spread common hepaticas across the landscape.

Common hepatica flowers for just a few weeks. It grows in a round, compact tuft that is easy to spot in the countryside. It tends to grow in dark, lime-rich soil amongst last year’s dead leaves, brightening up the forest floor with its blue flowers.

“Common hepatica has its own dark green leaves that overwinter under the snow. This allows it to photosynthesise and produce nutrients as soon as the snow has melted,” says Nygård.

European thimbleweed spreads out

European thimbleweed is different. Whereas common hepatica grows in tufts, thimbleweed spreads out in carpets. It forms large, white patches of flowers.

But what you think are hundreds of separate flowers is actually just a single plant, a single individual.

“Beneath the ground lies a horizontal stem, just five to ten centimetres deep in the soil. It doesn’t grow downwards, but outwards. The thimbleweed flowers you see above ground all belong to this single stem,” says Nygård.

The underground stem distributes nutrients to all the flowers in the field.

The flowers and the bees

The European thimbleweed's stem survives all year round and stores nutrients throughout the summer and autumn. In winter, it goes into dormancy. As soon as the snow melts and the temperature rises, flowers are ready to sprout from the stem almost immediately.

“The nutrients stored in the stem are used to produce many flowers and leaves, which shoot up rapidly from the ground,” says Nygård.

The flower of the European thimbleweed is shaped like a small dish that collects sunlight. It turns towards the sun throughout the day. This large dish is an open invitation to all bumblebees, flies, and insects that come to feed on pollen.

The pollen is spread when the insect visits the next flower. After the pollen is transferred to the stigma, it grows into the egg cell inside the flower, where fertilisation takes place. The fertilised flower develops into fruit containing seeds. In the case of European thimbleweed, this looks like a spiky ball at the top of the flower stalk.

“Pollination happens unintentionally on the part of the insects. They’re really just out for food, and along the way pollen gets stuck to their bodies, which is transferred when they visit the next food source,” says the botanist.

Teaming up with the red wood ant

When the seed is ripe, the stem bends towards the ground and drops it. Then the red wood ant takes over and carries the seed away.

‘The seed contains the blueprint for a new flower,’ as André Bjerke once wrote.

“European thimbleweed also lures the red wood ant with oil. This tasty treat entices the ant to carry the seed away, eat the oil, and leave the seed somewhere else. European thimbleweed does not have a separate oil sac, but the surface of the seed itself contains oil that the ant eats,” says the botanist.

She emphasises that it's best if the ant manages to get out of the thimbleweed's patch before it eats and leaves the seed behind.

“If the seed lands in the mother plant’s area, it will compete with the European thimbleweed that is already established there, and the new seed will usually lose that battle,” says Nygård.

The lesser celandine clones itself

The lesser celandine has a different strategy for spreading, explains Nygård. It cannot produce viable seeds. The Norwegian summer is simply too short and cool for the seeds to have time to mature.

“Instead, the plant forms small gemmas in the corners of its leaves. A gemma is a kind of wart or bud that falls off easily. They detach, fall to the ground, and take root as new, independent plants,” says Nygård.

The result is large fields of lesser celandine that have cloned themselves, where all the plants are genetically identical. The yellow flowers are rich in both pollen and nectar for hungry bumblebees that are about to start a new spring season.

An open buffet for bumblebees and other insects

“All three of these plants thrive because they work in harmony with their surroundings. They provide food for the insects and, in return, receive help in transporting pollen between the flowers, which is essential for the formation of seeds and new plants,” says Nygård.

The early pollinators – bumblebees, bees, hoverflies, and beetles – are entirely dependent on something flowering as early as March and April.

Bumblebee queens wake from their winter hibernation around the same time as the first spring flowers appear. They then need nectar or pollen to survive and start new colonies.

Without the early flowers, there are no bumblebees. Without bumblebees, there is no pollination. Without pollination, there are no new flowers.

“The flowers feed the insects so that they can breed and return to pollinate the flowers again next year,” says Nygård.

The plants probably do not dream. They do not think ahead. But they are preparing for next year. They are already on track.

———

Read the Norwegian version of this article on forskning.no

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