In the white season it can get quite cold in our latitudes. How do plants survive in winter and do they photosynthesize during the cold months?
Animals grow a thick coat in winter, gorge themselves on an insulating layer of fat in summer and fall, hibernate or hibernate. We humans put on warm clothes, drink tea or try to keep warm in other ways. After all, we are warm creatures that need a specific temperature to survive. Plants, on the other hand, are cold-blooded organisms. They have developed ingenious strategies to survive the cold winter.
Wintering Strategies of Plants
The overwintering strategies of plants can be classified into different methods. In general, it is always about creating an energy store and protecting the meristem - i.e. the formation tissue of the buds, which serves as the starting point for budding in spring. There are 4 strategies:
Overwintering plants as seeds
Seed plants whose bodies are scheduled to die off in winter only survive thanks to their seeds. It contains both storage substances and the embryonic stem tissue, i.e. the meristem, with the help of which new life is possible.
Overwintering perennials: Retreat to storage organs
Perennials are perennial, herbaceous plants that survive for several years, including the winter. They shift energy-rich storage substances into the roots, alternatively into bulbs, tubers or rhizomes. The meristematic tissue is found very close to the soil surface in the form of buds or inconspicuous dormant eyes.
Wintering of deciduous trees and shrubs: Retreat to the wood
The fact that deciduous trees do not store energy in their leaves but in their wood is clearly recognizable from their autumn colours. The foliage turns yellow because energy-rich substances are recycled and transported into the woody part via the petiole. The buds for re-sprout are on treesshielded under bud scales, but often several meters above the ground and must be protected from the tree by further frost protection measures.
Wintering of evergreen plants: frost protection of leaf and bud
Evergreen plants do not shed their leaves. They therefore also shift fewer reserve substances into the wood body, instead they have to adapt their leaves to the cold weather through their structure and the storage of various substances. The buds hibernate in a state of dormancy brought about by a special cocktail of hormones.
Do plants photosynthesize in winter?
Not all plants photosynthesize in winter, but evergreens do - albeit to a lesser extent.
To answer the question in more detail, it makes sense to take a quick look at photosynthesis itself. Photosynthesis describes the process of producing organic material, i.e. building blocks for the plant body, with the help of light energy and inorganic compounds. The main role in this process is played by green chlorophyll. Plants that shed their green parts or let them die off in winter cannot carry out photosynthesis until the green plant parts are available again.
Evergreen plants, on the other hand, are able to gain energy from sunlight all year round. However, the sunlight in our latitudes is weaker in winter and only available for a shorter time. Coupled with cold, which inhibits photosynthesis, this results in only a very low photosynthesis performance. Therefore, even evergreen plants do not continue to grow in winter, but can only cover their daily energy requirements to maintain frost hardiness.
This is what plants do before winter
Preparations for the cold season begin early. Because overnight, no plant is prepared for sub-zero temperatures and diet. The cold and shorter days adjust their hormone balance in such a way that the plants gradually go into hibernation. What sounds like a break is initially associated with a lot more work than you can see from the outside. These processes take time and shouldn't be disturbed: by pruning, overwatering or fertilizing with the wrong nutrients, we can hamper the plants' preparations, jeopardizing winter hardiness.
ThisSteps plants need to perform before winter:
Storage of reserve materials
As described above, plants store their energy reserves in different places. Plants have a lot of work to do in the fall to transfer them to the appropriate plant organs.
Retreat into the wood
Leaf discoloration can be observed in autumn on most of our local deciduous trees. This phenomenon occurs because the chlorophyll - which makes the leaves appear green - is recycled and carried away. Other high-energy material is also transferred from the leaves to the trunk.
Below the bark, water-rich cell organelles, the vacuoles, divide. A few large vacuoles give rise to numerous small ones. Above all, sugar accumulates in them, but also proteins and other dissolved substances. Essential elements such as potassium, magnesium and phosphorus are also removed from the leaves before they are dropped.
Starch is stored in the amyloplasts as an energy reserve. In the course of the year, the trees draw on these reserves, so that they are largely used up again in May when the leaves unfold.
After all the important nutrients and minerals have been stored, the leaves are shed. This keeps the area for snow loads and crown movements, which can lead to fractures, to a minimum.
Trees may appear inactive on the outside in winter, but they are constantly engaged in cellular respiration. In this way they provide energy for the operation of vital metabolic processes.
Retreat into the earth: tubers, bulbs, rhizomes and roots
Many herbaceous plants such as lily of the valley (Convallaria majalis), common ground elder (Aegopodium podagraria) or ginger ( Zingiber officinale) form so-called rhizomes. It is a shoot system that grows below or just above the ground with the task of storing reserve substances. Thanks to these stored substances, including starch in particular, many plants can overwinter in the soil. Onion plants use transformed leaves as storage organs. Below the surface of the earth, these storage organs are largely protected from frost.
Plants that hibernate underground appreciate our help! Mulch can be applied to reinforce an insulating protective layer. Our Plantura organic pine bark not only protects against drying out, but also suppresses weed growth.
Retreat to seeds: propagation and winter protection in one
Plants can also overwinter as seeds. These usually consist of the seed coat, a nutritive tissue and the embryo, which can be at different stages of development. Depending on the type of seed, the nutritive tissue is of a different nature. Seeds of legumes such as beans (Vicia), peas (Pisum) and lentils (Lens) are high in protein . The seeds of cereals such as wheat (Triticum) or oats (Avena) and deciduous trees such as oak (Quercus ) and sweet chestnut (Castanea) store energy mainly in the form of starch. Some seeds, such as hazelnut (Corylus) and walnut (Juglans), form seeds with fat as storage bodies. No wonder we humans use many of these seeds for food. In seeds, too, the nutritive tissue is not only used for the step into life, i.e. germination, but also for greatly reduced cell respiration. So each seed is a living, breathing embryo. Due to a very low water content, the hard seed coat and the high concentration of osmotically active substances, it is well protected from freezing.
Autumn color of the leaves
Also independent of the fact that the yellow autumn color develops as a result of the relocation of chlorophyll from the leaves to protected parts of the plant, leaves are coloured. You can see that from the fact that some evergreen shrubs, for example mahonia (Mahonia), turn their foliage colorful in autumn. Responsible are anthocyanins and carotenoids, which are formed to protect against frost and too much sunlight. Because evergreen plants have a problem in winter: if it is very cold at the same time, but the sun is shining, a lot of high-energy radiation hits the leaf. However, cold slows down all processes in the plant cell, so that the solar energy cannot be stored in a usable form. A harmful excess of energy is created that can damage cell components - similar to when we get sunburn. The anthocyanins, which appear red or violet to us, protect against these harmful effects.
You can find a detailed explanation of leaf coloring in autumnin our special article.
Plants produce their own antifreeze
Why don't plants just freeze in winter, like vegetables in the freezer? Why can the lawn be walked on even in frost without the blades breaking like ice needles? Freezing the cell would be fatal because the water would expand and would simply burst the cells.
The answer can be explained using the example of the sea. If water is enriched with a sufficiently high concentration of osmotically active substances, its freezing point is reduced. In the sea, this osmotically active substance is s alt. Various sugars, alcohol compounds and, crucially, potassium, act as antifreeze agents in plant cells.
Tip: This is also the reason for autumn fertilization such as autumn lawn fertilization. Special fertilizers such as our Plantura organic autumn lawn fertilizer promote the winter hardiness of the lawn instead of endangering it. They do this by introducing potassium, which is stored in the vacuoles as an antifreeze.
In the leaves of common ivy (Hedera helix), for example, the freezing point can be reduced to -3 °C by storing sugar. Other molecules that prevent the formation of ice crystals in the cells also contribute to this.
Thanks to these special precautions in the storage organs, plants can withstand temperatures below -45 °C. Of course, this doesn't apply to every type of plant, but depends on where it comes from and what antifreeze precautions are built into its genetics.
Tip: We present the 10 best evergreen plants in a separate article.
Protected buds: starting point for new life
Leaf and flower buds are often established in the previous year and then enter a dormant phase to await winter. The signal for this is given by low temperatures and a short day length. Processes are now initiated via hormones in order to protect the leaf and flower buds. For this purpose they are surrounded by bud scales. Inside these scales, a white fur of dead hair forms, which has an insulating effect. Of course, “antifreeze” is also stored. In this state, the buds defy cold and frost. Only whenAs the days get longer and warmer again, the frost hardness is reduced, the water content increases and the tissue develops further. At this stage the buds are then at high risk of being damaged by late frosts.
It is warmest on the ground: geophytes such as spring bloomers hide their buds in the ground. Hemicryptophytes, which include most perennials, at least hide their buds under insulating foliage. Plants that have their renewal tissue at a height of up to 30 cm are called chamaephytes. Their buds are protected by the snow cover. If the buds are even higher, one speaks of phanerophytes, which include all woody plants. The higher, i.e. more exposed to the wind, the buds are, the more effectively they must be protected from frost.
Tip: In spring, plants can sprout prematurely with the help of fertilization and watering as well as placing them in a warm place. This is the ideal time for repotting pot and house plants and adding fertilizer for a successful start to the new growing season! Thanks to its NK ratio of 3-4, our Plantura organic indoor & green plant fertilizer is ideal for most indoor plants. But caution is advised: With this treatment we are provoking a reduction in winter hardiness, so the driven plants should be protected from frost.
As you can see, there are ingenious tactics for how trees overwinter and how other plants survive the winter. But by no means all of them are well protected against the icy temperatures. That's why we give you tips on how to overwinter your plants properly.