20 Dec 2023 13:53

Greenhouse Watering in Winter

The dark winter months are upon us. If you engage in winter cultivation, you've likely noticed that plants grow slower and have different water needs compared to the summer. How much water is required? And how often?

The answer isn't simple. Watering during winter cultivation is more technically challenging than in the summer when the greenhouse constantly thirsts for water. This article aims to explain this complex subject in an easily understandable way. Invest just 5 minutes to learn about effective methods for greenhouse watering in winter.


Significant Winter Challenges

A common challenge in winter is striking the right balance with watering – providing enough but not too much. Excess water and high humidity in the greenhouse create an ideal environment for pathogenic fungi that harm our plants. Fungi, unlike plants, lack chlorophyll granules and cannot form organic connections on their own. They are classified as heterotrophic organisms, relying on pre-existing organic material, such as our greenhouse plants, for sustenance.


Spread of Fungi Pores

As a greenhouse owner, dealing with harmful fungi is inevitable. These fungi originate from the surrounding nature and spread through various means, such as wind, water, and insects. The method of spread depends on the type of fungus. For instance, mildew fungus can travel several miles through the wind. Additionally, fungi can spread when carried on seeds, onions, plant stems, or soil introduced into the greenhouse.


Infection Requires Specific Conditions

Despite exposure to numerous fungi spores, it's not guaranteed that they'll attack the plant. Precise infection conditions must be present for the fungus, with humidity being the determining factor. Most fungi thrive in high humidity environments.


Diverse Types of Fungi

In our greenhouse, there's a range of useful fungi, especially in the soil. However, our focus is on the fungi problematic for plant cultivation, which can attack the entire plant or dead plant material. Some fungi are species-specific, targeting only certain plants like cabbage. Others are obligate parasites, growing exclusively on living plant material, while some thrive solely on dead plant material, known as obligate saprophytes.


Preventing Fungi Diseases

Preventing fungi from developing on our winter-cultivated plants requires minimal effort. Maintain a clean greenhouse by removing old plant scraps, as some fungi live on decaying plant matter. Despite winter conditions, airing out the greenhouse is crucial, except during storms to prevent damage. When watering, aim to keep the plant leaves dry by using a water jug without a spreader. Dry leaves discourage fungi growth.


Determining When to Water

It's often challenging to know when a plant needs watering. For potted plants, assess the need for water by lifting the pot to feel its weight. With fixed soil beds, assess moisture content by feeling a handful of soil to check for suitable saturation.


Watering Guidelines
  • Lift pots on sunny days to assess watering needs.
  • Avoid watering on cloudy and foggy days.
  • Water jars and pots approximately twice a week.
  • Water fixed beds once a week.


Effective Fungi Prevention
  • Avoid using drip watering systems in winter.
  • Water at noon in sunlight.
  • Air out the greenhouse when possible.
  • Refrain from using a spreader while watering.
  • Cultivate various types like kale, salad, and leaf beet.
  • Keep the greenhouse clean by removing dead plant material.

Om Spirekassen

Christine Wiemann is a greenhouse grower and an agricultural technician and owner of the seed company Spirekassen. Christine is an author of several books about lifestyle, garden life and plant cultivation. Today she writes blogs and shares her knowledge and passion for greenhouses. Christine is a greenhouse expert and an ambassador for Juliana Drivhuse.

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