Should You Water in Winter?

As the days grow shorter and the temperature drops, most of us spend less time in the garden. Plants slow down, the soil stays damp longer, and it’s easy to assume watering can stop altogether. But inside your greenhouse or polytunnel, conditions are different and knowing when, or if, to water over winter can make all the difference between healthy plants and winter losses.

The Pros of Winter Watering

1. Preventing Drought Stress

Even in winter, plants in protected environments can dry out. Cold air may be damp, but it doesn’t always reach the soil beneath a polytunnel or greenhouse. Potted plants, raised beds, and grow bags dry faster than open ground, and without rainfall, they rely entirely on you.

A light, occasional watering helps roots stay hydrated and prevents stress, especially for overwintering herbs, salad leaves, and young seedlings.

2. Supporting Active Growth

If you’re growing winter crops like spinach, lettuce, pak choi, or winter herbs, they’ll still be taking up moisture, just more slowly. Keeping soil slightly moist supports steady, healthy growth and prevents the foliage from wilting during brief warm spells or sunny days.

3. Protecting Soil Biology

Beneficial soil organisms need some moisture to stay active. Bone-dry compost can harm soil life, slowing decomposition and nutrient cycling. Gentle watering helps maintain microbial health, giving your plants a stronger start when spring arrives.

The Cons of Winter Watering

1. Risk of Overwatering

The biggest danger in winter is giving too much water. Cooler temperatures and reduced light mean plants use less moisture. Overwatering can lead to:

• Waterlogged soil
  
  

• Root rot and fungal disease
  
  

• Algae or moss build-up
  
  

If in doubt, always err on the dry side.  It’s much easier to add a little water later than to dry out soggy compost.

2. Encouraging Fungal Problems

Damp, stagnant air inside a closed tunnel or greenhouse creates ideal conditions for moulds and mildew. Watering late in the day, when temperatures drop, can make things worse. Always water early, and ventilate whenever possible.

Finding the Balance

A good rule of thumb for winter watering is only water when the top few centimetres of soil are dry.

Other tips:

• Check weekly rather than watering on a schedule.  You can use the override function on your WaterMate to water on demand, rather than to a schedule.  You can also use the WaterMate as a solar powered hose.
  
  

• Water lightly and directly at the base of plants, using drippers, to avoid soaking.
  
  

• Use automation wisely — systems like the WaterMate can be set to deliver minimal, consistent moisture so soil never dries out or floods.
  
  

• Ventilate regularly on mild days to keep humidity in check.

Watering through winter isn’t about keeping soil constantly damp, it’s about maintaining gentle, even moisture so plants don’t dry out completely. The key is observation: every greenhouse behaves differently, depending on temperature, insulation, and crop type.

Whether you hand-water or use an automated system, a careful winter watering routine helps your plants survive the cold months and bounce back faster when spring returns.