The glass trick for faster herbs in March

In many gardens, the end of winter still looks rather bleak. Beds are damp, nights remain cold, yet keen gardeners are already itching to get started. This is where a surprisingly straightforward tip comes in: an ordinary glass can be used to make a mini greenhouse, helping chives, parsley and other hardy herbs grow noticeably faster from as early as March – without high-tech equipment, electricity or costly specialist kit.

How the glass trick really works in March

The method seems almost too easy to be effective: simply place a glass over the young plant like a cloche. That is all there is to it. However, it relies on a small piece of physics also used by large greenhouses.

The glass creates a sheltered microclimate: warmer, more humid and free from wind – ideal for early herbs in March.

As soon as sunshine reaches the glass, the air inside becomes considerably warmer than the surrounding air. At the same time, moisture evaporates from the soil, condenses on the inside of the glass and drips back down again. This creates a warm, humid environment that encourages plants to make an earlier burst of growth.

• The air beneath the glass stays slightly warmer for longer, even after sunset.
• Wind and cold draughts cannot reach the delicate shoots.
• The soil dries out less quickly because moisture remains inside the glass.

There is just one important point: once spring temperatures become consistently warmer, or the herbs reach the base of the glass, the cloche must be removed. Otherwise, it can become too hot inside and the plants may literally scorch.

Which herbs benefit the most?

This trick is particularly suitable for hardy herbs that send up fresh growth from the ground. In other words, plants that stay in the garden throughout winter and do not freeze completely.

Chives – the perfect candidate

Chives are among the first herbs to reappear in late winter. Their fine hollow stems push through the soil early, but they are very sensitive during cold nights. Beneath a glass, chives grow:

• taller more quickly,