If you live in a zone that gets cold in winter, you need to take care of your potted plants. One of the questions you may have is if you should water the plants before a freeze.

You should water potted plants before a freeze but only if it’s a light or medium freeze that will last for a few hours or a couple of days. The moisture will help the potting soil retain heat longer and protect the plants. You should not water if it’s a hard freeze that will last the entire winter.

I’ll help you understand the different situations you may face a freeze situation in the garden and what you should and should not do when watering your potted plants.

What are the different types of freeze that can happen?

A freeze is a situation where the temperature in your garden drops to 32 degrees Fahrenheit or below. This causes freezing of the moisture in and around the plants.

Light freeze happens when the temperature drops between 29 to 32 degrees Fahrenheit. Medium freeze happens when the temperature drops between 25 to 28 degrees Fahrenheit. Hard freeze happens when the temperature drops below 24 degrees Fahrenheit.

Why should you water potted plants before a freeze?

You should water potted plants before a freeze because it helps the potting soil retain heat. The water also releases heat as it begins to freeze. This will keep the plant warm and protect it from freezing.

If the temperature drops below freezing, the water inside the plant will freeze and damage the plant tissue. When you water the potted plant it will avoid this situation as the plant will remain warm.

I took a survey of fellow gardeners who are growing plants outdoors and asked them if they watered the plants before a light freeze. 69.2% told that they did not see the need. But it is very important to water the plants as we know how beneficial it is.

Note that this will only work in case of a light or medium freeze for a few hours or days. You can’t use this to protect plants in a hard freeze that lasts the entire winter.

Most plants won’t survive this and either die or become dormant depending on the type of plants you’re growing. Annual plants will die while perennial plants may overwinter and become dormant till spring arrives.

When should you water potted plants before a freeze?

You should water the potted plants on the day you know there’s going to be a freeze due to a drop in the night temperature.

I would recommend that every morning you check the weather forecast for the next few days as part of your gardening routine.

You need to know when light or medium freeze is going to hit your region. You need to water the plants on that day before the night temperature will drop to freezing.

You should not water the potted plants if the ground has already frozen because the water will not reach deep into the potting soil. The cold will freeze it before it can percolate through the soil. It cannot have time to retain the heat in the soil.

You should also not water the potted plants if the temperature has dropped to 40 degrees or below. The potting soil is already cold and the water won’t insulate the heat inside it.

How much should you water potted plants before a freeze?

You should give the potted plants a deep watering before a freeze can arrive. This means you use a watering can to pour water till it comes out from the drainage holes at the bottom.

You need to give such a deep watering to ensure that the potting soil gets the required moisture throughout. This will help the water retain the heat in the potting soil and protect it from freeze.

Make sure that the water is at room temperature before you water the potting soil. You should avoid using cold water that will not be as effective in protecting from the freeze.

What else should you do to protect the potted plants from a freeze?

Water will help you protect your potted plants from freeze but you can do some additional things to give even more protection.

Use a mulch on the potting soil

Mulch is a layer of organic material such as dried leaves, grass clippings, straw, hay, or wood chips.

I recommend adding 2-4 inches of mulch on top of the potting soil. This will insulate the potting soil so the heat remains inside it for a longer period of time.

The mulch will also help the potting soil retain moisture for a longer time. Which helps retain the heat as well as require less frequent watering.

Use a cover on the potted plant

Once you know that frost will hit the potted plant that night, you can water the potting soil and cover the plant with a row cover.

This will help the plant retain even more heat. The potting soil will release water that will move in the upward direction and be captured by the cover.

You can use landscape fabric, cloth, towel, and netting as a row cover. Just make sure the row cover is not touching the plant as it will cause the plant to freeze.

On really chilly nights, mylar thermal blankets (aka space blankets ), with the aluminized side facing down toward the plants, helps reflect 99% of the heat back to the earth. (ruralsprout.com)

You can use a stake or poles to keep a gap between the plant and the row cover. You can place a plastic sheet or tarp on top of the row cover to give additional insulation.

Make sure to use stones or bricks to anchor the row cover on top of the potted plants so it does not fly away due to wind.

You need to remove this row cover in the morning so the potted plant can get the required sunlight and aeration.

Place painted milk jugs filled with water

You can paint milk jugs with black color and fill them with water. Place them outdoors in sunlight and they will trap heat.

You can then place these jugs together with the potted plants at night. They will release the heat they captured during the day and keep the potted plants warm.

Bring the potted plants indoors

If you have space inside your house you can bring the potted plants indoors. This could be a location such as a garage or a basement.

The location will be much warmer than the freezing weather outside. And the moisture in the potting soil will help keep the plant warm.

You can bring the potted plants back outdoors in the morning so they can get the required sunlight and aeration.

If the potted plants are heavy, it’s best to keep them on a trolley that helps to move them around with ease.