Marigolds are annual plants that are extremely susceptible to even a light frost. To protect them from cold snaps, you first want to ensure they have a warm, protected planting site. You should also water your marigolds to maintain moist soil, which helps avoid soil freeze. Once these are accomplished, provide various anti-frost elements to protect your plant. These include heat lamps, propylene covering, a frost blanket, heat mats, and organic mulch. If none of these techniques are adequate, consider growing these delicate plants indoors instead.
5 Methods to Protect Marigolds from Frost
While spring frosts and cold temperatures can ruin your marigolds, there are protective options. Below, we’ll get into the most common options and how well they work:
Cover the Plant
Providing propylene covering for your marigold plants is a great way to stave off frost damage. This can either be row covers or covers for each individual plant. If you can’t find a propylene cover, a standard plastic sheet or even bed sheets can work nearly as well. The goal is the same either way: to loosely drape the cover over your garden plants. Prop the sheet up with wooden stakes and then secure the cover to the ground using more stakes or zip ties.
- Loosely draped propylene covers help insulate frost-tender plants.
- Prop up the cover with stakes and then secure the drape to the ground with more stakes or zip ties.
While covering your marigolds does offer great protection for plants, it shouldn’t be used constantly. Too much reliance on propylene covering can stunt marigold growth. It’s best to limit cover use to solely when colder temperatures are certain.
Add Heat to Outdoor Plants
There are various tricks that marigold gardeners use to provide additional heat to protect marigold seeds and plants. One option is to use a heat mat to raise the soil temperature around the plant roots. Another is to provide heat lamps or even just a simple lightbulb to add heat.
- Heat lamps or heat mats can help maintain a warm soil temperature.
- Combine these elements with a plant covering for maximum effectiveness.
To heat your plants without using electricity, place a warm jug under the plant cover. This provides hours of radiating warmth that is trapped by the cover. It’s important that the water is warm and not boiling. Boiling water actually freezes more quickly than warm water.
Bring Potted Plants Indoors
Garden marigolds are especially vulnerable to frost but indoor pot marigolds are safe all year. This can vary from growing them inside at all times to just bringing them in during cold nights. Indoor plants are easy to monitor and protect.
- If possible, bring marigold plants inside.
- The inside of your home will ward off the coldest temperatures.
- You can place your plant in a home, garage, garden shed, or another area as long as the ambient temperature consistently stays above freezing.
A potted plant can be moved into another location of your house. Just make sure that the area it is moved to maintains a higher than freezing ambient temperature.
Watering just before a frost can be beneficial to plants. The key is to water your marigolds to the right level of soil moisture. Moist soil is less likely to freeze than other soil. Both dry conditions and wet conditions lead to easier frost damage. This is important because frozen soil can damage plant roots, which could be deadly to the plant.
- Water your marigolds when frost is in the forecast.
- Moist soil helps prevent frost from destroying your marigolds’ roots.
- Track soil moisture with a moisture meter to ensure you maintain moist soil.
Be sure to use a moisture meter to monitor that you are getting the soil to moist levels. Use this moisture meter to take all the guesswork out of reaching the right moisture level.
Adding mulch in the fall or winter helps shield plant roots from frost in cold climates. Mulch insulates the soil against drastic temperature changes, which can prevent frozen roots. For the best results insulating the soil, use an organic mulch made from wood chips, shredded leaves, or straw.
- Add 3–4 inches (7.5–10 cm) of mulch to insulate plant roots from frost damage.
- The best mulches for soil insulation are made of organic materials such as bark, wood, leaves, or straw.
- Mulch also helps retain soil moisture, which prevents frozen ground.
Mulch also helps retain soil moisture. So, your pre-frost watering will be more effective if you have a 3–4-inch (7.5–10 cm) layer of mulch at the base of the plant. Just make sure not to bury marigold stalks and stems in mulch, since trapped moisture could damage the plant.
Does Frost Hurt Marigolds?
Cold weather is a major killer of all marigolds, especially French marigolds. Even a light frost can easily devastate your marigold garden. This is especially dangerous in late spring when a sudden frost can catch you off guard if you aren’t paying close attention to the weather.
- It’s close to impossible to save frost-damaged marigolds.
- If the roots are damaged by frozen ground, you can’t save marigolds.
- Be attentive to weather changes and protect marigolds before they get damaged.
Because frosty weather causes heavy and irreversible damage, it’s nearly impossible to save marigolds after a frost. The only way to protect marigolds from severe damage is to protect them before the frost damage sets in.
When Should You Protect Marigolds from Frost?
When growing annual marigolds, it’s essential to protect your plants in spring, shortly after planting. This time of year has a high frost risk. So, it’s best to closely watch the weather forecast for frost until the danger of frost has completely passed.
- Protect annual marigolds from spring frost by monitoring the weather after planting.
- Perennial marigolds require frost protection in spring and fall.
- If you are growing annual marigolds, you don’t have to be concerned about fall frost—your annual marigolds will die naturally at the end of fall.
When growing perennial marigolds, watch for frost in spring and fall. If you live in a region with cold winters, make sure to bring perennial marigolds indoors, since a deep freeze will kill them. You don’t have to be concerned with protecting annual marigolds in the fall. Annuals will die naturally in the fall. Then, new marigolds will sprout from seed the following spring.
How to Cover Marigolds from Frost
Protecting marigolds from winter and spring frosts is essential to keeping your flowers alive. Here are a few tips for protecting your marigolds from frost:
- Protect marigolds with plastic frost covers before nighttime frost arrives.
- Heating elements—such as mats and lamps—can warm the soil around marigolds and prevent frost damage.
- Water your marigolds before frosty nights to prevent the soil from freezing.
- Add a layer of mulch around marigolds to insulate plant roots and maintain soil moisture.
- Bring your marigolds indoors if all else fails.
- Frost kills marigolds quickly, so protecting these flowers against frost is extremely important.
By diligently keeping track of the weather when there is still a possibility of frost, you can act to save your marigolds. Remember, a combination of warm soil and protective coverings is the best way to keep your marigolds from suffering frostbite.