1. ZZ Plant. Alternatively known as the Arum Fern, the ZZ Plant is an iconic houseplant that is best known for its bright, green foliage. The defining quality of this plant, however, is the fact that it can withstand any degree of winter cold.
Leafy vegetables like cabbage, lettuce, kale, collards, and chard can tolerate some frost. Early spring blooming flowers like crocus, snowdrop, and primrose can all survive the winter, and pansies are especially resilient.
An important factor in the chance of survival is how long the plants were exposed to cold temperatures. A few hours can do the job, depending on the plant. Generally, though, it takes 12 to 24 hours of exposure to cold temperatures to completely kill most tropical plant species. If you're in doubt, check the roots.
To protect plants from frost, you will need to cover them to keep the moisture from freezing. While an unexpected frost can leave many gardeners scrambling to find anything to cover their tender plants; it is important to use the right materials.
Choose The Right Containers
Terra-cotta and ceramic pots absorb moisture, which expands as it freezes and cracks the container. Metal, concrete and wood containers typically handle freezes well, as do fiberglass and resin pots. Some plastic pots also survive winter fine, but may become brittle over time.
A hard freeze in May is not uncommon for some areas and can kill tender perennials. Hardy plants such as daylilies, hosta, peonies, lily-of-the-valley will survive a late spring frost, but they will be out of commission until warmer weather returns. These are perfect times to replace them with frost-resistant plants.
The snowdrop flower.
As a plant that actually despises warm winters, the snowdrop flower performs its best in frigid temperatures. This flower can withstand temperatures down to -30 F. while still displaying its bright green stems and delicate, white flowers.
Start by heavily mulching the roots of the plant with either wood mulch or hay. For added protection, you can nestle gallon jugs of warm water into the mulch each night. This will help drive off some of the cold that can kill the roots.
A mature, cold hardy plant can withstand actual freezing temperatures (32F/0C) for a period of time and even temperatures below freezing. Cold hardy plants can easily handle light to moderate frosts without being harmed. Another way of saying this is these plants can tolerate a hard frost.
While some plants are well adapted to the cold, a bad season can cause damage to even the hardier trees, shrubs, and perennials. Plants are vulnerable to a range of different damage throughout the winter season. Simply freezing, for those plants that are not cold tolerant, usually means death for the plant.
Daffodils, crocuses and tulips
Hardy all the way to zone 3, they actually do better with cold winters. These plants need cold weather to bloom well in the spring, thanks to a chemical reaction that takes place when the soil temperature is below 55 degrees, according to the Amsterdam Tulip Museum.
Most roses can withstand a quick cold snap of temperatures down to 10 degrees F, but it is best to protect them if you expect an extended period of time when temperatures dip under 20 degrees F. The amount of protection your roses need depends on the climate in which you live.
Thoroughly Water plants if it's not going to rain before the freezing temperatures arrive. It may sound illogical. However, a moist ground stays warmer than dry soil. Watering the night before the freeze comes will insulate the root structure of the grass and plants and decreases the potential for cold injury.
To know when to cover your plants, you need to know when the plants you have are susceptible to frost damage. Some frost-tender plants need to be covered as soon as the temperature hits 32°F, while others can handle lower temperatures and/or longer freezing periods.
Most houseplants are tropicals and prefer temperatures between 65-75°F during the day and about 10 degrees cooler at night. For many plants, temperatures below 50°F can cause problems. Adjust thermostats to cater to your comfort, but remember your plants need some consideration.
Suitable plants
Try box (Buxus sempervirens), bay (Laurus nobilis), skimmia, euonymus, ivy (Hedera) or Gaultheria mucronata varieties. Ornamental cabbage and kale provide additional foliage interest.
From that experience, I've found the best frost protection for your outdoor plants is either free or cheap. Cardboard boxes and brown grocery sacks make perfect frost cover and at the end of the season can be recycled. I keep various boxes on the patio and when frost is forecast simply put one over the plant.
When Should You Cover Plants? Cover your plants at night and remove them during the day when the temperatures rise above 32 degrees F, so that the soil can warm up again. Some outdoor plants won't survive the harsh conditions of winter, bring them inside and use these tips for caring for them through winter.
It is best to water in the afternoon or evening the day after a freeze so plants have had a chance to slowly raise their temperature. After a freeze, soft-stemmed, non-woody plants such as impatiens, cannas, elephant ears, agapanthus, amaryllis, begonias, philodendron and gingers may be pruned back to living tissue.