Do Perennials Need to be Protected from Frost?

Do perennials need to be protected from frost?

As the winter approaches, many people wonder if they should protect their perennials from frost. It is a common misconception that perennials can handle any cold weather.

In reality, protecting your plants in colder climates will help them survive better and thrive for years to come!

The best way to protect your perennials is by covering them with a thick layer of mulch, which keeps the plant warm and helps control weeds and prevents soil erosion!

Should you Cover Perennials for Frost?

A perennial shrub that is winter hardy to your area will most likely not need to be protected. That is why I always advise new gardeners to try to grow, as much as possible, plants that are indigenous to your area. 

Most indigenous plants will snap back as soon as the weather warms.

Many perennials will adapt to your conditions because they are not in complete contrast to the plant's requirements. For example, I have some tender perennials planted against a warm wall that protects them from freezing.

Most newly planted young perennials will need winter protection as they will not be mature enough to handle frost.

How Cold is too Cold for Perennials?

A "hard frost" with temperatures below 28F (-2C) will kill frost tender plants from warmer climates and may kill off the top growth of hardy perennials.

Leave this dead matter on the plant to protect it against more frost damage and remove it once all frost has passed.

Frost-hardy plants can survive when the cold temperature dips below freezing, but they will not grow. Therefore, the best time to plant new perennials is in late summer or early fall, so their roots have a chance to establish before winter.

Frost Hardy Perennials

Some frost-hardy perennials are Peony, Lily of the Valley, Yarrow, Coneflower, Hosta, Coral Bells, Catmint, Artemisia, Aruncus, Delphinium, New England Aster, Blue Oat Grass, False Indigo, Ajuga, Day Lilies, Spiderwort, Shasta Daisy, Scabiosa, Sedum, Penstemon, Ornamental Grasses, Salvia, Columbine, Japanese Anemone, amongst many others.

Can Plants Recover from Frost?

Plant shock due to frost is easily detected. Their foliage will droop or curl from damaged cells. Leaves turn dark red to brown and may die and fall off.

If the frost damage is not too severe, plants may recover. However, new shoots in early spring or new growth from summer pruning won't show until warmer weather.

Tender plants and tropical plants will have to be treated as annuals and will not recover from a heavy frost or a light frost for a long period.

Protecting Tender Perennial Plants From Frost

The best protection from frost damage is to mulch the root zone with a barrier of organic material up to 4 inches (10cm) deep and cover plants with a frost cover.

Frost cover is a fabric covering the plant with an air space between it, and the ground so cold air can't reach roots. The cover should also be anchored in place to avoid the wind blowing it off.

To protect frost-sensitive plants, wrap them in heavy-duty frost protection fabric. Remove these covers when temperatures have risen above freezing for at least 12 hours, but wait until the soil is dry before removing them.

Here are some other tips to protect your pot plants from frost:

- Move tender perennials to a more protected area, like under the eaves of a porch or into sheltered corners where cold air cannot penetrate and water supplies won't freeze.

- Put potted plants on a table, porch or balcony where they will be warmer than on the ground.

- Cover pots with a light frost blanket to trap heat and keep them from cracking in freezing temperatures. 

- Choose frost-resistant plants that grow best in your climate zone, so you won't have as much stress come winter.

The most important thing is not to panic. If a hard frost is predicted, take the appropriate steps to protect your plants and wait for warmer weather and the growing season to resume routine plant care.

Protect Plants from Late Spring Freeze.

Sometimes gardeners are surprised by a cold snap with late spring freeze damage when flower buds are forming.

Keep an eye on the weather reports during spring. 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.