Should I Cover Mums In Frost?

When It Makes Sense

• Good fit: You live in a region where nighttime temperatures briefly dip below freezing (e.g., 28‑30°F) and the frost is expected to last only a single night. A light cover can shield the foliage without causing overheating.
• Good fit: Your mums are newly planted, still establishing their root system, and the soil is moist but not saturated. A breathable fabric cover can help retain warmth while allowing moisture to escape.

When You Should Avoid It

• Warning sign: A prolonged deep freeze (multiple nights below 25°F) is forecast. Covering may trap cold moisture and increase the risk of rot, making it safer to accept some die‑back.
• Warning sign: The soil is water‑logged or the plants are already stressed by disease. Adding a cover can create a humid micro‑environment that encourages fungal problems.

Pros and Cons

Pros

• Provides a thermal buffer that can reduce leaf damage and preserve bloom potential for the following season.
• Simple and inexpensive; materials such as frost cloth, old sheets, or burlap are readily available.

Cons

• Improper covering (e.g., plastic sheeting) can trap moisture, leading to mold, stem rot, or overheating on sunny days.
• Time‑consuming to set up and remove, especially if frost events are frequent.

Decision Checklist

• Is the forecasted low temperature only marginally below the freezing point, and is the frost expected to be brief?
• Are the mums healthy, well‑drained, and not already suffering from disease or water stress?
• Do you have breathable, appropriate covering material and a plan to remove it promptly after the frost?

Alternatives to Consider

If covering seems risky, you can opt for mulching around the base with straw or shredded leaves to insulate the root zone, or choose frost‑tolerant mums that are bred for colder climates. Relocating potted mums to a protected spot such as a garage or unheated greenhouse is another low‑risk option.

Final Recommendation

Generally, covering mums is worthwhile when a short, mild frost is predicted and the plants are healthy and well‑drained. In cases of prolonged deep freezes, existing moisture problems, or disease pressure, it’s safer to rely on mulching or accept minimal damage. Always monitor weather updates and remove the cover promptly to avoid excess humidity. For high‑stakes situations—such as commercial growers or rare heirloom varieties—consult a horticultural specialist.