Yes, you should cover highly sensitive plants at 38°F. While frost technically occurs at or below 32°F, microclimates in your yard mean the air near the ground can be significantly colder than the official forecast.
The general rule of thumb is that most plants freeze when temperatures remain at 28°F for five hours. Of course, there are exceptions to this rule. Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F. Tropical plants have differing low-temperature thresholds.
Whether 40°F is too cold depends entirely on the type of plant. While hardy outdoor plants can tolerate freezing, 40°F is the danger zone for most indoor, tropical, and warm-season crops.
Starting in mid to late September, it is beneficial to watch the forecast and take note of forecasted low overnight temperatures. Once temperatures dip to the mid-30s °F, it will be necessary to take action by bringing plants indoors, covering plants, or utilizing cold frames and hoop tunnels.
Most houseplants are native to tropical areas and will not tolerate freezing temperatures. Many indoor plants will see damage when temperatures drop to the mid-to-lower 40s°F, and nearly all will die if exposed to temperatures below freezing.
At 38°F, hardy plants will be fine, but tropical plants, succulents, and seedlings will likely suffer cold damage or die. While it is above freezing, this temperature is dangerously cold for sensitive species.
Plants prefer to rest between waterings. Keeping the soil too moist all the time can rot the roots. OVERWATERING is the #1 killer of houseplants.
For most plants, any nighttime temperature below 40∘F40 raised to the composed with power F40∘F (4.4∘C4.4 raised to the composed with power C4.4∘C) is dangerously cold, with actual freezing (32∘F32 raised to the composed with power F32∘F or 0∘C0 raised to the composed with power C0∘C) causing severe cellular damage or death. However, the exact threshold depends heavily on the specific plant type.
Plants will not freeze at 39°F, as freezing begins at 32°F. However, 39°F can still cause severe cold stress or damage to sensitive, warm-weather plants.
Cover your plants before sunset whenever the overnight temperature is forecasted to drop to 32∘F32 raised to the composed with power cap F32∘𝐹 (0∘C0 raised to the composed with power cap C0∘𝐶) or lower. Covering them in the late afternoon traps the residual heat from the sun and soil, protecting your plants from frost and freeze damage overnight.
Bring your plants indoors when nighttime temperatures consistently drop to 50∘F50 raised to the composed with power F𝟓𝟎∘𝐅 to 55∘F55 raised to the composed with power F𝟓𝟓∘𝐅. Do not wait until the first frost, as exposing tropical plants to temperatures below 45∘F45 raised to the composed with power F45∘F can cause irreversible cold damage, leaf drop, and root shock.
The classic plant that universally says "I love you" is the Red Rose. However, if you are looking for long-lasting houseplants or specific symbolic meanings in the Victorian language of flowers, there are several wonderful alternatives to express your deepest affections.
The "3-hour gardening rule" is a safety guideline advising gardeners to avoid working outdoors between 11 a.m. and 2 p.m. during the summer months. This window is when the sun’s UV rays are at their strongest and temperatures peak, posing risks for both you and your plants.
At 35°F (1.7°C), you generally do not need to cover established or hardy plants, as frost forms below 32°F (0°C). However, you should cover tender annuals, tropicals, or young seedlings, because temperatures below 40°F can stunt or damage vulnerable growth.
Yes, you can leave plants covered for 2 days, but the safety of this depends on the material you use and the daytime weather.
Fall-seeded Cover Crops.
Small grain options include cereal rye, barley, oats, wheat, spelt, and triticale. Cereal (aka winter) rye is the most cold-tolerant and puts on growth even late into the fall when days are mild. It develops a root system that holds soil in place over the winter and in early spring.
Whether plants are okay at 40°F depends heavily on the specific type.
Yes, many plants can survive a single night of freezing temperatures, but survival depends entirely on the type of plant, the severity of the freeze, and whether it was protected.
In gardening, the "3-year rule" is a common guideline describing the three-stage establishment cycle of new perennial plants, shrubs, and trees. It states: "The first year they sleep, the second year they creep, and the third year they leap."
At 36°F, it is not too cold for hardy perennials and cool-season vegetables, but it is dangerously cold for tropicals, houseplants, and warm-season annuals. This temperature sits right at a "frost advisory" threshold, where moisture in the air can create ice crystals that damage sensitive plant cells.
To keep plants warm on a cold night, drape frost cloth or old blankets over them, reaching all the way to the ground to trap soil heat. Anchor the edges securely against the wind. For added warmth, place water-filled jugs that absorbed sunlight during the day near your plants.
Plants that are too cold will show signs of cellular damage or halted growth. Watch for wilting or drooping leaves despite moist soil, soft and mushy stems, or the rapid development of black, dead patches. You might also notice premature yellowing, dropping leaves, or a completely loose root ball.
Certain indoor plants are notorious for their demanding environments and hyper-specific care routines. The absolute hardest houseplants to keep alive include the Maidenhair Fern, which quickly turns to dust if its delicate soil dries out even slightly, and the Calathea (or Peacock Plant), which requires distilled water and 60%+ humidity.
It is not recommended to spray Dawn dish soap on plants. Dawn is a heavy-duty detergent designed to strip grease. When applied to foliage, it strips away the plant's natural, protective waxy layer, which can cause leaf burn, dehydration, and leave the plant vulnerable to pests and diseases.
Several plants in nature contain potent toxins that can lead to muscle weakness or paralysis if ingested or, in some cases, touched. Identifying these plants is crucial for safety and preventing accidental poisoning: