A late spring frost can severely damage many plants and make the growing season a challenge. In addition, if a cold spell occurs in early fall, the plants may begin their dormant stage even though you would normally have a few more weeks of growing and blooming time left. Fortunately, there are some measures you can take to temporarily keep your plants growing when it gets cold.
Choose a planting site that stays warm longer than others. Avoid low-lying areas, where it tends to be cooler. Areas that are protected from cold winds, such as near a fence or wall, stay warmer than those subject to high winds.
Amend the soil so that it drains water well. Well-draining soil helps roots grow deeper so they're less likely to freeze. To amend your soil, turn over the top 12 to 18 inches and mix in several inches of compost, peat moss or other similar organic matter.
Avoid fertilizing your plants in the fall, or decrease the amount by one-third to one-half if fertilizing is necessary. You do not want to encourage too much new growth, which will be susceptible to injury from a freeze.
Spread mulch under the entire canopy of your plants. Several inches of mulch (e.g., bark, wood chips, leaves) will help maintain soil temperatures even during unusual cold spells.
Cover the plants when frost is expected. Simply placing a lawn chair or sheet over them may work for small plants and mildly cold nights. For colder nights and larger plants, you may need to cover four wooden posts with a blanket, sheet or burlap that covers the entire canopy of the plant and touches the ground on all sides. On freezing nights, add a 100-watt outdoor light, being sure it is not touching the plant of the cover. Take off covers in the mornings.
Lay potted plants on their sides and group them together. Cover them with a blanket, sheet, burlap or frost cover. Place them under a large tree for extra frost protection.