Spring freezes are common at our altitude, and protecting perennials is all about preserving tender new growth that has already emerged.
When a freeze is forecast, as is this Monday, Tuesday and Wednesday nights cover plants with frost cloth, old sheets, lightweight blankets, or buckets/boxes. Ensure the covering touches the ground to trap heat already in the soil.
What to cover
Cover any plant that has already emerged and begun growing. Examples are tulips, lilacs, clematis, bleeding heart, hostas, hydrangeas, young shrubs, newly planted perennials, plants in pots, and emerging cold hardy vegetables like sweet/snap peas, radishes, spinach, kale, carrots, and spring onions.
Iris and daffodils should weather the freeze, but keep in mind that temperatures below 30 degrees F for 5-8 hours can cause buds to turn mushy and die. You can cut stalks with colored buds and bring them indoors to bloom instead of risking them freezing.
Take heart - even if frost damage occurs, many established perennials will recover. Resist cutting back damaged growth right away, as it can actually protect the plant from further cold snaps.
- Avoid plastic directly on foliage, as it can trap moisture and cause damage.
- Secure coverings so they don’t blow away, and remove them in the morning once temperatures rise.
- For extra protection of very valuable perennials, consider multiple layers of protective coverings.
- Cover in the afternoon tomorrow to trap soil heat, keep the covering on through Friday (we're expected snow and cold temps), and then remove all coverings Saturday as the sun begins to warm the environment.
- For smaller plants, inverted heavy pots, buckets, or cloches work well as quick protection.
- Moist soil holds heat better than dry soil, so water deeply tomorrow morning before Thursday night's expected freeze (22 degrees F). Adding a layer of mulch such as compost or pine needles (3-6 inches) helps insulate roots and stabilize soil temperature.
- For extra-sensitive plants in containers, consider moving them into a garage overnight or grouping them close to the house in a very protected spot and cover.
What to cover
Cover any plant that has already emerged and begun growing. Examples are tulips, lilacs, clematis, bleeding heart, hostas, hydrangeas, young shrubs, newly planted perennials, plants in pots, and emerging cold hardy vegetables like sweet/snap peas, radishes, spinach, kale, carrots, and spring onions.
Iris and daffodils should weather the freeze, but keep in mind that temperatures below 30 degrees F for 5-8 hours can cause buds to turn mushy and die. You can cut stalks with colored buds and bring them indoors to bloom instead of risking them freezing.
Take heart - even if frost damage occurs, many established perennials will recover. Resist cutting back damaged growth right away, as it can actually protect the plant from further cold snaps.