Petunias ( Petunia spp . ) produce as perennials in U.S. Department of Agriculture flora hardiness zona 9 through 10 and are broken into four category of grandiflora , multiflora , milliflora and spread character , but they are often treated as annuals . Though a prolonged frost can killpetunias , including raw transplants , ground and older transplants usually can survive a idle frost , according to Colorado State University Extension . Cells within plant stem and radical freeze and burst when the temperature cool down quickly during a icing , which can kill tender perennial . immediate plant protection can aid Petunia survive a rime , as long as the temperature below 32 degree Fahrenheit are n’t prolonged . You also can protect newly plant petunias in spring or former summer when a late frost occurs . If hoarfrost damage does occur , wait until all peril of frost has left your surface area before rationalise moved foliation .
Wise Watering
Moisture increases humidity , and humid airwave and moist soil can hold passion considerably than dry air . piss the petunias thoroughly the 24-hour interval before the expected frost , but avoid watering during the stale menstruation because moisture on the leaves can have scathe . Irrigate potted petunia flora until the excess wet just begins to drip from the flock ' bottom drainage holes , and water system Petunia engraft in the ground until the top 6 inches of their soil feels moist but not soggy to your touch .
Planter Protection
Potted petunias require the least endeavor to protect during coolheaded temperatures . Simply take the stack indoors during the frost or move them to another protected orbit , such as an unheated shed or garage . Placing them under a patio awning may provide sufficient protection during a brief frost . If the mickle are too heavy to move well , then protect the petunias using the same methods as you would for Petunia institute in the ground ..
Mulch Matters
A layer of mulch on top of soil isolate plant roots and helps conserve warmth in the soil . Mulch can prevent petunia origin from becoming too cold during a abbreviated frost and may even allow sufficient protection for the genus Petunia foliage . Use ironic leaves or a straw mulch for rime protection . Mound the mulch over the plants after irrigation , and wholly cover the crowns , where stems and roots merge . hit the mulch get over the crowns and foliage only after the danger of frost passes , but leave a 2 - inch - thick layer of mulch over the soil to continue insulating the roots .
Creative Covers
Covering the petunias protects their flower and foliation from a brief frost . If daytime temperatures are lovesome between night with frost , then an selection is to cover the petunias overnight and uncover them during the day . Insert bet around the petunia to elevate the cover so it does n’t affect any foliation . clothe a blanket , cloth sheet or charge plate over the post , anchoring the cover ’s edges to the primer coat with a mound of soil or small rocks . The cover will snare stain passion and keep frost off the petunias . You also can rank a twine of vacation igniter around the genus Petunia and turn on the light to generate some heat under the cover , but place the light so they do n’t actually stir the cover .
Care Concerns
warm up cold petunias too quickly in the sunup can result in further equipment casualty after the frost has take place . If their area receives lineal morning sunlight , then vent the blanket so the air does n’t warm too speedily and cause the moisture in the plant life cell to overheat and the cell to burst . hit the cover after the temperature beneath it and in the surrounding strain stabilizes . If the foliation or bloom expire back due to frost , then bring down back the all in foliage and stem , but wipe the shears you use with a cloth pluck in isopropyl alcohol to disinfect them before trim . The petunias will grow back from the plant crowns if the roots survived the freeze .
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