When Jack Frost Won’t Quit

There is nothing more frustrating than spending a spring day admiring your newly emerged bulbs and perennials, only to discover that the night will bring rapidly falling temperatures. All those tender tips are going to be lost to old Jack Frost and everything will be set back by weeks. Well, probably not. Those plants have survived the winter and are remarkable resistant to low temperatures.

Our worries should be directed at fruit trees that are blossoming. Cold temperatures and frosts during the period that fruit trees are flowering will almost inevitably ruin the blossoms that are opened. Depending on when the frost hits, anything from some to the entire crop will be lost. You can check if the blossoms have been affected by opening the swelling below the blossom. If it is brown inside it has been touched by the frost and will not produce fruit. There is little that the home grower can do to protect backyard fruit trees.

Merging bubs are probably safe from late frosts. The growing leaves are unlikely to be harmed; the flowers are another story. Even crocuses will not survive heavy frosts or light snow. You can try covering bulbs that are already in bloom, but it has been my experience that it does more harm than good. Unless you take the time to build a tent over the flowers they are usually broken or flattened by your efforts to save them.

Perennial are fairly tough and only temperatures below 30 degrees F are going to cause injury.  Lilies however are susceptible to frost.  You want to take particular care with them because damage to the growth tip can prevent flowering and even further growth. Mounding some dirt or mulch up around perennials will usually take care of the problem.

If you have tender annuals already in the ground when that late spring frost hits covering them is an option. Sheets of plastic may be used if you allow a layer of air between the plastic and the plant. It they are in contact the plant will “burn” right through the plastic. You can cover your plants with buckets or even tent newspapers over them. A bucket also works over a perennial that is too tall for mulching.

Covering should probably be removed the next day but some of them can be left on without damage if another cold night is coming. Buckets will not cause a problem and neither will newspaper tents. Plastic however should be removed especially if the day is going to be sunny.

If nights are persistently cold, and your plants are small enough, you can cover them with clear milk jugs. Cut out the bottoms and remove the lids. These will provide nighttime protection against frosts and cold temperatures and need not be removed doing the day. Usually the hole at the top will provide sufficient ventilation. This method will give heat loving plants a jump start in the spring.

What you are doing in all of these methods is trapping daytime heat and heat from the ground around the plant. These few degrees are frequently enough to keep plant cells from freezing. A blanket of clouds serve the same purpose on a larger scale and this is why we see frost damage on clear nights. When old Jack Frost shows up just outwit him.