Twenty-one degrees is darn cold even for the hardiest early rising plants. That’s what we got down to early last week, and it broke a record.
Most of the trees that had started flowering last week seemed to end up with no more than browned blossoms. The exception was the magnolias. The cold turned their pink and white flowers to brown. Other than that, we might see some twisted and burned leaves in a few weeks, but there shouldn’t be any long term damage.
I expect this won’t be the last round of cold we see before mid-June so we need to plan for it. Many of the nurseries have plants out for sale that are very enticing. For the most part they will be fine if hardened off properly before they go into the garden.
In many cases, the plants have come straight out of warm greenhouses, were loaded onto a truck and delivered to the stores with little chance to acclimate to the colder outdoor temperatures. So when you bring them home, give them a few days in a sheltered spot outdoors to get used to the temperatures before you plant them.
As we get further into the spring and more plants emerge, the frosts can cause more damage. Annuals like petunias and snapdragons can take a frost while begonias and marigolds can’t. Cool season vegetable starts like lettuce, cauliflower, broccoli, Swiss chard and cauliflower aren’t fazed by the cold.
Warm season vegetable starts like tomatoes, pepper, eggplant, cucumber, squash, basil and melons will die if they get a whiff of 32 degrees. The long standing rule here is to wait until around Memorial Day to plant the tender ones.
One exception to even this rule is basil. When temperatures gets less than 35 degrees, basil dies. Rather than buying plants now, wait until late June and plant it by seed. You will have a nice crop by mid-August.
Let’s face it, a lot of you get impatient and plant anyway. Then the weather forecast calls for 30 degrees. Now what do you do?
The simple answer is to pay attention to the forecast and be prepared to cover things. Almost anything can be used to temporarily cover tender plants – cardboard boxes, plastic pots and buckets, tarps, bed sheets, milk jugs and soda bottles. All these will need to be removed in the morning so the plants get light and don’t overheat.
A more permanent method is to erect a temporary greenhouse over the bed. Lengths of PVC plastic pipe can be bent into hoops over the plants and set over stakes. The hoops can then be covered with spun fabric floating row cover or plastic and left until the danger of frost has passed.
The fabric will let in light, water and sun and can be left in place. The plastic will have to be rolled up during the day to allow the heat to escape, and the plants will also need to be watered.