Broccoli (Brassica oleracea var. Botrytis) is considered a cool-season crop. In the spring, broccoli is frequently planted before the average date of the first frost, especially in climates with hot summers. In the fall, broccoli produces best when temperatures cool. You may wonder if broccoli is frost tolerant.
Broccoli can tolerate periods of cold weather. Here is what you need to know to help your broccoli plants manage those temperatures.
Is Broccoli Frost Tolerant?
Yes, broccoli is frost tolerant. It is considered frost-hardy. Broccoli can survive temperatures down to 26 degrees F. If the plant is covered with snow, it can survive even colder temperatures. The snow acts as a blanket and protects the plant from the cold.
What Is A Frost?
A frost is weather that is between 31-33 degrees F. A freeze means the temperature falls at or below 32 degrees F. A hard freeze means the temperature will be cold enough for a long enough period of time to kill or injure seasonal plants.
The most widely used temperature for a hard freeze is 28 degrees F or below. All of these terms are used when the weather is cold for overnight or a few days. Once the temperature dips below freezing long-term, most broccoli plants won’t survive.
What Temperature Is Too Cold For Broccoli?
Broccoli can suffer leaf damage and winter burn at temperatures from 26 to 30 degrees F. Below 25 degrees F, broccoli will usually not survive unless it is under a blanket of snow and the cold doesn’t last long.
Do Broccoli Plants Need To Be Covered For Frost?
Mature broccoli plants can survive a frost uncovered. Broccoli seedlings may suffer some damage to the foliage if left uncovered.
How To Protect Broccoli From Frost?
When you know a frost is coming up, water the broccoli plant. The moist soil will help protect your broccoli. As the ice, which is an insulator, thaws, it produces warmth. This means the plant is not as cold for as long as dry plants.
Covering your broccoli plants will help keep them warm, too. There are two ways to cover your broccoli during a frost.
Use a frost cloth to protect your broccoli from a frost. The white kind can be left on during the day for a few days. The sun can filter through the cloth.
The dark frost cloth must be removed every day for several hours to allow the broccoli to get the sun it needs to photosynthesize. Neither type of frost cloth is designed for long-term use.
Do not lay a tarp over your broccoli plants. The broccoli will freeze everywhere the tarp touches.
A low tunnel is a covering held up by half hoops of PVC or other material.
Low tunnels (Iess than four feet tall) trap heat radiating from the soil. This creates a microclimate several degrees warmer in the low tunnel than the air temperature outside.
Picking Broccoli Cultivars
In the spring, pick early maturing broccoli cultivars if you live where the summer is hot.
In the fall, you can pick longer maturing varieties that grow foliage while it is hot and produce the head after the weather has cooled down.
What Types Of Broccoli Will Frost Tolerant Better?
There are some varieties of broccoli that are more cold tolerant than others. Here are several varieties to try. Days to harvest are from transplants. Add 25-30 days if growing from seed.
This heirloom variety was grown by Thomas Jefferson. It is noted for its cold tolerance and large, full heads. Waltham29 takes 60-90 days to reach maturity.
A hybrid, marathon grows large blue-green heads that are ready in 62-68 days. This is a very cold tolerant cultivar.
Very cold tolerant, the hybrid Eastern Magic makes large blue-green heads in 60 days. It also tolerates heat well.
This variety is slower to mature, taking 63-68 days to mature. However, it is very good for growing in the fall because it is very cold tolerant. This hybrid also tolerates heat well.
This Italian heirloom has purple heads. It is very cold hardy. Plant it in the fall and it will overwinter and be ready in the spring. It takes about 200 days to mature if grown in the fall or 120 days if grown in the spring.
In conclusion, broccoli is frost-hardy. In fact, it is hardy to 26 degrees F, although it will have some damage to its foliage when it gets that cold. There are some cultivars that are more cold tolerant than others. Pick them for places where your season includes cold temperatures.