Experiencing the first frost with your fig tree can be a nerve-wracking experience. What most new fig growers don’t understand is that frost can play a beneficial role in the health of fig trees. Dormancy triggered by frost is a vital biological advantage for deciduous trees like the fig tree. However, every year I get many questions from concerned fig growers about the impact of frost on their trees, and some even mistake its effects for damage.
This article also aims to define what is a dormant fig tree. That way, winterizing fig trees can be accomplished safely. I’ll even provide tips for those in frost-free locations. Remember, frost has settled on your fig tree, but it doesn't necessarily mean it's dormant. The key lies in understanding the process and waiting for specific indicators before taking winter protection measures.
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Fig Tree Dormant Season
Typically, fig trees require temperatures in the low 20s (Fahrenheit) or at least 2-3 lighter frosts before they truly enter dormancy. Many locations experience their first frost in October or November while warmer and Southern climate growers may have to wait until December or January.
After a hard freeze, the leaves of a fig tree will become brown, dried up, and most of which will fall off the tree. The fruits as well. Depending on the severity of the freeze and the low temperature, some figs and leaves will remain on the branches. Remove them prior to winter storage or performing your winter protection method.
Fig trees stay dormant until temperatures warm back up in the late winter or springtime as warmer soil temperatures are the main signal for fig trees to wake up from their winter slumber. Consistent soil temperatures over 45-50°F start this process.
Q: Is My Fig Tree Dormant?
A: It’s all about sap flow. Like most deciduous trees, the sap of a fig tree rises from the roots to the tips of the branches in the spring and flows downward for winter storage in the tree’s roots in the fall. Therefore, if you prune a branch and see little to no sap flow, it's a sure sign that the sap has returned to the roots. That is the best sign of true dormancy.
Why Wait for Dormancy?
It's crucial to wait for your fig tree to be fully dormant before taking any winter protection measures. Other than insufficient winter protection for fig trees, this is the other major mistake I see new fig growers make. Here's why:
Wrapping: Wrapping a tree with leaves can trap moisture and promote mold and disease growth.
Pruning: Pruning a non-dormant tree removes valuable carbohydrates (sap) that are stored in the roots during winter for vigorous spring growth and production.
Storage: Potted figs that are not fully dormant can wake up prematurely in winter storage, leading to a leafed-out fig tree growing in darkness usually many months away from your last frost date.
Fig Tree Cold Tolerance: Understanding Fig Tree Dormancy Temperature
While fig trees are known for their delicious fruit and vibrant foliage, their tolerance for cold weather varies greatly depending on the variety, age, and environmental factors. Understanding these nuances is crucial for protecting your fig tree and ensuring its survival during winter.
The type of fig you grow significantly impacts its cold tolerance. Most commonly found fig varieties can withstand temperatures as low as 10°F (-12°C) without taking damage. However, some hardier varieties, like the Chicago Hardy, can survive temperatures down to 0°F (-18°C) or even -5°F (-21°C) with proper winter protection.
Age and Lignification:
Regardless of the variety, young fig trees are more vulnerable to cold damage due to their imbalance of hormones leading to vigorous and poorly lignified growth. Similarly, mature fig trees that are pruned hard or are killed back by cold temperatures also suffer from the same imbalance.
Lignification is when branches harden and become woody, increasing their resistance to cold temperatures. Ideally, fig trees need to cease growth 3 months before the first frost to achieve sufficient lignification. Once a fig tree loses its leaves from frost, lignification slows significantly and eventually stops.
In humid climates, abundant water availability can also lead to a fig tree’s continuous growth late into the growing season. This makes them more susceptible to damage during even mild winters. For example, a poorly lignified Hardy Chicago fig that should be able to withstand 0°F (-18°C) can take damage at even 20°F.
Potted Fig Trees:
Because their roots are not protected by the earth's warmth, potted fig trees are susceptible to cold. Temperatures below 15°F (-9°C) can damage their roots, so it's crucial to move them indoors or to a protected location when temperatures are predicted to dip lower.
What to Do in a Frost-Free Climate
If you live in a frost-free climate, you can still help your fig tree enter dormancy by:
Manually removing the leaves: This mimics the effect of frost and signals the tree to store its energy.
Reducing water: This slows growth and encourages the tree to conserve resources.
Keep in mind, that this is not a sufficient practice in cold zones where long-term winter storage or winter protection is necessary.
Leaf removal and reducing water simulates a dormancy period and will provide the biological advantages growers desire from deciduous trees. However, it’s more so a quasi-dormancy or “half dormancy.” Not the true and full dormancy that can be achieved with cold winter temperatures or 2-3 frosts.
Check out my friend's "The Fig Hunter" on how they prepare fig trees for dormancy and prune them in Northern California.
Fig Chill Hours
The 100 chill hour requirement that fig trees “need” is regurgitated all over the internet. Another fact about fig trees that is unfortunately incorrect. Fig trees do not require dormancy or chill hours. However, dormancy is an advantage worth capitalizing on.
Don't be fooled by the first frost. Wait for several frosts with temperatures in the low 20s before assuming your fig tree is fully dormant.
Before taking winter protection measures, watch for signs of dormancy, such as defoliated trees, little to no sap flow, and fallen fruits.
If you live in a frost-free climate, manually remove the leaves to help your fig tree enter dormancy. Chill hours or dormancy is not required.
By being patient and understanding dormancy, you can ensure your fig tree has a successful winter and a healthy spring.