Fig Tree Masterclass | Growing Fig Trees in a Greenhouse

Summary

Imagine the delight of biting into a succulent, sweet fig, perfectly ripened, and knowing that you grew it yourself, right at home, in a greenhouse. Whether you're a gardening novice or a seasoned pro, the idea of growing your own fig trees may seem like a daunting task. However, with the right guidance and a little persistence, you too can enjoy the fruits of your labor.

This article will take you on a fascinating journey, unraveling the benefits of growing fig trees in a greenhouse and providing a step-by-step guide on temperature and water management, container selection, pest control, and much more. So, let's embark on this green-thumb adventure, turning your greenhouse into a fig tree paradise.

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Benefits of Growing Fig Trees in a Greenhouse

The most apparent benefit of growing fig trees in a greenhouse is getting an early start to the season. Figs are fall fruits, typically ripening between August and the first frost. For growers in shorter-season climates that lack the 150 to 180 frost-free days needed to reliably ripen main crop figs, using a greenhouse will jumpstart the season.

A controlled greenhouse environment allows your fig trees to awaken from dormancy well before their last frost date, thereby accelerating their ripening dates.

Another significant benefit of using a greenhouse is the ability to shield fig trees from rain, which can critically impact fruit quality, especially in the fig’s final ripening stage. Excessive moisture can lead to spoilage, mold, and an increase in fruit flies that might lay larvae into the fruits.

The skin of the fig is susceptible to absorbing water in the final ripening phase. If the fig absorbs too much water, the soluble sugar (brix) levels drop, leading to a decrease in fruit quality, taste, and potential spoilage. By growing figs in a greenhouse, you can maintain a controlled, dry environment that ensures higher fruit quality.

Growing Figs in a Greenhouse

Heat Management

Heat management is a crucial factor in the successful growth of fig trees in a greenhouse. It’s also one of the few major observable differences when we’re not growing under plastic or glass. Therefore, most of this article will focus on the finer details of heat management. If you can fully understand the topic of temperature and how that relates to growing fig trees in a greenhouse, that will make you the best fig grower possible.

While warmer soil temperatures are essential for fig trees to wake up from dormancy and start growing-- too much heat can be detrimental to their growth. To ensure the optimal growth and fruiting of fig trees, it is necessary to maintain an ideal temperature range in the greenhouse.

Fig Tree Temperature Tolerance

• The optimal temperature for fig trees is a soil temperature of 78 degrees Fahrenheit. A combination of external factors all affect the soil temperature including, but not limited to the air temperatures. To determine the soil temperature, I suggest investing in a soil thermometer.

• I recommend keeping air temperatures in your greenhouse above 50 degrees Fahrenheit when possible. Cooler air temperatures can lead to a cold soil temperature, which will slow the metabolism of our fig trees and therefore their growth, root development, and nutrient & carbohydrate flow, and more.

• If the greenhouse temperature rises above 100-110 degrees Fahrenheit for prolonged periods, it can harm the growth and fruiting of fig trees usually leading to leaf scorch from an increased level of stress and lack of soil moisture.

• A consistent soil temperature of 90 to 100 degrees Fahrenheit can cause fig trees to enter a state of summer dormancy which halts their growth. In such cases, fig trees will not continue growing until the soil temperature drops to a suitable level.

You can read about leaf scorch here:

Energy Surplus, Deficit & the Breakeven Point

Excessive heat can be detrimental to fig trees in more ways than one. Not only can it cause the trees to stop growing by inducing summer dormancy, but it can also trigger early fruiting. When fig trees fruit too early in their development after waking from dormancy, they may not have enough growth to support their fruit set while continuing to produce new growth. This is because fruit production requires a lot of energy, and the trees need sufficient leaves to produce carbohydrates from photosynthesis.

Think of each fruit as an energy expense and each leaf as an energy income source. More expenses than income or a breakeven point between the two, will not yield positive results.

Each leaf should correspond to a new fruit assuming your fig tree’s specific sunlight requirements are met. If the tree stops growing in the spring, you’ll be missing out on additional growth and additional fruits. The spring is a critical time of development for fig trees. Your goal should be to aid your fig trees in achieving as much growth as possible before the summer heat warms the soil to a point of 90F or more and growth ceases during summer dormancy.

To help your fig tree back into a state of an energy surplus, it is important to remove some of the fruits, even if they are in their early stages. By doing so, the tree can redirect its energy towards growth, ensuring that it has enough leaves to support the remaining fruits and new leaves.

Quantifying & Improving Fig Ripening Dates

Think of the number of heat units required by fig trees to set their fruit buds and the number of heat units required to ripen their fruits as two different entities. Often the number of heat units to set the main crop fruit buds on the new growth of the season is minimal. This is why fruit set can be seen too early and lead to the breakeven point or an energy deficit that I mentioned above.

The number of heat units required to ripen the fruits is a different story. There is a much higher heat unit requirement to ripen a fig that’s already been set.

For example, growers in regions with mild climates such as the United Kingdom and the Pacific Northwest may experience an earlier spring than those in regions with harsher summers, such as my Philadelphia area climate. Growers in those locations typically see fruit set earlier than I do, but because of my more intense summer weather, my fig trees typically ripen earlier. This is partly why greenhouses can be so beneficial for fig trees, especially in a climate with mild summers.

Figs normally take 60-90 days after they’re set on the branches to ripen, but in mild climates, it may take 120-150 days to ripen them. This proves the point that consistent and additional heat units, specifically warmer and optimized soil temperatures go a long way toward earlier ripening figs. A greenhouse for fig trees can act as a double-edged sword. It can be too hot leading to summer dormancy or fruit set that’s too early, or it can provide the extra heat necessary in mild climates.

Regardless, you can now see why heat management is critical.

Fig Tree Water Management in a Greenhouse

Water management is an important aspect of growing fig trees in a greenhouse. Figs require adequate water to support their growth and fruit development. Water also helps to cool down the soil providing an additional way of optimizing the soil temperature. In the beginning stages of development, it is crucial to give the fig trees enough water to support their growth and to set as many fruits as possible before the summer heat arrives.

As the temperature in the greenhouse rises, the trees will require more water to compensate for the increased evaporation and transpiration rates. The warmer the soil temperature, the more water the trees will need. Water is essential for the growth of fig trees and it is what I consider to be the on/off switch for growth. If the water supply is limited, the trees will stop growing.

Although it is quite rare, fig trees can be overwatered in a greenhouse environment, which can lead to root rot and other diseases. It is important to maintain a balance and avoid watering too much or too little. The soil should be consistently moist to saturated.

One effective method is drip irrigation, which allows for consistent and precise watering. I recommend using the blue Primerus 12.6-gallon-per-hour spot spitter emitters. These shoot water in a 360-degree direction rather than a cone allowing the surface of the soil to evenly moisten. For every fig tree, I recommend 2 periods of watering during hot and sunny days. For every 5 gallons of soil, each period of watering should last about 2 minutes. That’s roughly a gallon of water per day. The watering schedule should be adjusted based on the size of the container and the tree, as well as the temperature and humidity in the greenhouse.

Fertilizing Fig Trees

Fertilizing fig trees in a greenhouse is an essential aspect of ensuring their growth and development. The best fertilizer for fig trees should have a good balance of macronutrients and micronutrients. The three macronutrients, nitrogen (N), phosphorus (P), and potassium (K), play a critical role in plant growth and development. Nitrogen is necessary for leaf growth and photosynthesis, phosphorus is important for root development and fruit production, and potassium helps regulate water uptake and overall plant health.

A well-balanced fertilizer for fig trees should contain micronutrients, including calcium, magnesium, sulfur, zinc, copper, iron, and many other trace minerals. While these nutrients are needed in smaller quantities than NPK, they are still essential for plant health and should be included to some degree in the average well-balanced fertilizer found at big box stores or major online retailers.

I recommend adding higher quantities of magnesium, calcium, and sulfur. These can be added separately in the form of lime, gypsum, and other soil additives. Silica and trace minerals can be supplied to fig trees through diatomaceous earth and mineral-rich amendments like rock dust or greensand.

For fig trees planted in the ground, I highly recommend doing a soil test to figure out the necessary nutrient application. However, container fig trees need more fertilizer than trees planted in the ground because of their limited root system and less ability to access nutrients from the surrounding soil. In a greenhouse, keep an eye on nutrient leaching in containers. That could be an additional reason to apply more fertilizer.

To read more about fertilizing fig trees, check out the detailed article, here:

The Increased Importance of Sunlight in Greenhouses

If you follow along with my YouTube channel, you know that this year I have access to a whole new greenhouse space. In the past, I’ve been using a 6x8 ft Harbor Freight greenhouse. In just a short amount of time, I noticed a massive difference during this growing season vs. the prior seasons. Namely due to the differences in sunlight each greenhouse receives. The commercial greenhouse receives sunlight from sun up to sundown, while the location where I normally grow my fig trees receives only 5 hours of direct sunlight per day.

The difference in sunlight exposure between greenhouses caused the fig trees to branch out in more locations because more buds were activated due to the increased sunlight exposure. Where sunlight hits a bare branch, the fig tree naturally responds and knows to grow in that location. That’s pretty awesome, right?

This increase in additional branching led to an increase in the number of fruiting branches, which ultimately led to more fruit production.

This observation underscores the importance of optimizing sunlight exposure when growing fig trees in a greenhouse. Maximizing sunlight exposure through techniques such as staking and limb bending can help ensure that the sunlight each tree receives is maximized, leading to increased bud activation and ultimately more fruit production.

Proper pruning can also have a similar effect on sunlight and photosynthesis maximization leading to earlier, more, and better-tasting figs. Check out the full article on pruning, here.

It's also important to note that the intensity and duration of sunlight exposure can impact fruit production. Fig trees require a specific amount of sunlight to set fruit buds, and maximizing sunlight exposure can increase the number of fruit buds and improve fruit quality. In greenhouses, the sunlight is diffused because of the glass or plastic above. Therefore, an even higher focus on sunlight maximization inside greenhouses must be at the forefront.

To read more about the importance of sunlight in regard to fig trees, check out this detailed article, here:

Potted Fig Tree Care | Choosing the Right Container

When it comes to growing fig trees in a greenhouse, choosing the right container is essential as using the right type of container can help maintain the proper soil temperature and prevent the tree from drying out too quickly.

The recommended container for fig trees in a greenhouse is a white plastic pot. This type of container is preferred because it reflects sunlight and helps to keep the soil temperature around 78 degrees Fahrenheit, which is ideal for fig tree growth. Using a plastic pot also prevents the tree from drying out too quickly, as fabric pots tend to do, especially as the tree matures.

It's important to note that black pots, which are commonly used in colder climates like mine in Philadelphia and places further north, are not recommended for fig tree growing in hotter climates like Southern California, Arizona, Texas, and Florida. Black plastic pots can heat up quickly and make it harder to keep the soil temperature cooler in these types of climates even when not growing in a greenhouse.

Fig Tree Diseases | Concerns with Humidity

Humidity is another important factor to consider when growing fig trees in a greenhouse. While it's important to maintain a certain level of humidity for fig trees to thrive, too much humidity can be detrimental to their health. Excessive humidity can create an environment for mold and mildew to grow, which can lead to diseases like fig rust or anthracnose. These diseases can cause leaf drop, reduce fruit production, and even kill the tree if left unchecked.

Additionally, high humidity levels can negatively affect fruit quality. Figs are vulnerable to absorbing water during the final ripening phase, which can negatively impact their quality and taste. If figs absorb excess water from high levels of humidity or don’t shrivel on the tree due to lower levels of humidity, the levels of soluble sugar in them can drop, leading to decreased fruit quality and potential spoilage.

One of the significant benefits of using a greenhouse for fig cultivation is that it helps shield the fruit from rain and maintains a dry and controlled environment, ensuring higher-quality fruit. If your greenhouse is experiencing higher humidity (50% or higher), take steps to lower it for the sake of fruit quality.

To learn more about Fig Rust, check out the detailed article here to help prevent it!

Fig Tree Pest Management

When growing fig trees in a greenhouse, pest management is an important aspect to consider. Some of the most common pests that can infest fig trees in a greenhouse include scale, spider mites, aphids, and fungus gnats. Scale is a particularly difficult pest to deal with as they have a hard, waxy coating that protects them from most insecticides. The best way to deal with scale is to physically remove them with a soft brush or cloth and to spray the affected areas with a mixture of horticultural oil and insecticidal soap.

For spider mites, which are tiny, spider-like pests that can cause yellowing leaves and leaf drop, it's important to maintain a higher humidity level to discourage their growth. If an infestation does occur, spraying the affected areas with insecticidal soap can be effective.

Aphids are another common pest that can infest fig trees in a greenhouse. They are small, pear-shaped insects that can cause distorted leaves and stunted growth. One effective solution for aphids is to release ladybugs into the greenhouse. Ladybugs are natural predators of aphids and can quickly control their population. Another option is to spray the affected areas with a mixture of neem oil and insecticidal soap.

Finally, fungus gnats are small, dark flies that can be a common problem in greenhouses. They can cause damage to fig tree roots. One effective solution for fungus gnats is to use yellow sticky traps to capture the adults or an apple cider, soap, and water solution. It's also important to avoid overwatering the fig trees as this can create a moist environment that is ideal for fungus gnat larvae. Another solution is to apply a soil drench of beneficial nematodes, which are microscopic worms that prey on fungus gnat larvae.

You’re Now Ready to Grow Fig Trees in a Greenhouse

Hopefully, you’re now more convinced about growing fig trees in a greenhouse. With the right knowledge and attention to detail, it's an endeavor that promises rich rewards. The benefits far outweigh the challenges, from earlier fruiting seasons to more consistent and superior fruit quality.

With patience, care, and the practical knowledge shared in this article, you'll be well on your way to enjoying the sweet success of homegrown figs. So, don your gloves, gather your tools, and let's embark on this exciting journey of greenhouse fig cultivation together! Let me know how your greenhouse adventure is going down in the comment section below.