Growing in your Greenhouse: Citrus

Not sure if anyone noticed or not, but we are in the midst of citrus season. With winter comes the need to keep your immune system up and running to ensure we don’t succumb to any of the seasonable sicknesses. What’s a better way to deal with this situation than the tried and true method of eating a lot of citrus fruits! Not only is this prime citrus season in the United States (orange season in Florida ranges from October to June) but citrus fruits are also good for you. Vitamin C is a necessary dietary component that can help boost your immune system’s response to different illnesses like the common cold. Some citrus fruits, like oranges, are full of potassium as well which can help both with muscle cramping as well as immune responses. Eating fruit can also help you keep up with your New Year’s resolution (assuming you, like most, vowed to eat better this year). But never mind all that. Citrus fruits are, for the most part, delicious. Lemons are a staple in my kitchen throughout the year, but much more so in the winter. From baking with lemon curd, to brightening up a white wine pan sauce, they are very versatile ingredients. Limes are a great way to brighten up any meal that utilizes the heat and flavor of chilies. Key limes in particular are great for pies (who said eating fruit had to be healthy?). For whatever your reason, citrus is in season, so let’s explore citrus varieties you can grow on your own in your greenhouse.

First things first, the basics for growing citrus fruits in your greenhouse. This venture will likely be one of the more expensive and energy intensive paths you can take in regards to growing in your greenhouse. This is mostly due to the fact that you will be attempting to grow during the winter when there is characteristically less sunlight and colder temperatures. This pre-existing condition results in extra heating and lighting needs for your greenhouse if you wish to be successful. Cold temperatures will result in freezing the growth process and prolong the time to maturity, essentially ruining your plans to harvest during the winter. Generally speaking, the minimum night temperature for your greenhouse should be kept at 65-70° F. This will ensure that you are not spending too much on trying to keep your plants at proper temperatures all the while not letting your plants freeze. Higher temperatures can be used, if you don’t mind the energy costs, but be sure to not cook your plants before they’re ripe. If and when you are blessed with a sunny day during the cold season (rare I know, but they do happen) you can try and save yourself on heating costs by utilizing the power of the sun. If this is your course of action, stay on top of things! Turn off your heaters in the morning when you notice the sun making its way into your greenhouse. Make sure you properly vent your greenhouse to cut down on excess moisture buildup. Come early afternoon, when the sun has reached its peak in the sky and the temperature begins to drop, make sure you close your vents and set your heaters to turn on once the ambient temperature in the greenhouse drops below optimal levels. If you follow these few simple rules, you’re off to a good start. This, however, is far from all that you need to know when you are attempting to grow your own citrus trees in a greenhouse during the winter.

Once you’ve prepared yourself to grow tropical variety fruit trees in your greenhouse during the winter you’re ready to choose what exactly it is you’re trying to grow. There are a wide variety of different citrus fruits that can all grow in similar greenhouse settings. However, you may have limited space in which to grow said fruit. Many hobby greenhouses are not large enough to permanently house a fully grown orange tree, let alone a lemon or lime. Luckily, many citrus fruits already come in dwarf varieties so you don’t need to be a bonsai expert to grow viable fruit trees on your own. Dwarf varieties are great options for hobby greenhouses as they are much smaller in stature, thus requiring less energy and nutrient input. Not only are they less work and take up less space, the size of the fruit is generally the same size as their natural sized counterparts. Dwarf varieties are also less prolific in terms of production, which trust me, is a good thing in the long run. Anyone who’s had a full sized fruit tree anywhere on their property can tell you how much of a pain overproduction can be. You may think you want never ending fruit, but when your greenhouse floor is full of unused oranges, don’t come crying to me about it (though I would like to see a picture).

Now that you’ve figured out what you want to plant, you should make sure you have the proper pot or space to plant your tree. Citrus trees tend to be very top heavy which can make pot shopping a bit more complicated. Getting yourself a heavy, deep pot can help make sure the trees will be balanced while growing and fruiting. Ensure that the pot is large enough to give the root system plenty of room to get itself established and not be overly cramped. However, it should be noted that the larger the pot you provide for your citrus, the larger it will grow. You want to make sure that the pot you get isn’t going to encourage your plant to outgrow its surroundings. You also don’t want to get a pot too small and not let the rhizome grow strong enough. Just to stress this again, citrus trees are top heavy, so make sure the pot you get is deep enough to keep your tree from toppling over (I’m not sure how well a lemon bush would work out).

Growing things inside is always a bit more complicated. Generally speaking, your plants are only exposed to the fertilizers, nutrients and water you give it. The soil you choose for your plants can have impacts down the line in your plants life. Keeping that in mind, make sure you are choosing a good quality soil that has the necessary nutrients and minerals that the plants you wish to grow require. Citrus plants especially require iron in their diets, so if you notice your plants leaves are turning yellow, add some iron chelate as needed. Nitrogen is also a very important chemical in citrus plant diets, so using a water soluble fertilizer that is nitrogen rich is an important step in ensuring your plants successfully reach the fruiting stage. Once you’ve got the dietary part of things figured out, make sure you keep your eyes open for diseases and pests. By using an all-purpose disinfectant you can keep your greenhouse clear of viruses, bacteria, mildew and algae. If you’re having an aphid problem and you want a natural solution, ladybugs are a great solution! Simply introduce a few ladybugs into your greenhouse environment and let them get to work. If you’re moving your citrus tree into your greenhouse from somewhere else, make sure you disinfect your plant prior to putting it in the greenhouse to avoid spreading harmful entities that your plant may have picked up. Ensure your plants are properly spaced out inside the greenhouse, keeping the air circulating and making sure not to overwater. These simple steps should keep your garden clear of any pests, viruses or molds that could impact your harvest.

Positioning and watering may be some of the more challenging aspects of growing citrus trees. They are highly susceptible to root rot, fungus and other forms of plant diseases. Spacing out plants can help keep airflow going between them and keep excess moisture from gathering. These plants should experience anywhere from 8-12 hours of sunlight, real or artificial, with higher temperatures (below 85°) generally yielding optimal results. Soil should be kept moist, but on the dry side of moist. A good tip is to invest in a humidifier which can help keep ambient temperatures around the plants warmer as well as providing a source of incremental water. However, if you are using a humidifier (or pot of boiling water), make sure you are venting your greenhouse so excess moisture doesn’t cause problems.

Some final tips that might help you in your journey are not exclusive to growing citrus plants. Installing a thermometer in your greenhouse can help you stay on top of temperature requirements for your plants. We offer a climate monitor which will not only tell you the temperature, indoors and out, but can monitor the precipitation and provide a forecast as well. Make sure you are pruning off any damaged branches or leaves during the winter when the plant is partially dormant. One should also be sure to keep plants away from the walls of your greenhouse to ensure your plants don’t come in accidental contact with cold temperatures. When potting your plants (this might be out of order but I’m hoping you finished reading prior to starting your project) put some loose stones or bricks at the bottom of the pot before putting in soil to ensure extra water has a place to drain away from the roots. While on the subject, make sure you decrease the amount of water you are giving your plants during the winter months. The lack of prolonged sunlight and lower temperatures allow for less water usage by your plants, so excessive watering will only set back your project.

Hopefully you were able to get some amount of information from this article (helpful or not). Growing your own food can not only be a fun and interactive venture, but it can also be beneficial for your health in more ways than one. These winter months can be long and gray, especially in the Pacific Northwest, but growing in your greenhouse can be a great way to bring back some color and light into your life. Enjoy the sunny days when they come and try not to fret as much about all the rain. After all, Washington wouldn’t be the evergreen state without it! Until next week, take care of yourselves.

-Brian Bill