You know those tiny oranges you buy in big bags at the store? The ones you can peel in one long strip that taste super sweet? They’re called clementines and they’re not exclusive to stores. You can grow them at home by having your own clementine tree!
It sounds too good to be true, but clementine trees are great houseplants that are fairly easy to care for. In fact, if you haven’t grown citrus trees before, this is a great starter. Clementine trees are more durable and forgiving than their relatives. Plus, they grow just about the sweetest mandarins out there!
In this article, we’ll answer all your questions such as ‘What is a clementine?’ and ‘How am I supposed to grow a tropical fruit in the United States?’. By the end, you’ll be all set to get planting, cultivating, and munching.
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- Espoma Organic Soil Acidifier
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- Kensizer Yellow Sticky Traps
Quick Care Guide
| Common Name(s) | Clementine, Christmas Orange, Sweet Tangerine |
| Scientific Name | Citrus reticulata ‘Clementine’ |
| Month(s) of Harvest | 4 months |
| Light | Full sun |
| Water: | 1x weekly, more for young trees |
| Soil | Sandy, mildly acidic, and fertile |
| Fertilizer | Every other month |
| Pests | Fruit flies, leaf miners, soft scale |
| Diseases | Phytophthora, canker |
About The Clementine Tree
Clementines are cultivated hybrids that don’t grow on their own in nature. They’re believed to have originated in Southeast Asia, where they’re still widely produced. These trees are well-suited for the tropics, subtropics, and the Mediterranean.
In the United States, you can grow these mandarins outdoors in growing zones 9-11. If you aren’t lucky enough to live in such a warm growing zone, you can keep the tree inside and set it out during the summer. Clementines are often grafted, so it’s easy to find one with the rootstock of a dwarf tree. These will grow up to 6 feet tall instead of 25.
The tree itself is quite ornamental. It has a rounded, evergreen canopy of bright green leaves. In the spring, it features fragrant white blossoms that transform into 3” baby mandarins. The fruits ripen from November to February, earning them the name Christmas orange. They have a thin, loose peel and are typically seedless. This plant usually has thorns, but that’s not much of a deal-breaker if you add in the fact that it’s also known for a high pest-resistance.
Clementine Vs. Mandarin: What’s The Difference?
They may look similar, but clementines and mandarins aren’t the same thing. Taxonomically speaking, mandarins are a species of citrus fruit (Citrus reticulata) and clementines are a hybrid variety of that species (Citrus reticulata var. Clementine). The origin of this variety has been long debated and the current theory is that it’s a cross between a mandarin and sweet orange. So, all clementines are a type of mandarin, but not all mandarin oranges are clementines.
There are tons of other mandarin varieties – tangerines, Murcotts, and satsumas to name a few. Out of them all though, clementines are the smallest and, in our opinion, one of the sweetest. They stand apart with their dark yellow-orange peels and squat oval shape.
Planting Clementines
Whether by seed or start, plant your clementine tree in the spring or fall. If your growing zone allows it to stay outdoors, choose a location with plenty of sun and space. Keep the thorns in mind since you probably don’t want them snagging you each time you walk through the garden. Give yourself plenty of space for easy maneuvering.
Check the soil drainage and fertility, adding sand and organic matter as needed. It needs to drain well and be chock-full of nutrients for the new plant. If you’re planning to grow this tree in a container, choose one that’s light enough to move around or has wheels. Air pots on some kind of wheeled foundation will work excellently.
Planting citrus tree starts is pretty simple. Remove the start from its container and dig a hole slightly larger than the rootball. Gently loosen the roots to help them take to the new soil. Now, just stick it in the ground, fill in the soil, and give it some water. You may want to add a thin layer of mulch on top to preserve moisture, especially if it’s in the ground.
Seeds should be thoroughly cleaned before planting to avoid mold growth. Soak them in warm water overnight to remove any remaining pulp (this will also encourage germination later). If you aren’t going to plant right away, dry the seeds completely and store them in an airtight container in a cold place. Otherwise, plant them ¼” deep in moist potting soil, place the container in the sun, and keep the soil moist. To lock in humidity, cover it with a punctured, clear covering until the seedling pops up to say hi.
Clementine seeds germinate in 2-4 weeks but take 2-3 years to grow into mature trees. Don’t transplant your seedling until it has some strong roots and is actively growing. Over time, you’ll need to repot it every 2-3 years, changing out the soil completely, to keep it well-fed.
Care
The care requirements for clementine oranges are about the same as other citrus trees. If you can master this tree, just think how many other citrus fruit you could grow!
Sun and Temperature
In order to grow the best citrus fruit, these trees need full sun. Give it the brightest location you have, especially if it’s indoors. If you just don’t have an indoor location that’s sunny enough, you may need to supplement it with a grow light. In a pinch, clementine fruit trees will tolerate partial shade, but they usually won’t produce as well.
This plant can handle cold temperatures as low as 20°F, but we don’t recommend you test that. Exposure to frost can hinder fruiting or potentially be fatal. Keep your clementines fruit nice and warm with temperatures above 50°F. In extreme heatwaves though, you’ll want to give it some protection so it doesn’t get sunburned.
Watering & Humidity
The soil needs to be consistently moist but definitely not waterlogged. To achieve this balance, water when the top inch or two dries out. Depending on location, you’ll likely be watering it weekly. If it’s a very young tree, it may need to be watered as much as every 2-3 days during its first year of growth.
To prevent overwatering, keep an eye on the soil drainage and don’t forget to empty the water tray for container-grown trees.
These are tropical trees, so they can tolerate high humidity. If you’re growing it indoors, keep the citrus tree away from heaters that can dry it out. Use a humidifier or place the container on a tray filled with rocks and a little water to create evaporative humidity around the plant.
Soil
Outdoors, you’ll need sandy, slightly acidic soil. This plant is flexible with other soils, but for it to really thrive these requirements are important. Determine if your soil drains well by watering it and watching it drain. It should drain fairly evenly and quickly without any puddling. If there’s room for improvement, mix in some sand or perlite.
The best way to determine the pH is to use a home-testing kit. As mentioned, you’ll have to amend the soil so it’s slightly acidic or at least balanced. Use a commercial soil acidifier containing sulfur and gypsum to gradually bring the soil to a slightly-acidic level. Citrus can grow in neutral soils as well, but the fruit will often be sweeter if the soil’s lightly acidic!
Add a few inches of light mulch in the summer. This will lock in moisture so you won’t have to water as often. It’ll also keep the soil supplied with organic matter, which will be high in demand with this tree. Don’t place the mulch right against the trunk, however; leave at least a few inches between the mulch and the tree trunk.
For indoor plants, you’ll have the best luck with specialty citrus soils. You can find them almost anywhere and they already contain everything these fruit trees need. It still needs to be well-draining, but loamy soil is preferred for these container plants.
Fertilizing
Feed your clementine mandarin every other month throughout the year (these trees don’t go dormant). If you’d rather use a slow-release fertilizer, apply it at least at the beginning of spring and fall. We highly recommend using a citrus fertilizer as they’re tailored to this tree’s needs.
Pruning
Even if you’re growing a dwarf tree, pruning shouldn’t be overlooked. Like a good haircut, trees require regular trims to keep them healthy and in shape. You can prune your clementine mandarin any time of year, but during spring is preferable.
Clean your shears first and then evaluate the tree. Look for and trim back the following things:
- Branches obstructing walkways
- Dead or dying branches
- Crossing branches in the center of the canopy
- Offshoots (also known as suckers)
- Leggy branches
As a general rule of thumb, only prune up to a third of the plant at a time. Also, be conscious of which branches are flowering or fruiting so you don’t remove them all.
Propagation
You might be wondering, how do you grow a clementine plant from seed if the fruit is seedless? Farmers around the world achieve this thanks to a botanical phenomenon – parthenocarpy. Some plants, including clementines, can produce without being fertilized. Because the reproduction process hasn’t been started by pollination, seeds rarely develop in the fruit.
This mandarin variety requires cross-fertilization, so if the tree is isolated or only surrounded by clones of itself, it can’t be pollinated. This leaves it to produce parthenocarpically. Likewise, if you keep your plant isolated during blooming, it’ll produce seedless fruit.
If you do come across a clementine with seeds, that means some brave little bee managed to cross-pollinate it. The plant that grows from that seed may vary from the original tree because it contains DNA from a different tree. To keep the clementine variety from being lost after multiple cross-pollinations, these trees are propagated asexually by grafting.
The most popular grafting method for young citrus trees is budding. This is when a bud is taken from the scion – in this case, a clementine tree – and grafted onto the rootstock. A wide variety of rootstocks are compatible with this plant, but they have to be citrus. To choose one, consider where you live and what properties the rootstock will need (pest resistance, soil demands, etc.). If you aren’t sure, the best thing to do is to ask a local nursery or agriculture department what they suggest for your area.
The budding process is simpler than grafting the whole scion. There are several different methods, so we’ll just cover T-budding, also known as shield budding. Here’s what you’ll need:
- A healthy, mature clementine tree
- A healthy, actively growing rootstock of your choice
- A sharp, clean knife
- Grafting tape
Begin by selecting the clementine bud you’ll graft. Choose one that’s large, healthy, and preferably right next to a leaf. Clip off the leaf leaving the petiole so you have a little handle to hold onto. With your knife, cut the bud off the branch using an upwards slicing motion. Leave about half an inch below and above the bud and make it deep enough to include bark and a sliver of wood.
Now we move to the rootstock. It must be actively growing for this to work. Check this by peeling off a piece of bark. If it comes off easily, the tree is growing. If not, you’ll have to wait. Choose a healthy, mature spot on the trunk and make a vertical cut that’s slightly larger than the bud cutting. It should be deep enough to cut through the bark but not the wood underneath. Turn that vertical cut into a T by cutting a horizontal line on top that’s slightly wider than the bud. Carefully peel back the corners of the bark, revealing a pocket underneath (don’t tear the bark).
Grab your bud cutting and gently slide it into the pocket. Close the bark around it so just the bud and petiole are sticking out. Use grafting tape or something similar to wrap the graft. Now you leave the bud alone to heal. When it’s securely connected to the trunk, remove the tape (unless it was biodegradable). Chop off the rootstock right above the bud so the tree will direct its energy into the bud’s growth.
Harvesting and Storing Clementines
You’ve planted your tree, fertilized it, and cared for it like a child. Now, the tree’s ready to give something back!
Harvesting
Your clementine trees will be ready for harvest from early to mid-winter. The mandarins don’t ripen after being picked, so you’ll have to get them on time. When ripe, the skin turns completely orange with no green left. It will be a little heavy and give slightly when pressed. Pick it by hand or with clippers.
These mandarins don’t overripen easily and last on the tree for months. However, we recommend you pick them before winter’s over to prevent rot.
Storing
A fresh clementine orange will last about one week in the pantry. Keep it in an open container in a dry cool spot for best results. For a longer life though, refrigerate your mandarins in an open plastic bag, mesh bag, or just in the crisper drawer. As it ages, the mandarins will shrivel and lose their flavor. Remove any overripe mandarins before they spoil the others.
Mandarins can also be dehydrated for use as tasty, healthy snacks. Place each wedge on a dehydrator tray and dry them at 125°F for 10-12 hours. Store the dried treats in a vacuum-sealed bag.
To properly store clementines in the freezer, separate your fruit into wedges and lay the wedges on a metal sheet pan. Once the wedges are completely frozen, you can remove them from the pan and place them in a zip-top freezer storage bag. To thaw them back out, place your mandarins in a bowl or container in the refrigerator to gradually thaw.
It’s very common to store mandarins as juice or preserves. Juice should be frozen. Preserves can be canned as jams or jellies, but be sure to use tested and food-safe canning recipes.
Troubleshooting
Lucky for us gardeners, clementine trees don’t have any serious problems. However, you still need to be vigilant at watching for symptoms.
Growing Problems
Yellowing leaves are a common yet solvable problem. The usual culprit is a lack of sunlight, which is remedied by moving the tree’s location. If the leaves are only yellowing in the center of the canopy, you’ll need to thin it out so the sun can reach each leaf.
If your trees are exposed to cold temperatures, even infrequently, they may not fruit. Prevent this by moving them indoors on time. If you don’t think the temperature is the problem, check that your fruit trees have enough sunlight.
For indoor trees, under or overwatering can lead to leaf drop. Check that the soil is draining well and water more carefully. It can be helpful to make a watering schedule to help keep you on track.
Pests
Fruit flies are the pests you’re most likely to encounter. Besides lazing around the kitchen, these annoying bugs lay their eggs on fruit – on or off the tree. The best way to prevent them is by keeping the tree clean, removing dead material or fallen fruits, and harvesting on time. Horticultural oil may keep some species at bay. Placing a yellow sticky trap in the tree can help you easily see if you’re having an outbreak.
A pretty interesting insect, the citrus leaf miner literally mines tunnels through young leaves. The winding pathways are visible from the outside of the leaf and will eventually cause it to curl. This is very damaging to young trees but doesn’t affect the yield of mature ones. However, the damage may invite bacteria and infections. If only a few leaves are affected, remove them from the tree and burn them. Large populations can be prevented by periodically spraying new growth with neem oil.
Soft scale feeds on plant sap and can cause considerable damage over time. They leave behind honeydew, which is a sticky substance that invites sooty mold and ants. These pests also cause wilting and leaf drop. To get rid of them, apply horticultural oil, neem oil, or insecticidal soap to the trees. Like most pests, populations will be much easier to control if caught early on.
Diseases
Citrus gummosis, also known as Phytophthora, is a disease that attacks the bark. It causes sap to ooze from the trees, bark to fall off and leaves to lose their color. You’ll also see nasty-looking lesions on the tree. This disease is encouraged by damp, cool environments. Prevent it by only using well-draining soil and not overwatering. To treat it, remove infected bark and add copper fungicide to the rest.
If you see clusters of brown, raised lesions on the leaves, twigs, and clementine mandarin, you’re most likely dealing with citrus canker. When the lesions first show up, the skin around them turns yellow. In time, it turns brown and collapses in. Prevent the cankers by keeping the trees clean and dry. Use a copper fungicide to remove existing lesions.
Frequently Asked Questions
Q: Can you grow a clementine tree indoors?
A: Yes! As long as you have a sunny window, these trees make excellent houseplants. You can even find dwarf varieties that are well-suited for indoor growth.
Q: How long does it take a clementine tree to produce fruit?
A: They usually start producing at 2-3 years old.
Q: Do mandarins grow in the United States?
A: Yes, a large variety of mandarins are grown in the southern growing zones.
