How to Propagate a Mandarin Tree from Cuttings, Seeds, Air Layering, and Grafting

Composition of a Citrus Tree

A commercial citrus tree usually consists of two parts: the scion and the rootstock. The scion is the above-ground portion of the tree and comprises the main trunk, limbs, leaves, and fruit. Rootstock, also written as “stock,” is the part of the tree that has the lower trunk and the tree’s roots. Rootstocks are usually grown from seeds, but can also be grown from cuttings or tissue culture. Grafting, also known as budding, is the process by which the scion is joined to the rootstock. We’ll talk more about this below. By using different cultivars for rootstock and scion, more desirable characteristics can be incorporated into one single tree. A certain cultivar for the rootstock can make a citrus tree resistant to a number of stresses, including poor soil conditions, pests and diseases that come from the soil, and cold weather. Rootstock can also greatly influence the size, fruit quality, and yield of a citrus tree. More information on rootstock selection can be found in the Citrus Rootstock Selection Guide (https://edis. ifas. ufl. edu/publication/hs1260). The choice of scion depends on the growers preference and desired economic value of the cultivar.

It is the art and science of plant propagation to make more plants while keeping their unique traits from one generation to the next. Grafting is a specific way to grow plants. It involves putting a piece of one plant (called a scion) into another plant (called a rootstock or stock) so that they grow together as one plant. When you budding a tree, the scion is made up of a single bud attached to a piece of bark and sometimes a thin slice of wood underneath. This is the best way to spread young citrus trees because it works well for them and doesn’t require as much skill as other types of grafting. There are different kinds of buds, but the inverted T bud and the chip bud (hanging bud) are the ones that are most often used for citrus in Florida.

To change the cultivar of an existing citrus tree, a procedure known as top-working may be used. This involves grafting a new cultivar onto the existing scion. Several grafting procedures (including T budding) can be used to top-work citrus, but some require considerable skill.

Citrus rootstock seeds often have more than one embryo and make nucellar embryos. These embryos come from the mother plant tissue (the nucellus) that surrounds the embryo sac. This event is necessary for rootstock production because seedlings that come from nucellar embryos will have the same genes as the mother plant. In few cases, seedlings will grow from the zygotic embryo of the seed. These plants, which are called “off types,” need to be rogued because they often don’t grow as well and have different genes. Sometimes, the seeds will only or mostly make zygotic embryos. In this case, the rootstock will need to be spread through other means, like tissue culture or cuttings (see next paragraph). More information on citrus rootstock propagation can be found in the Citrus Nursery Production Guide, chapter 6 (https://edis. ifas. ufl. edu/publication/hs1329).

Even though citrus fruit seeds will eventually grow into trees that bear fruit, fruit production usually doesn’t happen for a long time because the trees are still young. Most citrus cultivars used as rootstocks don’t produce fruit that can be eaten; the fruit is only used to make more plants.

Seeds can be purchased or extracted from mature citrus fruit. In order to keep any possible disease agents from getting into the fruit, it should be rinsed in 20% diluted sodium hypochlorite (bleach) before the seeds are extracted. In addition, seeds should be disinfected, followed by a thorough rinse with water. After the seeds are extracted, any fruit tissue that is still stuck to them can be washed off with diluted potassium hydroxide or left to sit overnight with the enzyme pectinase. The seeds should be rinsed and then spread out evenly on aluminum foil or non-stick paper. They should be dried completely without being in direct sunlight. You can plant seeds right away, but it’s not a good idea because they usually need time to dry out before they can germinate properly. Dried seeds should be placed in polyethylene bags and stored at 40–45°F (4–10°C). For long-term storage seeds should be treated with a fungicide. Plant seeds 1/4 to 1/2 inch deep in pots or flats that are the right size and have sterile potting mix in them. Taking off the seed coats or soaking the seeds in water with oxygen for eight hours before planting can shorten the time it takes for the seeds to germinate and grow into seedlings. If there is enough water, sunlight, and warm soil, emergence will happen two to three weeks after planting (Figure 1). Plants should be trained to a single stem (no branches within 6–8 inches of the soil).

To connect the desired scion cultivar to the rootstock, you need to get budwood from disease-free, healthy trees that have been certified by the Department of Plant Industry (Figure 2). When seedling stems are 1/4 to 3/8 inch across (about the size of a pencil), they are usually ready to bloom. When the rootstock is actively growing and the bark is slipping (the bark easily separates from the wood underneath), which can happen from April to November depending on where you live, you can budding. It is important to keep the stock plants (the rootstock liners) well-watered and fertilized prior to budding. The area to be budded should be pruned clean of thorns and twigs. The preferred budding height is 6–8 inches above the base of the stem.

Most of the time, budwood is taken from twigs from the next-to-last growth flush (the wood behind the current growth flush) or from the current growth flush after it has started to firm up. As is often the case with young wood, budwood should be round and not too angular. It should also be mostly straight and have well-formed buds in the leaf axils. Whenever possible, budwood should be approximately the same diameter as the rootstock stem to be budded.

When cutting budwood from a tree, the unwanted wood and/or growth flush should be thrown away. The remaining budwood should then be cut into 8- to 10-inch lengths (Figure 3). To protect the bud, the leaves should be cut off leaving a short piece of the petiole about 1/8 inch long. Trimmed budsticks should be labelled as to cultivar, date, and budwood source. Budwood can be kept in the fridge for one to two weeks after being wrapped in polyethylene bags, but it should be used as soon as possible.

Because of the risk of introducing serious virus or virus-like diseases, the Citrus Budwood Protection Program, first established in 1957, became mandatory in 1997. Therefore, all propagations of citrus in Florida require the use of budwood from certified disease-free nursery stock in compliance with rule 5B-62, F.A.C (https://www.fdacs.gov/ezs3download/download/25182/516098/Citrus-Nursery-Stock-Certification-Manual-02-14-13.pdf).

A very sharp budding knife is the most important tool for successful budding. You can find these at specialty stores or garden supply stores (Figure 4). To make sure that the scion and rootstock can touch smoothly while they heal, the cut must be clean and smooth. A sharpening stone and honing oil are also needed to keep the blade from getting dull over time. The purchase of a diamond sharpening stone will eliminate the need for use of oil. Polyethylene budding tape, which comes in clear or green, is used to cover buds to keep them from drying out and help them join together. Using clear tape allows for observation of the bud union during the healing process.

T budding is a relatively simple procedure and is recommended over chip budding, which requires more expertise. The inverted T bud method is used to grow most Florida citrus trees, but the standard (upright) T bud method can also be used. When the rootstock plant is the right size, its bark is slipping, and there is budwood available, budding can happen.

The blade of the budding knife should be cleaned before any cuts are made in stock or budwood to stop the spread of disease. Using the budding knife, a vertical cut of about 1. 0–1. 5 inch in length is made completely through the bark in a smooth area of the rootstock stem. Between the vertical cut (Figure 5) and the horizontal cut (Figure 6), the bark is split down the middle. The cut is made at a slightly upward angle, again cutting completely through the bark. The point of the knife can be used to lift the bark along the vertical cut. While holding the very end (tip) of the budstick away from you, a bud is taken off of it. A cut is made about 1/2 inch above the bud with the knife blade almost parallel to the axis of the budwood. A shield-shaped piece of bark and wood about 3/4 to 1 inch long with a flat, smooth-cut surface is then taken off. Only a thin sliver of wood should remain under the bark. The bud should not be scooped out because too much wood will be removed with the bud. Hold the bud shield between your thumb and the knife blade or use the leaf petiole stub as a handle to keep from touching the cut surface.

The bud should be put into the stock right away; the cut side of the bud shouldn’t be left to dry. Slide the bud shield, which is made up of the bud and its bark and wood, under the rootstock’s bark flaps so that the cut side is flat against the rootstock plant’s wood. The bud shield should be completely enclosed in the T incision (Figure 6).

Buds should be wrapped immediately following their insertion into the rootstock. Wrap buds with budding tape (polyethylene strips about 1/2 inch wide by 6–10 inches long). Start wrapping below the bud with three to four turns and end with several turns above the bud. Cover all of the bud’s exposed surfaces with tape. Alternatively, wrapping can proceed from the top down. The end of the tape is secured beneath the last circular turn. The wrap should be firm without being excessively tight. Wraps should be removed after 14–21 days and should not be left on more than 30 days. If there was a successful union between the bud and the rootstock, the bud will be green and not shrink or dry out. Callus formation should also be evident around the edge of the bud.

Chip budding takes a little more skill than T budding, and it’s usually done when the rootstock plant’s bark won’t slip or is too thick to T bud. The chip bud is cut while holding the budstick with the apical end toward the budder. A smooth cut about an inch long and just into the wood is used to remove a thin slice of wood that has a scion bud on it. A second cut is made at the top of the first cut, forming a notch. In a similar way, a chip is cut off the rootstock (Figure 7), and the scion bud is put on the cut to match the cambium. Cambial tissue is a thin layer between the bark and the wood of a tree. This is an area of active cellular growth of a tree. There are only two thin lines of cambial tissue on both the scion bud and the rootstock that can heal, so it is important that both sides are matched as much as possible. The scion should be wrapped as described for T budding so that all cut edges are completely covered.

After the wrapping is taken off and the bud and stock have joined together, the bud needs to be “forced” to grow. Plant hormones made in the top part of the rootstock seedling may stop the scion bud from growing unless the bud is forced to grow. Cut the stock about two thirds of the way through on the same side as the bud and about one to one and a half inches above it. This forces the buds to grow. Then, the seedling top is pushed over to lie on the ground; this procedure is known as lopping. Alternatively, the seedling top is bent over to form a loop in a process called bending (Figure 8). In both situations, the rootstock top will keep feeding the roots and growing scion with food and other growth aids in the early stages of scion development (Figure 9). After the scion bud has grown a few inches, cut about 1/2 inch above the scion to remove the rootstock. If cutting or bending isn’t an option, the rootstock top can be taken off by making a sloping cut through the rootstock about an inch above the scion bud. Rootstock sprouts that appear along the main stem, especially close to the scion bud, should be cut off as soon as they appear because they will slow the growth of the new scion. As the scion grows, it will need to be staked and tied down at regular times to keep it from breaking. It’s time to plant the nursery tree in the field when it’s about 18 to 20 inches tall (Figure 10). The top should be pinched out to stimulate lateral shoot development.

Other Propagation Methods for Citrus

Grafting procedures other than budding involve the use of a scion with two or more buds. There are numerous types of grafts, including whip, cleft, bridge, in-arch, stump, side, inlay bark, approach, and others. Grafting is most commonly used to repair existing trees or to top-work existing trees to change varieties.

By budding or grafting, top-working changes the top of an established tree from one cultivar to another or to more than one cultivar. Several procedures may be used when top-working citrus trees. They include bark grafting, cleft grafting, and T budding. To top-work a citrus tree by T budding, cut it back so that there are only a few branches that are 2 to 5 inches across or less. Insert 1–3 buds on the upper side of the remaining scaffold limbs using the T bud method. Remove unwanted buds and sprouts to insure that only the desired scion buds grow. If the branches are too big to make budding hard, cut them back to the main scaffold limbs and remove the whole top. Be careful: trees that have been severely pruned should be whitewashed to protect them from sunscald. Around six months after the limbs sprout back and mature a bit, the sprouts can be budded as described above, using four to six of the stronger sprouts on each limb (Figure 11).

Sometimes, nurseries don’t have enough seeds for some of the most popular rootstock varieties. To make a lot of genetically identical plants, vegetative propagation methods are needed. One common way to grow rootstocks is from cuttings. This is especially useful for citrus rootstock breeders who don’t always have access to seed source trees for their new selections. For this method, about 1-inch-long single-node cuttings are taken from the woody parts of 2–5 month-old branches of citrus plants that have been tested and proven to be disease-free. Photosynthesis takes place at the node, where the leaf stays attached so that it can reach the developing roots. The leaf can be cut down to a length of 2020%E2%80%9330% of its original size. The bottom end of each cutting is then dipped in a rooting powder that contains a hormone that helps roots grow, like indole-3-acetic acid (IAA) or naphthalene acetic acid (NAA), and put into potting medium that has already been wet (Figure 12). Plants that come from cuttings need to be kept in a moist environment so they can survive without roots. This can be accomplished by placing plants in an enclosed high-humidity environment and/or using an automated misting system. Under these conditions, a young plant will usually develop within several weeks after planting. Once cuttings have grown roots and plants have started to grow, they can be cared for in the same way that seedlings are.

Thanks to improvements in micropropagation techniques for vegetative propagation of citrus rootstocks, it is now possible to grow a lot of genetically identical plants from rootstock selections at a low cost. Starting materials for micropropagated plants can be nucellar embryos or buds, but they must both come from disease-free foundation trees. This depends on what the nursery prefers. The explants are put in an agar-nutrient medium that might have a small amount of growth regulators in it to help the plants grow back faster. After plants are grown again, they are subcultured on a new agar-nutrient medium every two weeks so that they can make more shoot clusters (Figure 13). After an elongation phase, clusters are separated into individual shoots. Then, each plant is either rooted on agar medium before being moved or rooted directly into potting medium, depending on what the nursery prefers. Following an acclimatization period in high-humidity conditions, the same care procedures can be used for young plants as for seedlings. It is common for many fruit crop systems to use tissue culture to quickly make a lot of plants that are all the same and free of disease.

Release Date:April 9, 2021

• Critical Issue: 1. Agricultural and Horticultural Enterprises

This document is HS1309, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date October 2017. Revised February 2021. Visit the EDIS website at https://edis. ifas. ufl. edu for the currently supported version of this publication.

Mongi Zekri is a multi-county citrus agent IV for UF/IFAS Extension Hendry County. Ute Albrecht is an assistant professor in the Horticultural Sciences Department at the UF/IFAS Southwest Florida Research and Education Center. Jeffrey Williamson is a professor in the Horticultural Sciences Department at UF/IFAS Extension in Gainesville, FL 32611.

PROPAGATE YOUR CITRUS TREES FROM CUTTINGS// CLONING WITH RESULTS

How to grow a mandarin tree from cuttings?

Once the cutting has established roots, it’s time to transplant it into a larger pot or outside into the ground. Make sure to choose a sunny location with well-draining soil. To grow a mandarin tree from cuttings, we need to encourage healthy growth. And to do so, make sure to fertilize the tree regularly with a balanced fertilizer.

How do you propagate a mandarin tree?

If you are able to propagate citrus in your area, there are a few different reliable methods for propagation. Methods include grafting, rooted cuttings, and seed propagation. Grafting is the most reliable way to produce a strong disease-resistant mandarin tree. There are a few different rootstocks available for mandarins.

How do you repot a mandarin tree?

Place a well-draining potting mix specifically formulated for citrus trees into the bottom of the pot. Have this at the ready. The best time to repot a mandarin tree is in early spring before new growth starts. This allows the roots to be established in the new pot before the active growing season.

How do you plant a mandarin tree?

Planting mandarins successfully requires choosing the right variety for your climate, ensuring they receive ample sunlight, and planting them in well-draining soil. Regular watering, fertilization, and pruning are key to healthy growth and abundant fruit production.