Citrus Seed Storage: Tips On Harvesting Seeds From Citrus Fruits

Citrus Seed Storage: Tips On Harvesting Seeds From Citrus Fruits

There is very little quite as satisfying as propagating your own fruit or veggies. Not everything can be started via seed, though. Is growing citrus by seed a possibility? Let’s find out.

Citrus Tree Seeds

There is something exciting about starting with just a tiny seed and watching the plant grow to fruition. In the case of citrus tree seeds, it must be noted that the seed you plant from say, a Valencia orange, will not have the same qualities as the original orange tree. This is because commercial fruit trees are composed of two distinct parts.

The root system and lower trunk are composed of rootstock, or stock. The scion is engendered by inserting the tissue of the desired citrus into the rootstock. This allows the commercial citrus grower to manipulate the characteristics of the fruit, selecting only those traits that are most desirable, hence marketable, in the fruit. Some of these may be pest and disease resistance, soil or drought tolerance, yield and size of fruit, and even an ability to withstand cold temperatures.

In fact, commercial citrus is usually composed of not only the above, but grafting and budding techniques as well.

What this means to home grower is that, yes, it is possible for citrus seed removal to result in a tree, but it may not be true to the original fruit. Certified, true to type, disease free propagation wood or seed is difficult to get, since it is usually sold in bulk quantities which are unsuitable for the home gardener. Experimenting with store bought citrus or that from a relative or neighbor is the best bet when growing citrus by seed.

Harvesting Seeds from Citrus

Harvesting seeds from citrus is fairly simple. Begin by obtaining a couple of the fruits you wish to propagate. This is to increase the chance of getting seedlings. Carefully remove the seeds from the citrus fruit, taking care not to damage the seeds and squeezing them out gently.

Rinse the seeds in water to separate them from the pulp and remove the sugar that clings to them; sugar encourages fungal growth and will jeopardize potential seedlings. Place them on a paper towel. Sort out the largest seeds; those which are more white than tan with a shriveled outer skin are the most viable. You may now plant the seeds or prepare them for citrus seed storage.

To store the citrus seeds, place them on a moist paper towel. Keep about three times the amount of seeds that you want to plant in case some of them are not viable. Wrap the seeds in the damp towel and place them inside a sealable plastic bag. Place the bag in the refrigerator. Citrus seed storage in the fridge will last for several days to several months. Unlike other seeds, citrus seeds need to stay moist. If they dry out, it is very likely they will not germinate.

Growing Citrus by Seed

Plant your citrus seeds ½-inch (1.3 cm.) deep in nutrient rich soil or sprout them right on a moist paper towel. Start the seeds indoors in a warm, sunny area. Moisten the soil a bit and cover the top of the planting container with plastic wrap to aid in heat and moisture retention. Continue to keep the soil moist, not sodden. Be sure the container has drainage holes to let excess water drain away.

Good luck and be patient. Citrus started from seeds will take many years to reach a maturity for fruiting. For instance, lemon trees started from seed will take up to 15 years to produce lemons.

How to Germinate Orange Seeds

Last Updated: February 19, 2020 References Approved

This article was co-authored by Andrew Carberry, MPH. Andrew Carberry has been working in food systems since 2008. He has a Masters in Public Health Nutrition and Public Health Planning and Administration from the University of Tennessee-Knoxville.

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Orange trees are a beautiful tree to have growing in your home or backyard. Not only do they produce wonderful smelling leaves, but mature trees also bear fruit. Orange seeds are quite easy to germinate, but a tree grown from an orange seed can take anywhere from seven to 15 years to bear fruit. If you're looking for a tree that will produce fruit faster, you're better off getting a grafted tree from a nursery. But if you're looking for a fun project and want to grow a tree for your home or yard, germinating an orange seed is a fun and easy way to do it.

Planting a lemon tree

The planting of the lemon tree is an important step that influences its further development, lemon production, and lifespan.

Lemon trees are demanding trees that require well drained and rich soil to develop well.

Planting lemon tree in the ground

Planting lemon trees in the ground is possible only in mild-wintered areas. They are vulnerable to freezing and need temperatures that never drop below 41 to 44°F (5 to 7°C) in winter.

  • Plant your lemon tree preferably in spring, after the last frost spells.
  • Choose a sheltered spot well-endowed with sunlight to support its growth and produce nice lemons.
  • Dig a hole about 3 times as deep and wide as the soil clump is.
  • Place a drainage layer at the bottom of the hole with gravel or clay pebbles.
  • Mix garden soil with planting soil mix.
  • Fill the hole in with this mix and press it down.
  • Water and press down again.

After that, it will be necessary to water regularly over the 2 first years, but not too much so that roots don’t get flooded.

Potted lemon tree

If it freezes in your area, try to grow them in pots with shelter for winter.

Lemon trees can’t survive indoors in winter, so they will need an outside unheated greenhouse, or horticultural fleece if the climate stays mild enough.

  • Growing potted trees is best for all your citrus if ever it freezes in your area.
  • You’ll have to bring them indoors from October to May.
  • Re-pot upon purchasing and then every 2 or 3 years in spring.
  • For larger pots, topdressing is easier.
  • For more advice on growing potted lemon treesfollow this link.

Soil mixes

Use a good-quality, lightweight planting mix formulated for containers. Look for inorganic ingredients, such as perlite and vermiculite, that will provide long-term drainage and aeration. Larger-sized particles, such as pine or other wood chips and shavings, peat moss, coir, coconut husk chips and/or coarse sand also help promote drainage and aeration around the root system. Mixes that contain all organic matter or have uniformly fine particles, on the other hand, will decompose and compact quickly, reducing aeration, which is bad for roots. If necessary, amend such mixes by 1/3 to 1/2 with the above-mentioned materials. Avoid mixes that contain chemical wetting agents, which may encourage soil conditions to remain overly moist.

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Materials and Methods

All fruit were collected from trees growing at the Citrus Research and Education Center in Lake Alfred, FL. Seeds from two grapefruit cultivars, Duncan and Flame (Citrus paradisi Macf.), and the sweet orange cultivar Hamlin (Citrus sinensis L. Osbeck) were used in this study. An effort was made to pick fruit similar in size and color. The seeds were extracted immediately after fruit harvest. All fruit were sampled on a monthly basis during the harvesting season. ‘Flame’ was sampled at eight monthly intervals: September to April ‘Duncan’ was sampled nine times: October to June and ‘Hamlin’ were sampled seven times: December to June. Fruit were considered to be of inappropriate quality when precocious germination was observed in the grapefruits (Fig. 1) or fruits had begun to fall off the tree in ‘Hamlin’ sweet orange.

Vivipary in ‘Duncan’ grapefruit.

‘Duncan’ and ‘Hamlin’ seeds collected during the first month (October for ‘Duncan’ and December for ‘Hamlin’) were divided into three batches. The first batch of seeds was surface-sterilized by keeping them for 10 min in water maintained at 52 °C (Bridges and Youtsey, 1966 Klotz et al., 1960) and dipping them in 1% 8-hydroxyquinoline (8HQ) sulfate for 3 min (Klotz, 1978). Seeds were then air-dried and stored in plastic petri dishes at 4 °C for 10 weeks. The second batch of seeds was also disinfested in warm water and 8HQ, air-dried, packaged, but later stored at room temperature (25 ± 2 °C) for 4 weeks. The third batch of seeds was peeled and surface-sterilized by shaking for 15 min in a 20% solution of commercial bleach (percent hypochlorite) and rinsed with sterile water three times (10 min each rinse). Seeds from the first two batches were subsequently processed as the third batch of seeds. For all other collection periods except the first, seeds of all three cultivars were peeled, surface-sterilized in bleach, and planted immediately. Two peeled seeds were placed per glass tube containing 18 mL of solid Murashige and Skoog medium. The tubes were sealed with Nescofilm and left in the dark at room temperature (25 ± 4 °C) for 4 weeks. During this period, seedlings germinated from the seeds and grew to be 10 to 12 cm long. The seedlings were exposed to white light for an additional 5 d before they were used for transformation experiments and germination percentage recorded for each population. The effect of 7-d chilling on seed germination was tested for the first 5 months of the picking season.

Moisture content measurements.

Seed moisture content was determined by a low constant temperature oven method for tree seeds as described by the International Seed Testing Association (1993) and expressed on a fresh weight basis.

Statistical analyses.

Seed germination percentages were averaged for the study period and are presented with sd s. Before they were statistically analyzed, values for germination were converted into different values through arcsine transformation. Significant differences among treatments were analyzed using Duncan’s multiple range test at P Table 1.

Seed germination in ‘Flame’ and ‘Duncan’ grapefruit and ‘Hamlin’ sweet orange. z

Seed germination in ‘Duncan’ grapefruit and ‘Hamlin’ sweet orange after storage of the seeds at 4 °C. z

The differences observed between the average germination percentage of grapefruit and sweet orange seeds were small but statistically significant, suggesting an important distinction in mechanisms controlling germination in these two species. Germination differences between citrus cultivars have been previously reported. Sour orange seeds were observed to have a lower germination percentage than grapefruit seeds (Fucik, 1974, 1978). We observed vivipary in ≈25% of the grapefruit seeds by the end of the picking season (May and June Fig. 1). This did not affect the in vitro viability of the remaining seeds and their ability to germinate. Earlier studies have followed and correlated maturation of seeds and their germination in the early parts of the season. On maturing in September, seeds of both ‘Red Blush’ grapefruit and sour orange were ≈330 mg and 125 mg, respectively. At that time, seeds of these two cultivars also reached the maximum germination percentage (Fucik, 1974, 1978). Our study confirms previous reports and shows that once seeds reach maturity, their viability remains high and almost constant throughout the whole harvesting season.

Seed moisture content also varied slightly throughout the season (Fig. 2). Moisture content ranged from a high of 65.1% ± 3.7% in November to 57.0% ± 2.6% in February for ‘Duncan’ and 66.9% ± 3.3% in January to 59.0% ± 5.4% in June for ‘Hamlin’ (Fig. 2A). There was also no significant variation in the moisture content in either ‘Duncan’ or ‘Hamlin’ seeds treated with 8HQ and subsequently stored at 4 °C for 10 weeks (Fig. 2B). Moisture content ranged from 64.2% ± 4.1% at the start of the experiment to 66.0% ± 3.0% at the end of the experiment for ‘Duncan’ and from 65.1% ± 3.5% to 63.0% ± 3.0% for ‘Hamlin’. Similarly, after storage at room temperature for 4 weeks, moisture content ranged from 64.2% ± 4.3% to 61.2% ± 2.9% for ‘Duncan’ and 65.1% ± 3.3% to 62.6% ± 2.9% for ‘Hamlin’ (Fig. 2C).

Moisture content of citrus seeds: (A) freshly harvested seeds, treated with 8-hydroxyquinoline (B) seeds stored at 4 °C and (C) seeds stored at room temperature. Vertical bars represent ± se .

Citrus seed moisture content has been correlated with seed germination with lower moisture levels being inhibitory for seed germination (Hassanein and Azooz, 2003). This happens when excessive desiccation disrupts cell membranes causing solute leakage from the cells (Powell and Matthews, 1980). When such seeds with damaged internal tissue are placed under conditions favorable for germination, they will not germinate. In both grapefruits and sweet oranges, higher moisture content in the seeds reduces their storage life. Storage of these seeds is therefore recommended at low humidity conditions. On the other hand, seeds do not germinate if moisture content is reduced to less than 6%. The moisture content of ‘Duncan’ and ‘Hamlin’ seeds used in our study decreased slightly as the season progressed but stayed at levels that were high enough not to affect germination. According to Ferreira (1969), germination of citrus seeds is delayed because they are dried for a longer time. The viability of citrus rootstock seeds is also reduced with prolonged drying (Nauer, 1981). Similar results have also been observed in studies with seeds of Citrus ladanifer (Perez-Garcia, 1997). Citrus seeds have also been reported to possess recalcitrant storage behavior (King and Roberts, 1980). It has been shown that seeds of several species can survive considerable desiccation, but, nevertheless, do not show strictly orthodox seed storage behavior (Ellis et al., 1990 Hong and Ellis, 1990). The storage behavior of seeds used in our study (Fig. 2) did not follow the pattern as defined for orthodox or recalcitrant seeds (Roberts, 1973). Therefore, such behavior can be described as intermediate, similar to one that occurs in Coffea sp. (Ellis et al., 1990). The appearance of vivipary in grapefruit seeds that we observed at the end of the season is a physiological manifestation of the change of hormone balance in fruit. To a high extent, vivipary is controlled by the slow decrease of abscisic acid (ABA) levels in seeds (Farnsworth, 2000). Thus, our data suggest that the change in ABA levels in older seeds did not affect their subsequent germination in vitro. Another possibility is that ABA levels did not change in seeds that did not germinate within the fruit.

When epicotyl segments derived from in vitro seedlings of these three cultivars were used in experiments for Agrobacterium-mediated transgenic plant production, their ability to produce shoots as well as incorporate our gene of interest after transformation varied according to the cultivar (Orbović et al., 2011). The shoot morphogenesis capacity also changed significantly for all three cultivars during the picking season. Responsiveness of explants to hormones supplied exogenously as components of tissue culture media is related to physiological state and hormonal balance within the seedlings. Because those seedlings germinated from seeds treated the same way as those in experiments presented here, our results suggest that the hormones mediating seed germination are different from those rendering the tissue capable for shoot morphogenesis.

We can conclude that seed viability and germination percentage for ‘Duncan’, ‘Flame’, and ‘Hamlin’ cultivars remain high throughout the harvest season. Properly treated seeds of these cultivars can be stored at 4 °C for a period of 10 weeks without any adverse effect. Stored seeds should be amenable to any experimentation during this period.

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