Grocery Store Gardener: Grapefruit
Grapefruit was one of my first real plants that I grew on my own initiative. I was still in grade school when we had some grapefruit that had seed beginning to sprout. I couldn’t tell you today whether it was fruit that had been left in the refrigerator for a very long time or whether it was fruit that came in to the store that had already begun to sprout. Grapefruit is a commercial fruit that can be left on the tree quite some time after it ripens. This is a great way for growers to extend their picking/shipping season. Some say that the longer the fruit is allowed to remain on the tree the sweeter the fruit.
I am not sure how we came to have a grapefruit with seed that had begun to sprout. All I remember is going out to the garden to get a container of frozen soil since it was winter. This wasn’t bags of soil time especially for a country child when I was a child. I let the soil thaw and then planted the sprouting seed I had kept in a small bowl of water. I had several seed sprout. I eventually gave each a container. I know I gave some of the seedlings away. I remember that I could only keep one.
I had that grapefruit through college. When I had my first real apartment my mom made me take it with me. She was tired of caring for it for the past 4 years. It was 6 feet tall and quite impressive. Even though it was close to 20 years old it had not flowered. This is one of the problems one can encounter with seed grown plants. It is often said to take 6 to 15 years or more before a grapefruit seedling will sprout. Rooted cuttings are generally the preferred method for propagation as these produce fruit faster.
Starting from Seed
Seed propagation is probably the best alternative the vast majority of people who live in plant zones cooler than Zone 10. This zone begins about mid Florida and south or in Southern California. This means most of us will not have easy access to rooted cuttings. I’m sure some of you may wish to order from specialty nurseries. This will of course get you access to some varieties not commonly found in regular grocery stores in the north.
Still, starting a grapefruit from seed will be our mission today. I am using the seed inside of a fruit that unfortunately did not get eaten. In fact, when I realized after I had it a couple of weeks, I determined to let it “molder” on the counter until I had time to open it up. As you can see in the image it has been much longer than those couple of weeks. While my seed was not sprouting I feel the extra time in the fruit has had a chance to completely mature.
History and Cultural Considerations
Grapefruit is a natural cross between a pomelo and a standard sweet orange. It was a discovered seedling in the West Indies in the Barbados actually about the middle of the 18th Century. It was considered to be a mutation of the pomelo for many years until it was later determined to be a hybrid. Since then other mutations that have naturally occurred or induced through irradiation has led to newer cultivars. The newer versions are selected for their red fruit and how long the red color will last in a ripe fruit. Early red cultivars would fade with some age. The name came into fashion in the 19th century when other locations began planting this citrus. The fruit tends to cluster in groups which reminded these early growers of grapes.
One of the interesting things about the grapefruit hybrid is that the seed comes true. Normally a hybrid will not produce seed that mirrors the adult. Many citrus (and some other plants) produce seed that is referred to as nucellar embryony. This means that the children or seed sprout to become clones of the parent. There is always some variability that can result during embryonic production and then fertilization. It is both a strength and a weakness for plants to have this feature. The weakness is that it becomes difficult to produce new hybrids. That is what makes the grapefruit so important. It was a rare and natural (not controlled) hybrid. The strength is that there is going to be an extremely high degree of probability that the seedling that you will get from this planting will be almost 100% the same as what produced the fruit it came from.
Most grapefruit are 5-6 meters (15-nearly 20 feet) tall. They can grow larger. Since this is a smaller tree it can easily be grown with bonsai techniques. You should be able to keep these to a size that will fit in to your living room for the winter. In fact, there are some growers that live in marginal areas that grow their plants in containers so that the pot and roots can be mulched in for protection from the occasional cold weather that would normally kill the plant. The plant and pot can be tipped to lie on the ground where the soil temperature can help protect the top growth too.
Disease and Fertilization Concerns
The soil type is not terribly important for the plant to thrive. Most container grown plants are often grown in a soil-less mix. This is a porous media that allows water to freely flow through. One of the most severe problems this fruit suffers is a type of soil borne pathogen that will attack and kill the root of grapefruit. This rot is caused by a mold called a phytophthora. While this is not a fungus this type of pathogen acts and behaves in a similar manner. These pathogens tend to specialize in closely related species of plants only.
The way to discourage this is to make sure that the immediate part of your grapefruit that connects to the soil will want to be on a slight hill. You do not want to let the plant sink into the container. This situation encourages water to run towards the trunk of the grapefruit. This prevents good drainage. This stagnant moist area is just what the phytophthora need to thrive and feed on the damp root and lower trunk right at the soil line.
I still encourage regular applications of a good mychorrizae. These soil fungus promote root growth. The Tricoderma genus should still look at the phytophthora as a food source even though it is not a fungus. Click here for a bit more about mycorrhizae in an earlier hub.
Smelling is a very valuable tool for the successful gardener. I always smell plants I am working on as a normal part of my inspection. It is especially important when observing your grapefruit. Soil should have a slightly moist and sweet smell to it. If it is sour smelling then there should be concern. You may be watering more than the plant needs. The more foul the smell the more you should be concerned you need deal with a possible pathogen.
Be sure to place your plants out in full sun during the summer. You will want to slowly adjust the plant when you first take it out. The leaves that are on these evergreen plants will not be used to the strong light. It is best to place the plant in a mostly shaded location and gradually increase the light level over the course of a couple of weeks. You may have some damage anyway but the new growth you will see at the end of those two weeks will quickly replace any damaged leaves.
These plants need fertilization during the growing season at moderate intervals. It is good to start with a high nitrogen application when you first notice growth buds swelling in the spring. Shortly after the initial growth begins the plant will want to flower. The next and subsequent applications will need less nitrogen and more phosphorus and potassium. Gradually over the course of the summer you will want to reduce the nitrogen. The plant and fruit production will benefit from the bloom and root components of the fertilizer. Do not fertilize during the winter when the plant is resting.
There are some nasty thorns on this plant you may wish to cut off. Other than that, grapefruit make a superb house plant. The glossy dark green leaves give weight and stability to a room. The slightly undulating trunk and branches provide interest. You get an unusual accent all for the cost of letting your unused fruit sit and get really nasty on the counter until you can retrieve the mature seed. Don’t forget to provide supplemental lighting for the new seedlings as they will need the extra help.