My parents have a kumquat tree and it recently seemed to have delayed fruiting, so we looked to some reasons that could be causing it. While we came across many possible causes, there were a few that were recurring and made the most sense. Here’s what we found.
The best ways to encourage a kumquat tree to fruit are to provide proper sunlight, watering, nutrients, and pollination. Also, allow the tree to reach full maturity and to check the fruiting season. Keeping two or more kumquat trees increases the fruit size and yield, and reduces dropped fruit.
Let’s take a closer look at how you can get your kumquat tree to fruit.
1. Let It Mature
It may seem basic, but sometimes your kumquat tree just needs more time to produce fruit. Plants often need to reach a certain level of maturity before they start to flower.
Kumquats will start to bear fruit in as little as 2-3 years if they’re grafted, or as long as 15 years if they’re grown from seed. If you have a kumquat tree that hasn’t fruited yet, it could very likely be that it’s too young. For quickest results, opt for a grafted kumquat tree over one grown from seed.
The amount of time for a kumquat tree to mature varies depending on whether the tree was grafted or grew from a seed. Grafting the bud of a younger tree to an already mature rootstock lessens the amount of time required to reach fruit-bearing age.
This process also helps guarantee that you can still get blossoms even on a small plant.
Also, recently transplanted trees will often focus on growing roots instead of producing fruit. This can take anywhere from 3-5 years after being relocated before the root system is matured enough to start to grow fruits.
One strategy to speed up fruiting is to prune some branches to encourage the tree to focus on fruit production instead of growing foliage. This also helps prevent leaves from crowding airflow around the tree which can discourage flowering.
However, it is possible to over-prune kumquat trees. If you prune too much, all of the energy from the tree will be focused on leaf regeneration in efforts to survive.
2. Check The Fruiting Season
Kumquat trees bloom in the early summer and their fruits ripen sometime between December to March. If your tree isn’t getting flowers, check its sunlight, watering, and nutrients. If the tree isn’t mature enough, or stressed, it won’t produce flowers.
Generally, kumquat trees need at least six hours of full and direct sunlight to produce flowers.
3. Water Properly
While it seems simple, avoiding over or under-watering your kumquat tree can be a difficult balance. Ideally, the soil should be moist, but not soaking wet.
Generally, young sprouts should be watered a couple of times per week, but mature plants don’t need to be tended as often.
A good way to check if your plant needs to be watered is to stick a finger in the first 2-4 inches of soil and to see if it is still damp. Wait until the soil is dry to water again.
Additionally, kumquat trees thrive in humid environments, so if your plant is indoors try misting the leaves to prevent them from drying out and curling.
Also, check that the soil is well-drained. For indoor trees, this can be done by choosing a pot with good drainage. For outdoor trees, be sure to not use clay-like soils that aren’t capable of draining.
Clay soil will keep the plant sitting in water and will result in root rot. One way to check if your soil drains well is by doing a drainage test. This is done by digging a 1-foot by 1-foot hole and filling it with water. If the hole drains slower than 2 inches per hour, it has poor drainage.
Overall, the best way to water citrus is by deep-watering. Deep-watering is the process of providing more water in less frequent intervals. This trains the kumquat tree to grow longer roots and become more drought-resistant. It also means you don’t have to water as often, so it’s a win-win!
4. Provide Balanced Nutrients
Kumquat trees need the appropriate nutrients to root, leaf, flower, and grow fruit. For kumquats, and most citrus trees, the most critical nutrients are nitrogen, magnesium, phosphorus, and potassium.
One way to tell if your plant is receiving the proper amount of nutrients is to study the leaves.
Pale foliage usually means a lack of nitrogen, and yellow leaves can suggest a wide number of issues.
Chlorosis, or yellow leaves with green veins, often means that your kumquat tree needs more zinc.
And yellow leaves starting at the top of the tree instead of the bottom usually implies a lack of potassium, iron, or magnesium.
Lastly, know that zinc is necessary in small amounts to help produce chlorophyll and enable photosynthesis. Enough zinc can usually be provided through the soil that your tree is planted in.
If you believe your kumquat tree is lacking nutrients, try using a complete, organic citrus fertilizer or quality compost. However, since compost has a neutral pH, you may need to mix in some coffee grounds, sand, or peat moss to increase the acidity slightly).
Keeping a properly balanced pH is also necessary for proper fruiting on Kumquat trees. Like most citrus trees, kumquat trees can be planted in soils with a wide range of pH values. However, slightly acidic soil with a pH of around 6-7 is the best balance for kumquat trees.
At too high or too low pH values, most of the nutrients are less available to the tree. In fact, higher acidic soils can reach toxic levels of nutrients.
A well-balanced pH in the soil provides the right amount of nutrients to support growth and fruiting.
If you’d like a recommendation of which fertilizer to use for your kumquat tree, check out my recommended fruit tree fertilizer page.
5. Increase Pollination
Kumquat trees are self-pollinating, so they don’t need another citrus tree nearby to produce fruit. However, they can still benefit from cross-pollination, which increases the amount and size of the pollinated flowers and fruits.
You can increase cross-pollination by planting companion plants, beekeeping, or manually pollinating (with a clean q-tip, toothbrush, or paintbrush).
Pollinators such as bees, birds, and butterflies, carry the pollen from male to female flowers. Without pollination, the tree will flower but won’t produce kumquats.
Sometimes outdoor kumquat trees still don’t get enough pollination. One way to increase the likelihood of fruit production is to plant flowers in your garden. This can help attract more pollinators to the kumquat tree’s vicinity and increase pollination levels.
Additionally, planting more citrus for improved cross-pollination can help, but it’s not necessary.
Although rare, some kumquat trees might need to be pollinated by hand to trigger fruit production. This can be done with a toothbrush or a paintbrush.
When you move the brush around the center of each flower around the plant, you are acting as the pollinator.
To learn more about pollination, and how to improve it for your citrus trees (including kumquats), check out my post on citrus tree pollination.
To recap, the top five reasons for a lack of kumquat fruit production are:
Whether you’re growing your kumquat tree inside in a pot or outdoors in a garden, these factors can greatly affect your tree’s growth and fruiting ability.
Provide 6+ hours of sunlight, only water when the top 2-4 inches of soil is dry, provide a balanced fertilizer, and increase pollination when you can.
Following these best practices will give your kumquat trees the best chance of flowering and fruiting!
Want to grow more kumquat trees but don’t have space for a garden? Try growing kumquats in containers using this tutorial from Epic Gardening.