Kumquats are heavy feeders, and they need fertilizer during their active growing cycle. You don’t need to fertilize your trees in the winter months, when the trees are semi-dormant.
If you’ve just planted/potted your tree, you shouldn’t fertilize it until growth begins in the spring. You’ll want to use fertilizer formulated especially for citrus trees. Keep in mind that this fertilizer is also for much bigger citrus trees; only use half the amount of fertilizer recommended—or even less. You can also give your tree diluted liquid fertilizer, such as fish emulsion, liquid kelp, or a combination of the two. Water your tree well before and after you apply fertilizer, so you don’t burn the plant.
Fertilizing Kumquat Trees Planted Outside
In your tree’s first growing season, plan to fertilize in March, April, June, and July. Be sure to keep the fertilizer well away from the tree trunk, and spread the fertilizer in a circle about 30 inches in diameter. Each year, you’ll increase the diameter of your fertilizing area to keep up with your tree’s growth; the general rule of thumb is to fertilize an area that’s two times the diameter of your tree’s canopy. If your tree is planted in a raised bed, expand the fertilizer zone within the borders of your raised bed.
Fertilizing Kumquat Trees Planted in Containers
For a container-grown kumquat tree, you can’t fertilize beyond the tree’s canopy, since the soil has a defined boundary. But it’s still important to establish a fertilizing schedule—February, May, and August work for potted trees. Just as with an outdoor-planted tree, use a fertilizer formulated especially for citrus trees. Top-dress the soil, being sure to water before and after applying fertilizer. Don’t get any fertilizer on the tree itself—only on the soil. In the spring, a slow-release citrus fertilizer is a good choice to keep your tree healthy. As it grows, you can occasionally give it a treat of diluted liquid fertilizer, such as fish emulsion or liquid kelp.
Your potted tree isn’t going to grow as broadly or as tall as one planted in the ground, but it will grow; with that growth will come a continued need for proper nourishment. Get your fertilizing schedule on your calendar.
Do you fertilize your kumquat trees? What type of fertilizer do you use? How often do you fertilize? Please tell us exactly how and when you fertilize your kumquat trees.