Though rewarding, gardening is a perpetual task. Even established trees and plants may still encounter various problems each and every year that need to be addressed. Kumquat trees are popular with many gardeners for their unique fruit and pleasant blooms. Oftentimes, an older kumquat can cease to bloom unexpectedly. If your kumquat tree does just that, looking into some key factors will help you solve the problem.
Consider the Root Stock
Your first consideration with any sudden change in a kumquat tree is source reliability and the type of changes that have occurred. Kumquats are often lumped in with the citrus family, but are technically members of the Fortunella family, according to the Purdue University Horticultural Department. Additionally, they state, "Kumquats are rarely grown from seed as they do not do well on their own roots." Kumquats are typically grafted onto citrus root stocks for growth. This can lead to problems if a tree is obtained from an unreliable source. Over several years, the root stock takes on qualities of the grafted varietal. This transition is usually accompanied by change in leaf shape, fruit quality, and blooming patterns. If your tree has not experienced several of these changes, or is more than five years old, you can rule this cause out.
If you are dealing with an issue of root stock to grafted plant transition, address the problem at the nursery where you got the plant.
Changes In Maintenance Schedules
Consider any changes in your maintenance schedule. Linda Drew of the College of Agriculture and Life Sciences at the University of Arizona notes that excessive nitrogen fertilizer can inhibit tree blooming. If your maintenance schedule has been unchanged for several seasons in a row, you can rule this possibility out. However, if you have changed fertilizer types or amounts, or transplanted the tree into poorly draining soil, you could have a problem with nitrogen build-up. Also examine your pruning techniques, or lack thereof. Pruning too late in the spring can adversely impact new growth, whereas a lack of pruning can reduce vitality.
If you've changed fertilizing methods, or transplanted the tree, perform a soil test to see if any amendments need to be made. Pruning will stimulate the tree, and shifting pruning tasks from spring to mid-fall will ensure that you don't mistakenly retard new growth.
Changes In Weather
There are several varietals of kumquat trees, and each has a slightly different hardiness scale. The Nagami kumquat, according to the PU Horticultural Department, is hardy to 10 to 15 degrees Fahrenheit, while other varietals are more similar to citrus in requiring warmer temperatures to survive. If you reside in a region where winter temperatures are usually hospitable to your kumquat species, think back to when the problem began and the weather patterns that preceded poor or absent blooms. If it was unusually cold, or there were particularly late frosts, Rod McKusick---also at the College of Agriculture and Life Sciences at the University of Arizona---points out that a late frost, or a particularly cold frost, can damage the kumquat tree and potentially inhibit blooming.
Take preventive measures against frost damage in winter and early spring. Cover the tree in such cases, or bring the plant inside.