Q: The fruit on my Nagami kumquat this year is variable and somewhat bland. Larger fruit have little to no acidity and can even be mealy, while smaller fruit are closer in tartness to previous years. Is this a result of weather?
A: Exposure to freezing temperatures can cause icky, mealy citrus fruit. Kumquats are relatively cold tolerant (for a citrus), but if the fruit is exposed to freezing temperatures, the skin can crack and leave you with a dry, mealy, bland crop. The larger fruit contain more water, so they are more likely to crack and dry out.
Keep in mind that these cracks may not be visible when you harvest the fruit, but they are still enough to ruin your crop.
Q: I have a mature dwarf tangerine tree in my backyard. It has flourished and produced very well over the last 20 years or so. Now, it is not doing so well. Leaves are fading in color from green to yellow and are dropping. The bark on the trunk is wrinkling and pieces are falling off. It gets plenty of water and sunshine. Also, it seems to be a home for a great number of ants. What is going on and is there hope?
A: Your tangerine may be suffering from any number of maladies. The presence of ants indicates the presence of either aphids or scale insects. Usually these are minor nuisance insects, but in great numbers they can weaken a tree. The peeling bark could be caused by insects, irregular watering, sun/wind damage or exocortis (an uncommon viral disease).
I recommend applying fertilizer especially formulated for citrus. Yellowing leaves are a common symptom of nutrient deficiency (especially nitrogen). Citrus trees require regular feeding, so this is a good place to start.
If you suspect sun damage (this is likely if the damage is on the south or west facing side), paint the trunk with white latex paint that has been diluted 1:1 with water.
Q: When is the best time to prune a grapefruit tree?
A: Most citrus does not require extensive pruning. At any time you can remove dead branches, water sprouts (long, nonproductive, extremely vigorous branches that grow straight up) and branches that are rubbing together.
If you want to prune to keep the tree’s height under control, do so either right before it blooms or after fruit set. Pruning encourages new growth, which is susceptible to frost damage, so avoid doing it late in the year. Lower branches can be pruned to improve access to fruit.
Q: After the rain, I found all these mounds in the ground. Do you have any idea what they are?
A: Your photo shows a bunch of 1/4-1/2-inch diameter holes next to little piles of excavated soil. These are earthworm holes, and they often appear after heavy rain. Earthworms produce tunnels beneath the soil surface as they feed on decaying organic matter. When the soil becomes waterlogged, these tunnels begin to collapse and the worms migrate upwards to escape. As they make their way to the surface, they re-dig these tunnels and the displaced soil ends up outside.
This is one case where holes in the ground are a good thing!
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