What to do if your Meyer lemons don't ripen and turn yellow
Q. I have a Meyer lemon tree that has been covered with fruit for months, but none of it is turning yellow. The fruit look to be mature size, but they're still dark green.
I usually pick my lemons before we get a hard freeze, which is typically in early November. My lemons are usually yellow by now. Recently, my tree has started to bloom.
I have two questions: Is there something wrong with my tree that the fruit is not turning yellow and it is blooming? Can I harvest the lemons even if they have not turned yellow?
A. The blooms are normal, as lemons will flower and fruit more than once per year if conditions are favorable.
The reason your fruit has not turned yellow this early in the season is that we have not had enough cold weather to encourage the loss of chlorophyll — green pigment — and the increase of carotenoids — yellow/orange pigment — in the fruit. This occurs naturally as the fruit ripens, but cold weather speeds up the process. Meyer lemons typically ripen November through March in our climate.
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Unlike other citrus, where we need the cold temperatures to add sweetness to the fruit, we cherish lemons for their acid. With oranges and mandarins, we need a few weeks of cold weather to not only help the fruit turn orange but to increase the sugar content in the fruit.
So as long as the green fruit is at least two to three inches long and beginning to soften a bit as it adds juices, it should be okay to pick it green. The fruit is usable at any stage past dark green but will have a stronger acid flavor if you pick them before fully ripe.
That said, the Meyer lemon is a cross between an orange and a lemon and is known for its milder taste, so if you pick it green, it will be more acidic in taste then your typical Meyer lemon and you may be disappointed. Meyer lemons don't ripen any further once picked, so if it's the milder taste you want, then it's best to leave the fruit on the tree as long as possible.
It's a good idea to pick fruit before a hard freeze if it's ripe. When citrus fruit freezes, it can become pithy and lose its juiciness.
However, you should be able to keep the fruit from freezing by protecting your tree and the fruit by covering it with a blanket or heavy tarp on those nights where it's predicted to dip below freezing. Don’t use plastic as a tarp; it does not provide enough insulation against the cold. You can build a tripod of light lumber, bamboo or PVC pipe around the tree and cover it with frost cloth or tarps on the coldest of nights.
If the tree is small enough, just wrap the cloth around it, making sure the cloth goes all the way to the ground. Don’t forget to unwrap the tree during the day.
For more information on growing citrus in colder climates, check out the University of California Cooperative extension publication “Growing Citrus in the Sierra Nevada Foothills” by Cindy Fake at bit.ly/3NbC5uG.
The Shasta Master Gardeners Program can be reached by phone at 530-242-2219 or email email@example.com. The gardener office is staffed by volunteers trained by the University of California to answer gardeners' questions using information based on scientific research.