Dear Garden Guru,

As a chef, my edible garden is very important to me. I currently hold a SE exposed patio in SOMA with good light in the absence of fog. I grow many herbs and a dwarf Meyer lemon tree. Any recommendation to increase the crop and longevity of growing delicate herbs? Also, my lemon tree shows slightly yellowing leaves. I'm guessing lack of nitrogen and other trace minerals? The tree is producing several new flowers and buds. I'm worried the small tree cannot produce or support too many whole sized, ripe fruits. Shall I prune and reduce the crop size? Cheers.

Dave in San Francisco

Hi Dave,

For herbs: you may want to plant more of what you use most. I am thinking you mean things like Basil, parsley, chive, and thyme.  To encourage herbs to resprout more quickly after a pruning, feed them with a liquid fertilizer 1/2 strength every time you harvest. I like to plant herbs in 3’s. I rotate the harvest among them and it ensures I have enough when I need it.

It is common for citrus trees to yellow up, especially over the winter. We like the Growmore Citrus Growers blend which contains all the trace elements Citrus need. You can supplement with the E.B. Stone Citrus Food to provide more nitrogen. Citrus are notorious for producing more fruits than they possibly could support. The plant will thin itself when the young fruit is the size of green peas. There is no need to prune other than to shape.

Dear Garden Guru,

I have a Meyer Lemon Tree that looks like something has been eating the leaves. Can you tell me what this could be and how to treat it?

Shirlee in Tiburon

Hi Shirlee,

I suspect your problem could be citrus leaf miner, especially at this time of year. The moth’s larvae mines through new leaves, causing them to distort and get ragged.  Read our handout about this pest: https://www.sloatgardens.com/wp-content/uploads/2015/09/citrus-leafminor.pdf  Another possibility is young snails.  Applying Sluggo or Sluggo Plus around the base of the tree may help.

Dear Garden Guru,

For several years, my lemons have had a thick rind and little juice in them. I put a Meyer lemon tree in about 20ft away and it's starting to put out lemons this year. The rind again appears a bit thick. What's missing in my soil? I am using a citrus and avocado fertilizer. AG

AG in San Francisco

Hi AG,

There are two reasons that the rinds of citrus become thick and both are nutritional. The first is overfeeding with a food high in nitrogen.  It is recommended that a basic citrus fertilizer be fed in spring and again in fall along with a supplement that contains zinc such as FST.  The second reason is a deficiency in phosphorus ( the more likely cause).  To avoid providing an excess of nitrogen, you can supplement the recommended feedings with 0-10-10.

Dear Garden Guru,

Why would lemons be dry and not juicy. It is sunlight?

Linda in San Francisco

Hi Linda,

There are a few environmental factors that will cause lemons to be dry. One is water stress. If the trees were not irrigated enough during the growing season, the tree will pull moisture out of developing fruits in order to keep the leaves healthy. Another is cold damage. When ripe or ripening lemons are exposed to freezing or frosty conditions, the moisture in the fruit dissipates. The most common reason for dry fruit is that the ripe lemons are left on the tree too long. Hope that helps!

Dear Garden Guru,

We recently moved and inherited a lemon tree that hasn't been pruned for maybe a few years. While some branches still have small, thin-pith lemons, others have reverted to grapefuit-sized thick-pith giants and the whole tree is sprouting lots of growth. When should I hack it back and how much can I prune off at one time? Do I have to wait until it’s dormant? It still has lots and lots of lemons. Thanks!

Paula in San Francisco

Hi Paula,

You can prune your lemon at any time of year to shape it. There will always be a point where some lemons will have to be sacrificed. Pruning in the fall after most of the fruit is ripened will preserve the most fruit. The larger pithy fruits are likely over-ripe and have been on the tree too long, so they should be removed. You can prune the tree as hard as you want but avoid exposing the trunk and limbs too much to avoid sunburn. Remove any growth that has thorns (juvenile foliage) or growth that is coming from below the graft (seen as a thick “collar” towards the base of the tree).

Dear Garden Guru,

I have a Meyer lemon tree the has blotchy yellowing leaves but only in one section of the tree. Could you tell me what it is and how to treat it?

James in SF

Hi James,

Your tree is showing signs of  a condition known as mesophyll collapse. It is caused by low humidity and drought conditions. It is not a disease so it cannot be treated with any spray. This is an affliction that the tree will grow out of IF a regular feeding and watering regimen begins in the spring. In addition to a citrus food fed every 6 weeks, a spring and fall supplement  of F.S.T ( iron, sulfur, zinc) will provide necessary micronutrients.

Dear Garden Guru,

Hi, I would like to buy a Meyer lemon tree in October as a gift, do you think they will be available. -Much Thanks

Dana in San Francisco

Hi Dana,

Yes, our stores will continue to stock Meyer Lemon trees throughout the Fall (Subject to availability). We sell quite a few during the entire Holiday Season, so we maintain our supply year-round. The only potential for not having them is some type of crop failure from our local suppliers.

Feel free to call ahead to your local store just to be sure. And, as always, if they are out of stock you can certainly place a “special order” for one.

Dear Garden Guru,

We have a dwarf citrus tree that I planted last winter. It is green and growing nicely. It has flowered several times, but when the fruit begins to form, it gets to the size of a ladybug and then turns black. What is happening?

Kim in San Rafael

Hi Kim,

It is normal for citrus,especially young ones, to shed small fruits. The plants always seem to set more fruit than the trees have energy to provide for. Sometimes, as much as 3/4 of the fruits will abort! Usually, the fruit will fall when still green, or it will get yellowish first.

The fact that your small fruits are turning black first indicates that you are either over watering or they are getting infected with a bacterial disease. The bacterial disease would develop in a situation where the tree was getting overhead sprinkling. It also could spread to the leaves, but you say the leaves look great. I suspect the watering more but to be sure, you may want to spray your tree with EB Stone Copper Soap. This is an organic spray that kills and prevents fungal or bacterial diseases.

I hope this helps get you started on controlling the issue. As always, feel free to visit any of our Sloat locations for more expert advice.

Dear Garden Guru,

I have a blood orange tree in a container. The first 2 years the tree produced fruit. Last year, the tree had healthy leaf growth but no flowers at all. What do you think the problem could be?

Barbara in Kentfield

Hi Barbara,

The Blood Orange does not respond well to great fluctuations in humidity. Flowers do not set well when the air is very dry. They dry up too quickly and die before being pollinated. I suspect that last year’s extremely dry weather was the cause. Other sensitive citrus such as Mandarin and Meyer lemon had the same trouble. Your tree should be getting ready to flower again this spring. Thankfully, we have had some rain and water evaporating from the soil will increase the humidity around your tree. When it is hot and dry in the spring, you may want to hose the plant down in the mornings to prevent flower loss.