Elisabeth C. Miller Library logo Miller Library Home UW Botanic Gardens Home UW Botanic Gardens Home book graphic

3501 NE 41st Street, Seattle, WA 98195 | (206) 543 0415 | Open: | Library Schedule

Gardening Answers Knowledgebase

Plant Answer Line Question

Keywords: Insecticidal soap, Citrus limon, Aphids

My Meyer lemon has aphids all over it and has lost its leaves! I just brought it inside for the winter. What can I do?

Answer:

The aphids were more than likely already there, even if not enough for you to notice, and once inside the warm(er) house they multiplied. Aphids do love citrus plants. The blossoms probably fell off due to the temperature change they experienced coming indoors.

The following information was found on p. 278 of the 2001 edition of the Sunset Western Garden Book:

Citrus in containers. Fertilize monthly from midwinter to mid-autumn with high-nitrogen liquid fertilizer, containing chelated zinc, iron, and manganese. Potted citrus ... in cold-winter regions: shelter plants in winter; a cool greenhouse is best, but a basement area or garage with good bright light is satisfactory.

Many of the common products sold in nurseries or garden centers contain the trace elements listed in the Sunset info above. Also, there are specific formulations for citrus available, also carried by many nurseries and garden centers.

...Sunset Western Garden Book continued...Citrus as houseplants. No guarantee of flowering or fruiting indoors, though plants are still appealing. 'Improved Meyer' and 'Ponderosa' lemons [other citrus names omitted] are most likely to produce good fruit. Locate no farther than 6 ft. from a sunny window, away from radiators or other heat sources. Ideal humidity level is 50 percent. Increase moisture by misting tree; also ring tree with pebble-filled trays of water. Water sparingly in winter...

I grow 2 Meyer lemons and find that they do best outside until the temperature goes down into the 20s. They are pretty hardy. The aphid problem is not a problem outside until spring. If you have a sun porch at your house, that might be a great place to put the lemon in winter.

As for the aphids, Colorado State University Extension provides information on insect control using insecticidal soap. You can purchase it or make your own: 1 teaspoon of soap (the mildest you can find) per quart of water, sprayed on both sides of the leaves and on growing surfaces.

Date 2017-05-26
Link to this record only (permalink)

Plant Answer Line Question

Keywords: Container gardening, Plant nutrients, Citrus limon, Water requirements, Fruit--Care and maintenance

I purchased a small Meyer lemon plant from a nursery in Florence, OR, and it grew, and blossomed very well, and even produced many tiny lemons - all of which have now, at this point, dropped off. The leaves are yellowing, too. It is in a good size container, in full sun. The container sits in a large saucer which does fill with rainwater. This I empty, but the plant remains wet. New blooms are coming on some of the branches, old blooms are shrivelling. No more lemons coming as yet.

My question is, why did the tiny lemons drop off? And, should the plant get overly wet? My nursery person has no information. I would appreciate any information you have.

Answer:

The following information comes from Citrus (by Lance Walheim, Ironwood Press, 1996).

It sounds as if your container has good drainage, but maybe the plant is getting too much rainwater. That might be causing the leaves to turn yellow. Another cause could be a nitrogen deficiency, which would be most visible in older leaves, which would yellow from the tip to the base.

As far as the plant's water needs, it will need water when the top two to three inches of soil become dry. Frequent watering (or excess rainwater) can leach nutrients from the soil, so the plant will need to be fertilized regularly -- once or twice a month using a liquid, high-nitrogen fertilizer that includes the micronutrients zinc, iron, and manganese.

The small lemons which drop off may not be anything to worry about, as fruit drop occurs normally as the tree varies its fruit load with its carrying capacity. Pea-sized fruit usually drop about one month after bloom. A more noticeable drop occurs in late spring to early summer, when golfball-sized fruit may drop. Other reasons for fruit drop could be conditions which limit tree growth, such as excess heat, lack of soil moisture (not relevant in your case), and fluctuating weather conditions. It is also possible that the fruit drop is due to lack of nitrogen.

Date 2017-05-17
Link to this record only (permalink)

Plant Answer Line Question

Keywords: Citrus limon, Insect pests--Control

I have a lemon tree that is actually not dead yet, but it's not looking good. I had to bring it in late last year as Florence [Italy] was due to have frost for a few days. Then we had horrendous winds and heavy rains. After a few weeks inside, (on a nice sunny indirect-light window sill) it started to drop everything: leaves, blossoms, tiny lemons, and now it is utterly bare. Maybe this is why? On clearing the leaves off the dirt I noticed little blister-like spots on some of the branches. I scraped them with my fingernail and they peeled off, but left sticky stuff behind. Is this a disease? Can I wash the stems? With what? I trimmed the tips of the tiny branches; they are green inside so not dead. I did fertilize with a high-nitrogen liquid, over the leaves and in the pot, a couple of times a month. I have a feeling that spider mites are doing the mischief. Is there hope?

Answer:

Sorry to hear of your bare lemon tree! The loss of leaves could have been a reaction to the wind, and once the leaves are gone, the tree can become susceptible to waterlogging, pests, and diseases. It is good that you moved it inside, and that it has good light. The blister-like spots on the branches sound like a kind of scale insect, to which Meyer lemons can be prone: California red scale (Aonidiella aurantii). I do not think it would be spider mites, because they would cause stippled, yellowed leaves, and might leave telltale webs. Scale can defoliate and kill a tree. There are beneficial Aphytus wasps that can be used to control scale, but they have to released regularly to be effective and, of course, you would not do this while your tree is indoors. A good reference about scale insects and how to manage them is Pests of the Garden and Small Farm by Mary Louise Flint (University of California Division of Agriculture, 1990)

Here are two recommended books on growing citrus:
Citrus: Complete Guide to Selecting & Growing More than 100 Varieties by Lance Walheim (Ironwood Press, 1996)
Success with Citrus Fruit by Sigrid Hansen-Catania (Merehurst Ltd., London: 1998)

Date 2016-12-30
Link to this record only (permalink)


Didn't find an answer to your question? Ask us directly!

Browse keywords

Search Again:

April 11 2017 13:50:16