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Lemon tree pruning questions

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).

Saving water for outdoor plants

Dear Garden Guru,

I am saving the rinse water from the washing machine to water the potted plants. What effect will that have on the outdoor potted plants?

John in Bay Area

Hi John,

Dear John,

The rinse water from the washer is fine for potted plants as long as you are using a biodegradable detergent. Liquid detergents are better than powders. Avoid any that contain chlorine bleach, boron/borax, and any ingredient with the word sodium in its name. Also, if your water is softened, it contains salt.

The one concern with greywater is that you can get a build up of harmful salts if you use it on the same plants or the same area repeatedly. We recommend saving and using the rinse water, versus the wash water, because it will contain more dilute amounts of soap.

Container flower recommendations

Dear Garden Guru,

We just moved from the east coast. What container flowers/plants do you recommend for a west facing deck?

Karen in SF

Hi Karen,

aeonium_arborescens_tip_top-jpgWelcome to the Bay Area and away from east coast winters. The only issue is what you can’t put into containers. There is a vast array of plants to choose from. My favorite go-to plants are succulents. I like to choose Aeoniums for height, echeverias, kalanchoe paddle plant and Crassula for a bushy shape and then sedums, sempervivum, senecio and ice plants to trail over.

For color, I like to go with lavenders, salvia, kangaroo paws, agastache and lotus or calibrachoa to trail over. These are drought tolerant as well. Use a large pot and soil moist granules for less watering. An added bonus is that most of the plants for color attract hummingbirds. You can even mix the succulents with colorful plants; all like the same light and have similar watering requirements. Hope this helps.

Kiwi growing help

Dear Garden Guru,

I bought 2 kiwis (compatible male and female) three years ago and planted them in my sunny Mission district backyard. I pruned them back slightly this year as they haven't grown much and never flowered. Should I be fertilizing them? Do they need special care?

Dave in San Francisco

Hi Dave,

Good question! Kiwis can take up to 4 years to flower, sometimes up to 7 years before they get going. The wait is worth it though, Hopefully you will get flowers from both male and female plant this year for fruit production. Bear in mind the first fruit production is usually small and can take a few more years to build up to bigger yields. They are vigorous growers and can grow up to 40ft, so give plenty of room to grow in full sun. My recommendations on feeding are to top dress with Sloat Forest Mulch and feed with E.B. Stone Organics Fruit, Berry and Vine Food. I know of Kiwi vines growing in a community garden in the Soma area, and they have taken over an arbor and have produced fruit.  Hope this helps!

Meyer Lemon Tree advice

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.

How do I protect plants when temperatures drop?

Dear Garden Guru,

It's getting cold at night and some of my plants have succumbed to cold temperatures. How can I protect my plants when temperatures drop?

Sam in Albany

Hi Sam,

Protecting plants from frost can be quite easy. Twenty minutes of work on an evening when frost is expected will save many plants. The secret is having the materials you will need on hand and ready – burlap, micropore plastic (row cover sheet or weedblock), insulating blanket, shredded or bark mulch, and Cloud Cover antitranspirant.

Make sure plants are well watered. The air temperature above moist soil is about 5 degrees warmer than
over a dry soil. Spray your plants liberally with Cloud Cover. It slows the rate at which plants lose water to the surrounding air, preventing drying and wilting.

Move container plants under an eave or put them in the garage. If you choose not to move them, protect them like in-ground plants as follows: Cover the sensitive plants with a porous, lightweight covering. Freezing air flows over the cover and the unfrozen soil beneath buffers the cold. Beneath the covering, air temperatures may be 8 degrees warmer the first night of frost and 5 degrees warmer on succeeding nights. You can safely leave the covers on for one or two cool days. Remove the covers if the days warm up and re-cover at night should the threat of frost continue. If using non-porous vinyl or plastic sheeting must be supported so it does not touch the foliage (they have a tendency to supercool the plants and will freeze them.)

If you have already applied a mulch around your plants, it’s simple to heap the mulch closer to the main stem of the plant for added insulation. (Be sure to remove the added mulch from around the crown after the frost is over.)

Read our full handout on frost protection and frost recovery here.

How will the drought affect planting freesia bulbs this year ?

Dear Garden Guru,

How will the drought affect planting freesia bulbs this year ?

Rosey in San Francisco

Hi Rosey,

Freesia are actually fairly drought tolerant, originating in the arid eastern region of South Africa. What they do need is a good winter chill to set the best flowers (usually not a problem for us!). Freesia will actually begin to sprout without irrigation or rain.

Help: White flies!

Dear Garden Guru,

I have an enclosed urban (aka concrete) patio that I’ve spruced up with lots of potted plants - cherry tomatoes, herbs galore, miniature meyer lemon, potato bush, etc. The problem: My garden seems to be infested with white flies. It started on the cherry tomato, but they have spread to the basil, roses, and other plants. I have tried insecticidal soap weekly for months and seem to be losing the battle (nothing like going to get some basil and getting a cloud of white flies all over my hair and body in the process). Help! How can I save my plants from this pest?

Johanna in San Francisco

Hi Johanna,

Whitefly, as you are finding, are very difficult to get rid of.  They are immune to most sprays.  You can control the nymphs that are seen as small oval shapes on the undersides of leaves with a Neem oil spray.  The oil asphyxiates them and will do some good with repelling the adults.  You might consider putting out yellow sticky traps to reduce the populations of the adults as well as incorporate a reflective “mulch” (such as sheets of aluminum foil on the soil surface of the pots).  Your tomatoes and basil will likely stop producing by mid-November. Dispose of the plants rather than compost them.  A hand held vacuum, such as a dust buster can be used to suck the adults off the leaves when they are sluggish in the morning.

Something eating my Abutilon!

Dear Garden Guru,

My abutilon has some sort of pest. The leaves have several holes (all over the place not concentrated in center or edges). Most of the leaves are affected. I have an abutilon right next to the one with the problem and it is unaffected (though a slightly different variety of abutilon). Thoughts on what to do?

David in San Francisco

Hi David,

Sounds like Slug or Snail damage. The best way to be sure is to check at nighttime, as most leaf eating pests are nocturnal. Slugs tend to like moist shady spots, which we assume is where your Abutilon is located.

The solution is to try picking off and discarding any you see, and using Sluggo snail and slug control to eliminate the ones that come out of hiding. This is a non-toxic product that is safe to use around pets. Slugs usually die within 4 to 6 days after eating it. Sluggo lasts about 3 to 4 weeks and then breaks down as an Iron fertilizer. Reapply as needed.


Dear Garden Guru,

I have had a Brugmansia Charles Grimaldi for at least 7 years and have had numerous problems with it such as aphids, snails. etc. I have told myself that I am not giving up on the plant, but it has never flowered. Is there such a thing as a male and female tree and do you think that I am missing one of those? Help!

Julie in San Francisco

Hi Julie,

Brugmansia are very much dependent on daylight to trigger blooming. They will start to set buds when  the days start becoming shorter and nights become cooler, usually late August to September.  Also Brumansia stalks must become forked before they produce flowers. Growth below the fork is juvenile or vegetative.  Growth above the fork is considered adult or flowering.  Have you cut the plant back so that there is no fork?  Are all the stems and trunks on the plant still straight?  The plant does not require male and female.