Ask the Garden Guru

Our Garden Guru is on vacation. Please check back with us with your question after July 4th. Thank you!

Help with Gophers!

Dear Garden Guru,

Gophers have invaded our yard – there are holes everywhere! How does one get rid of them safely and not harm other animals and birds?

Deborah in Pacifica

Hi Deborah,

Start by using a repellent like Bonide Mole Max (it also works for gophers ).  This is a castor oil-based repellent that is not harmful to animals or birds. Take extra care to apply more heavily around holes. This granular formula is easier to apply than a liquid spray. Apply the repellent gradually towards the direction you want them to leave the property, in other words, leave them a way to get out. Applying the repellent to the whole space at once will just “trap” them there. If it is really very bad, you might consider a gopher removal/trapping service such as Smith’s Pest Management which focuses on trapping over poisoning.

Additional notes:


Squirrels in Raised Beds

Dear Garden Guru,

I have raised planter beds with steel mesh screens to keep moles and voles away, but squirrels got into my vegetable garden last summer. Do you suggest tall plant protectors that can cover a fully grown tomato plant?

Mark in Pleasant Hill

Hi Mark,

We carry larger tomato cages that will support large plants but the openings would still provide access to the ripe fruit. Some gardeners have used plastic bird netting wrapped around and over a caged tomato to protect ripening fruit from various varmints.

Squirrel deterrents

Dear Garden Guru,

Squirrels are destroying my vegetables and flowers. Does peppermint oil spray on leaves deter them?  

Robin in Pleasant Hill

Hi Robin,

Hello Robin,

Yes, peppermint oil can be effective in deterring squirrels. We carry a product from Messina specifically for squirrels called Squirrel Stopper.  The ingredients are putrefied egg, and oils of mint, rosemary, and cinnamon. It can be used on hard surfaces and perimeters as well as plants. We don’t recommend spraying this product on edible plant parts  — it’s best used as a barrier spray.

Fungus Gnats!

Dear Garden Guru,

I enjoy a window herb garden in my kitchen and every year we have a few gnats. This year there were so many more. Any advice on a safe way to address them in my home? Thanks for your help.

Claude and Ruth in the East Bay

Hi Claude and Ruth,

Fungus gnats can be controlled using beneficial nematodes. The product Pot Popper has small sachets of the nematodes designed for use in smaller indoor containers. They are simply watered in. The nematodes then prey on the gnat larvae in the soil, eliminating them. Another option for reducing the gnats is placing small, yellow sticky traps in the container. Lastly, the product Mosquito Bits which is a beneficial bacteria (Bt) is effective when sprinkled on the soil and watered in. All of these options are safe to use with edible plants and are organic controls.

Squirrels eating my Squash

Dear Garden Guru,

Squirrels destroyed my container squash plants last summer. Any suggestions for keeping them away?

Julie in Millbrae

Hi Julie,

If squirrels are a nuisance, you may have to cover your squash plantings with netting. Creating a tripod of stakes around the plants and then draping the netting should keep them out.  The netting at the base should be weighted down or secured to keep them from crawling under.  Spraying Messina Squirrel Stopper around the vegetables would be the second line of defense.

Deer and gopher tolerant flowering shrubs and fruit-bearing trees

Dear Garden Guru,

Hi - I'm looking for deer and gopher tolerant flowering shrubs and fruit-bearing trees. I have a southwest facing backyard that's very sloped. Any ideas?

Cynthia in

Hi Cynthia,

We’vee found that what deer leave alone also holds true for gophers. Here is our deer resistant plant list.

Our picks for the steep slope in full sun are: Rosemary, Lavender, Euphorbia, Oregano/Marjoram, Salvia (including culinary), Thyme, Coleonema (breath of heaven), Grevillea, and Correa.

As far as resistant trees, most fruit trees would require protection when young with some type of fencing around them. Persimmon, Olive, Pineapple guava (Feijoa), and Fig are kinds that are considered the most deer resistant. Older citrus is usually left alone but young plants are fair game, especially when other browse plants are not available.


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.

Tomato issues

Dear Garden Guru,

My tomato plants (2) were growing like mad and had many blooms. I was out of town overnight and when I returned the stems were starting to look slimy, then they quickly died, turning black. Can you tell me why?

Dolores in Pacifica

Hi Dolores,

I am sorry to hear about your tomatoes. Crop failure always hurts when it hits established presumably healthy, vigorous plants. I think that you were struck by either Late Blight of Tomato or Bacterial Blight. The sliminess suggests a Bacteria and this is a disease that can ravage a plant very rapidly. The spores are airborne or carried in the stomachs of beetles such as the Diabroitica or Cucumber Beetle (the green “ladybugs”). The disease is likely to occur if we have warm or hot days and mild nights suddenly interrupted by much cooler, damp weather.

Overhead watering will also stimulate an outbreak. I hope that you have removed the plants so that spores will not over winter in that spot. It is advisable to change the location of your tomatoes next year. To control the disease and reduce its spread, EB Stone Copper spray is recommended.

I hope this helps. Please feel free to visit any of our store locations to get more specific instructions on how to use the Copper Spray, or just get more instructions for this year.

Mealy Bugs

Dear Garden Guru,

I seem to have a mealy bug situation primarily in my succulents. I have used a fungal oil, but they seem to come back. Now what!!

Claudia in San Rafael

Hi Claudia,

It is common for succulents to get mealy bugs so you are not alone. The fungal oil did not work because mealy bugs are not affected by fungus treatments. The best way to eradicate these insects is to swab them first with rubbing alcohol which melts away the white waxy coat they wear. Follow up by spraying Bonide All Seasons Oil or Bonide Eight All Insect spray. Make sure that you have watered them in advance of any treatment.


Dear Garden Guru,

I have a new meyer lemon brought home in the past year. The leaves have recovered from initial yellowing, but are now being chewed on by something. I haven't seen the culprits, but a couple of leaves have been chewed almost in half. What would be a good approach for thwarting the unidentified culprits? (This is in the Excelsior area of San Francisco)

Laura in San Francisco

Hi Laura,

The main culprits are usually either caterpillars or slugs and snails (and sometimes earwigs). With slugs or snails you will generally see holes forming in the middle of the leaves. Plus there is usually a slimy trail left behind on the leaves too. All of our Sloat locations carry slug and snail controls that would help if this is the case.

Caterpillars will eat the leaves from the outside in. The outer edges of the leaves look like they have bite marks on them. They can certainly eat a fair amount of leaves on a citrus tree. If this is what is happening, there is really only one active ingredient that works against caterpillars, called Bacillus thuringiensis (Bt). You can also find this at any of our stores, made by Safer Brand.

Earwigs can do damage similar to that of caterpillars, but caterpillars are the more frequent attacker. If you find that the caterpillar killer is not solving your problem, then our Greenlight Slug and Snail bait also works on earwigs and could potentially handle multiple problems for you at the same time.

Additionally, spying on your tree late at night with a flashlight might help you discover what it is that is feeding of your plant.

I hope this helps. As always feel free to visit any of our garden centers for more expert advice.

Curious if we have your favorite plant or product in stock? Call one of our locations directly and we'll be happy to check.