Ask the Garden Guru

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

Waterwise Privacy Screens

Dear Garden Guru,

I am looking for a waterwise, evergreen shrub that will grow 10ft tall to provide a privacy screen. Any suggestions?

Carin in Novato

Hi Carin,

Hello! Good candidates for your purpose are:

  • Podocarpus (all species and varieties: gracillior, macrophyllus, Icee Blue)
  • Dodonaea ‘Atropurpurea’, the Hopseed
  • Rhamnus alaternus and Rhamnus John Edwards
  • Pittosporum tenuifolium


Fungus gnats on my ficus

Dear Garden Guru,

I have some little black flies in my apartment and today noticed there were more of them gathering around my ficus plant...the soil in the pot. Without using chemicals, can you tell me how to rid my home of this pestilence! Thanks.

Nina in San Francisco

Hi Nina,

Those little buzzing pests are fungus gnats. They become a problem when houseplants (or greenhouse plants) are over-watered or when the soil stays constantly moist. Overly moist soil is more relevant to the gnats indoors because the temperatures stay warm. The adult gnats lay eggs in the soil. The larvae hatch and begin to feed on the decaying organic matter of the soil (and can sometimes harm roots if their numbers are great). They pupate and then emerge as the annoying gnats to start the cycle again.
The cycle can be broken if the soil is kept drier, allowing more time between watering. Repotting a plant into fresh soil will also help. There is also a product called Gnat Exterminator. They are beneficial nematodes (microscopic soil dwelling “worms”) that prey on the gnat larvae. They are applied as a spray to the infected foliage. Sloat also carries a miniature sticky trap, called Gnat Sticks that can be placed in the pot to trap the adult gnats.

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:


Tomato plant troubleshooting

Dear Garden Guru,

My tomato plants always look beautiful when I get them in the ground. I water and fertilize and then right after the plants flower they turn yellow and spindly and they don't fruit very well. What am I doing wrong?

Liz in San Bruno

Hi Liz,

Yellow and spindly tomatoes don’t fruit that well do they? Believe it or
not, I suspect that you are loving your plants too much. Over watering
tomatoes will wash away all the nutrients you so lovingly applied, it also
reduces needed oxygen in root zone and makes the plant susceptible to
disease. Your plants should be deep watered 2 to 3 times a week. If the
plant is seen wilting in the middle of the day, ignore it. Tomatoes will
close their stomas in the heat of the day to prevent water loss by
transpiration. They will perk right back up by late afternoon. If the plants
look droopy in the morning, they need water. Too shady a location will also
cause plants to be spindly but you usually see that effect immediately. If
the leaves are showing some signs of browning, your plants may have
Verticillium or Fusarium wilt. These are soil borne pathogens and there is
no chemical control available. Warm and humid conditions will hasten the
onset of wilt. It is highly recommended that you plant tomatoes labeled
with “VF” (Verticillium/Fusarium) on the label as these are resistant
varieties. Should there be an “N”, that means resistant to root knot
nematodes. Hope this helps for this year’s crop!

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.

Fruit Tree Planting in Winter

Dear Garden Guru,

I would like to plant fruit trees this winter but I live very close to the ocean, with lots of summer fog. Which fruit trees would you recommend for my microclimate?

Melissa in San Francisco

Hi Melissa,

For your foggy, coastal conditions consider Santa Rosa plum, Meyer Lemon, Persimmon, Asian Pear 21st Century, and Apricot.

For something more exotic, the Pineapple guava, Feijoa sellowiana, will work. You could also consider Blueberries!  Many of these will be available in January or by special order later in the season.

What do I grow in my container garden during the winter months?

Dear Garden Guru,

I'm from the midwest, where the winter snow prevents people from growing year round. Now that I'm in San Francisco, I have no idea what to grow in my container garden in the winter months. Any suggestions for what do on my patio from October-March would be most helpful to this midwest gardener!

Courtney in San Francisco

Hi Courtney,

You are in for a treat because the fall/early spring gardens are fun.  Annuals that are available in September are stock, pansy and viola, snapdragons, paludosum daisy, and Iceland poppy.  The snapdragons and poppy will look there best in early spring  but are best established in the fall.  The others will give you color even in the winter months.  Arriving in October are primrose, ornamental cabbage and kale, and Cyclamen.

If you want to grow some edibles,  lettuces, peas, broccoli, kale, Brussels’s sprouts and chard are available as starts, or you can start from seed.  Best from seed are onions, carrots, beets and other root vegetables.  Herbs such as parsley, thyme, sage and rosemary can be planted.  Of course, our full selection of spring flowering bulbs are available in September.  Bulbs over planted with violas work very nicely in pots.  October is also the best time to plant sweet peas, foxglove, and California poppy.  There are also fall garden mums!   There’s a reason this is such a popular state.

Do bulbs need to be refrigerated?

Dear Garden Guru,

I have dozens of bulbs for fall planting. I've learned I have to refrigerate the crocus, hyacinth and tulip bulbs, but I'm getting mixed messages on refrigerating daffodils in Northern California. Do daffodil bulbs need to be refrigerated in this area? Anything else I should or shouldn't refrigerate? (I know about not keeping fruits in the fridge with the bulbs.) Thanks!

Susannah in Kentfield

Hi Susannah,

You do not need to refrigerate Daffodils or Narcissus. Some people keep Paperwhite Narcissus in the refrigerator to “stall” sprouting so they can force the bulbs over a longer period of time. This is probably where you are getting a mixed message. While not necessary, some people like to chill their Freesias – it seems to make the stems sturdier.

What is the best time to plant bulbs?

Dear Garden Guru,

When is the best time to plant tulip bulbs?

Pat in San Francisco

Hi Pat,

Dear Pat,

Our selection of tulip bulbs is available in the fall. It’s best to have all bulbs in the ground by Thanksgiving Day. Bulbs are available at most Sloat Garden Center locations.

Read more about planting bulbs here:

Growing sweet peas

Dear Garden Guru,

When is the best time to plant Sweet Pea starts? When are they for sale? Thanks!

Lisa in Novato

Hi Lisa,

Alas, the best time to start sweet peas in your climate is in October. Planted in the fall, they develop strong root systems and then take off in the spring. Both seeds and starts are available. The second best time is in February. Our stores will have packs of tall-growing sweet peas available in a variety of colors.

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