Ask the Garden Guru

The Garden Guru  is on vacation. Please check back October 18th.

Thank you!


When should I start planting?

Dear Garden Guru,

Recently I moved from San Bruno to San Carlos. When is the ideal time to plant my garden seedlings? I wonder if it too early to start my garden (particularly tomatoes)?

Mara in San Carlos

Hi Mara,

You can start your gardening projects right now. This would include planting your seedling vegetables (peas, greens, strawberries, cabbages, kales, beets, carrots, onions, spinach), as well as the tomatoes, beans and squashes and basil. All Sloat Garden Centers now have the most varied vegetable selection of the season. As you plant during this cool spring weather, please keep in mind that tomatoes need consistent warmth. If you want to plant tomatoes now, you will need to protect them from cold nights.

Growing salad greens

Dear Garden Guru,

I'd like to know the best way to grow salad greens throughout the summer. Can I plant them in succession so that I'll have 4 months of salad? Also, I live in a foggy pocket of the east bay - does that make a difference?

Beth in El Cerrito

Hi Beth,

The easiest way to get your summer greens going is to start with pre started cell or jumbo packs. You can always supplement with a sowing of seed.

Should you opt for seeding only, be sure that you do not bury the seeds too
deeply. The best results with lettuces and greens is to prepare the bed (be
sure to mix in Loam Builder and Agricultural lime) so the soil is nice and crumbly. Sprinkle the seeds on top of the soil and then water. The seeds will settle into the soil at the right depth. Carrots and Lettuces need UV light to germinate! You do not need to pull up whole heads, it is better to cut the plants off about an inch above the soil. The greens will quickly regrow. Feed with a liquid fertilizer such as Maxsea All Purpose after cutting. Should you want to pull up whole heads or the plants begin to slow down coming back, you can resow or plant every 3-4 weeks to keep a fresh crop coming. The fact that you live in a cool, foggy location is actually a blessing for growing greens. They do not like it hot. We actually recommend planting in part shade in our hotter areas.

Powdery mildew on zucchini plants

Dear Garden Guru,

Last year I had a lot of trouble with powdery mildew on my zucchini plants. I read somewhere that I should treat the soil with a copper spray before I plant zucchini this year. What do you recommend?

Pat in San Franciscos

Hi Pat,

You could spray the copper spray on the existing soil to kill any over wintering spores but the truth of the matter is that the spores are already blowing about anyway. First, make sure to prepare the soil well so that it will hold adequate moisture between watering. Stressed plants are more susceptible to disease. We like Loam Builder for the ground and Organic Potting soil for containers. The addition of Agricultural Lime will provide necessary calcium which not only inhibits blossom end rot, but also helps with disease resistance. Choose varieties that are hardy such as Burpee Hybrid or Black Beauty. Avoid getting the leaves wet and water only in the mornings. It is normal for zucchini to have silvery white patterns on the leaves. Don’t confuse them with powdery mildew.

There has been recent research that shows zucchini were protected from powdery mildew by spraying them with a water/milk solution. That’s right, milk. Spray the plants in the morning every other week with a solution 1 part milk to 9 parts water. Resist the temptation to increase the milk. Not only did this spray act like a foliar food, but infections were controlled by the spores contact with calcium in the milk.

Growing GMO-Free seeds

Dear Garden Guru,

This is my first year to have a vegetable garden. I'm looking around to purchase good seeds that have not been genetically altered and I'm looking for heirloom varieties. Do you carry these types of seeds or can you give me some advice?

Julie in Mill Valley

Hi Julie,

We do indeed carry these seeds. We carry an all-organic line of Botanical Interest seeds that contain no GMOs. 142 varieties of vegetables (many heirlooms) and flowers. You can read about them in our current March/April Gardener’s Notebook. All of the Sloat stores carry them.

What kind of apple tree to plant?

Dear Garden Guru,

I am interested in planting an apple tree in Bernal Heights. I have heard Anna's and Dorsett Golden do well. I have also heard that most apple trees need a second tree to pollinate. What do you think of planting grafted trees (two types of apple on one root stock)? Are they strong enough? Do they develop problems later? There are crab apple trees about 100' from my house. Would they be pollinizers? Thank you so much for your help!

Lori in San Francisco

Hi Lori,

There are self pollinating apples that will do well in your neighborhood. They are Yellow Transparent, Fuji, Red Fuji and Golden Delicious. They are also low chill varieties. If you are interested in a tree that has more than one variety, the best form is an espalier. It is sometimes the case that one of the varieties fails on a multi-grafted tree. A single trunk form would look lopsided whereas an espalier would still retain its shape. A new arm could be produced from a side branch of the variety above or below it. Crabapples can indeed help pollinate fruit apples.

Meyer lemons without flowers?

Dear Garden Guru,

I have Meyer Lemon flowers but no lemons. Has been three years now. I feed it and water also. Why no fruit. Second Q. I have two blue berry plants. Four years old. Loads of flowers no berries. HELP

Chase in San Francisco

Hi Chase,

I suspect that you may be keeping the Meyer Lemon and the Blueberries too dry. Plants will shed their flowers and fruits to conserve moisture. Another possibility is that the flowers are not being pollinated. Where are the plants located? Bees are more scarce and if the plants are in hard to reach places or where there is a lot of wind, normal pollinators may not be visiting you.

When to plant edibles?

Dear Garden Guru,

I live in San Francisco in the Fog Belt and am in process of completely re-landscaping my backyard. I have a very large pine tree that, sadly, is terminally ill and am getting it removed. I'd like to plant edible fruits & vegetables in my yard in addition to some other items. My goal is to plant in February and March. Question 1: is it generally acceptable to plant most things in those months? Are there certain plants that should NOT be planted in late winter/spring? Question 2: Since I have to take down a large tree and will have a bare yard to start, what are some nice plants for the area that grow relatively quickly to make the yard look good and provide some privacy? Thanks!

Rula in San Francisco

Hi Rula,

While our climate is moderate enough to plant year-round, plant availability changes throughout the seasons. Most basic plant material is available in March (February is iffy depending on the weather) but many heat loving or cold tender plants don’t become available until April and May. Spring and summer vegetables become available in mid-February, though March and April are the better months to plant. Cold tender plants such as basil, tomatoes, peppers and melons won’t really start growing until the weather warms up and could be damaged or killed by a cold snap or heavy rains. Recommending a broad selection of plant material via email, without knowledge of your garden exposure, soil type or irrigation, is unadvisable. I recommend that you bring that information into one of our stores and pick the brain of one of our qualified Nursery people. Better yet, contact our Design Department (415-388-3754) for a consultation or visit us on the web.

What vegetables can I grow in the shade?

Dear Garden Guru,

I need a good list of edibles that I can grow out in the Richmond (15th and Balboa). I have a big yard, but it gets lots of shade because of buildings and trees from neighboring yards.

Steve in San Francisco

Hi Steve,

Shade is hard on vegetables. They really need at least 6 hours of full sun to do well. Edibles that can tolerate part shade are blueberries, rhubarb, horseradish, lettuce and parsley. If you are able to be at home for the day, observe where the sun hits and for how long it is in your backyard. There may be more sun than you think, especially now that the days are growing longer. One of our staff at the Third Avenue store will be happy to discuss your options.

Help with veggie garden

Dear Garden Guru,

I would like to start a vegetable garden in our back yard. Would you be willing to come to my house to help me do this?

Linda in San Francisco

Hi Linda,

We have a Garden Design Department that would be delighted to help with designing and coaching you with the process (see link here). If you need help installing, we have a referral list of local professionals, that our designer can supply. With the sun out, our designers are booking up quickly, so if you want to go this route, I recommend that you contact them sooner rather than later.

Blueberry bush troubleshooting

Dear Garden Guru,

Back in late March or so I bought both a bluecrop blueberry and another variety (that has no tag) from the Sloat Blvd location. The one that has no tag was loaded with blooms when I got it--some already forming fruit. Just recently the blossoms have stopped forming fruit though. The blossom goes from white to brown and the whole bud shrivels up and falls off. Otherwise the plant seems pretty healthy, although new leaves look a little wrinkled. Not sure if that's normal. The plant is in a large finished ceramic pot on an East facing deck so it gets lots of light. I planted it in acidic azalea soil. Do you have any idea why this might be happening? Thanks .

Michelle in

Hi Michelle,

Blueberry flowers can die before producing fruit if the plants have experienced dryness or they were not pollinated. It is normal for the flower to turn brown before falling off but usually there is a forming berry behind it, mostly appearing as a flattish disc that eventually fills in. Crinkly leaves are an indication that you had aphids at some point sucking on the new leaf buds. An aphid infestation around the flower buds could also have caused them to fall prematurely. Keep your plants well watered and feed monthly with an acid formula fertilizer. The soil you provided is good. I think you should wait and see.

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