Ask the Garden Guru

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Thank you!


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.

Lawn Care – Native sedge lawns

Dear Garden Guru,

We would like to grow a lawn of native sedge grass that won't need much watering. What is the best type of sedge for the kind of lawn that kids can play on? How do we approach the planting process? Is it better to use seed or plugs? Obviously a sod would be a quick planting process, but I don't think that is an option. Or is it? Cheers.

Jennie in San Francisco

Hi Jennie,

Native sedge lawns really are a great solution to the common lawn but you are right, they can’t be planted by seed or sod. They are planted by plugs on 10″-12″ centers on the diagonal. Sloat does not have a vendor that supplies native grass plugs but there are 2 local reforestation nurseries that sell to the public. They are Bay natives in San Francisco ( and Elkhorn nursery ( John Greenlee , the grass guru, also sells plugs on on his website They are not inexpensive (about $2.00 a piece). John Greenlee also has a new book out about how to plant a native meadow lawn.

The variety best suited for our area is California meadow sedge, Carex pansa. In general preparation for planting plugs is similar to that for seed or sod. Remove weeds and old lawn completely, add organic amendment such as Forest Mulch Plus (found at your local Sloat store) and roto-till, install irrigation (now is the time to do it right), apply a pre-plant fertilizer such as Sure Start, rake smooth. I hope this helps you in your quest. Good Luck!

Plant suggestions for an outdoor terrace

Dear Garden Guru,

I'm moving to an apartment with a huge terrace and excellent light: morning noon and early afternoon. I don't want to get one plant at a time and assort a junk yard collection of plants. My question is, what kind of large containers could I get that look modern and what kind of plants should I buy? This is by Mission Creek in Mission Bay, not far from the ball park. I'm leaning toward natives because while I might water them diligently, I can't have an automatic system and want to ensure they outlive occasional neglect. Lavender? What kind of soil?

Bill in San Francisco

Hi Bill,

In terms of modern containers we do carry a lovely line of Fiberstone pots that are lightweight and modern looking. And, of course, we have tons of styles of pottery and redwood containers to choose from as well.

I think going Native is a great idea. There are plenty of low-water options that will do well in containers. Some examples are: Aquilegia (columbine), Artemisia, Ceanothus (wild lilac), Erigeron, Heuchera and Penstemon. This is but a short list. We can personally show you a larger variety at any of our San Francisco locations.

Lavender is not a native, but does quite well in containers and does not need a lot of water either. You may also want to consider a cactus/succulent garden. You can get many different colors and textures from succulents, and they certainly have low water requirements.

Euphorbias and Phormiums are two more excellent choices you may want to check out.

With any and all of these you will want to use a Potting Soil. At Sloat stores we differentiate between Potting Soil and Planting Mix by whether or not the soil is going into a container (potting soil) or if it is going into the ground (planting mix). In your case the drainage needed in container planting is made possible by using potting soil. Although you can also consider a cactus/succulent specific soil too if you go that route.

I hope this helps get you started. And again, please do visit any of our locations to see some of these plants in person and get additional direction from our educated staff.

Treating "doggie" areas in the yard

Dear Garden Guru,

My son, who temporarily lives with us, owns a female dog who urinates and defecates on every living thing in the back yard. Now I have completely dead areas, probably due to the excess nitrogen. What can I use to 1) keep her out of the areas; 2) what products, if, any, would treat the clay soil and bring it back to "normal"...

Cheryl in San Francisco

Hi Cheryl,

Thanks for your question. You are certainly not the only one to have to deal with these issues. There are a couple of ways to approach “protecting” your back yard. One is with physical measures like 1 to 3 ft high border fencing, which would keep the dog out of any areas that you choose to enclose. Stakes and netting can also accomplish this (although that doesn’t look quite as nice and is a bit more temporary).

We carry a great product called Dog & Cat Repellent made by Liquid Fence. It can be sprayed around areas that you would like to protect, and can even be sprayed directly on to plants. This is an excellent solution for protecting SOME areas. It will not provide complete coverage because if the entire yard smells bad to the dog and she really has to “go” then she’ll still do her business somewhere in the yard. However, if you have one area in the yard that you want to steer the dog into (perhaps one sacrificial area) then you can spray all other areas, hoping to direct the dog into that one zone you are aiming for where you have not used the spray.

As for helping the soil, if it’s really only been a short amount of time that the dog has been around, I think you’ll be fine without doing too much to “repair” the soil. As long as you are still watering regularly, it would take a while for any real damage to occur. I would, however, replenish your soil with Planting Mix once the dog moves out, or perhaps once a month while the dog is living with you. Just this little added “fresh” soil will help keep plenty of nutrients alive and keep your plants happy.

I hope this helps. And, as always, feel free to ask more questions at any of our locations, particularly if you see problems developing.

Amending your soil

Dear Garden Guru,

What are the first steps in trying to assess the amendments that need to be added to make soil healthy?

Alyssa in Pacifica

Hi Alyssa,

The first thing you will want to do is obtain a soil test kit. We carry single test to multiple test kits. They are very easy to use. Basically you put a sample of your soil in vial, add water and one of the test reagents. It changes color and you then look at a chart to read your result. The test assays for pH, Nitrogen content, Phosphorous and Potassium. Plants grow best in a pH of 5 to 6. If your soil is say a pH of 8 you will want to add Aluminum Sulfate or Soil Sulpher plus an organic amendment such as Planting Mix or Forest Mulch Plus. If your pH is 3, you would add Agricultural Lime. If you are lacking any of the nutrients, the test has recommendations for you to follow. If your soil tends to be clay-like, we recommend Gypsum and the addition of Organic matter. If your soil is sandy, we recommend the addition of Planting Mix.

Plants for shady gardens

Dear Garden Guru,

What plants are best for shade?

Carol in San Francisco

Hi Carol,

Very few plants grow in full (never see the light of day) shade but the following list will grow in part to heavy shade depending on where you live.

  • Abutilon
  • Alchemilla mollis
  • Astilbe
  • Aucuba japonica
  • Ajuga reptans
  • Campanula portenschlagiana
  • Coleus
  • Heuchera
  • Hydrangeas
  • Hypericum
  • Japanese Maple
  • Japanese Painted Fern
  • Lamium
  • Lysimachia
  • Mimulus
  • Rehmannia elata
  • Sollya heterophylla

I would recommend that you not plant directly under a lemon tree unless the tree is quite large.  A young or middle-aged citrus can suffer from to frequent watering.  If you are planting around the perimeter or the edge of a pot if that is how the lemon is planted, I might suggest:

  • Thyme
  • Rudbeckia
  • short sunflowers
  • coreopsis
  • Scented geraniums
  • Edible salvia
  • Lavender

Benefits of Mulching

Dear Garden Guru,

My co-worker suggested that I apply some mulch to my yard. What are the benefits of mulching? Also, when is the best time to apply the mulch?

Daniel in San Francisco

Hi Daniel,

Your co-worker knows what he/she is talking about. Mulching has many benefits in our Mediterranean climate. First and foremost, mulching decreases moisture loss from evaporation, thus allowing for less frequent watering, conserving our most precious resource. Secondly, mulching will inhibited most weed growth (barring very aggressive weeds like ivy, Bermuda grass and other nuisances) limiting the need for herbicides and saving your time and labor (our second and third most precious resources).  As a long-term benefit, as mulch decomposes, it adds organic matter to the soil helping to loosen heavy soils and keep the soil healthy.

The most popular mulches we sell are Forest Mulch Plus (containing 15% chicken manure to add nitrogen to the soil) and Micro Bark (a true top-dressing that can last for several years with minimum replenishing). Other choices are Shredded Redwood and Cedar barks (for slopes or if you prefer a “fluffier” look) and Patio Bark (sometimes referred to as “Tanbark” which comes in fine, medium and coarse grades).  Hope this helps.

Gardening with children

Dear Garden Guru,

At our preschool we do all of our gardening in large planter boxes. We like to do our gardening projects from September to June so the children can see the full cycle of the plants. Can you suggest plants that would be good for this type of garden activity and age group?

Bobbi in Larkspur

Hi Bobbi,

For the Fall consider peas, cabbage, broccoli, cauliflower, spinach, and any lettuces and leaf crops.  Pansies and violas will add great color and the flowers are edible.  Iceland poppies, stock and primrose will flower through the winter.

For the spring consider California poppies, bulbs such as daffodils, freesia and tulips (to be planted in the fall) as well as beans, more peas and all leaf crops.

Starting out as a new Bay Area gardener

Dear Garden Guru,

I recently moved to San Francisco and into a place with a garden. I have never thought of myself as a gardener, but really want to start. I was wonder what plants you would suggest for a garden newbie like myself. I would prefer flowering plants so I can enjoy the fruits of my labor, as well as plants that are fairly hardy and easy to care for! Thanks!!!

Katie in San Francisco

Hi Katie,

Welcome to the neighborhood! First, San Francisco has very sandy soil so anything you plant will benefit from adding amendment to help the soil retain water. We recommend Forest Mulch Plus or Planting Mix. If you enjoy flowers, look to perennials such as Salvia greggii, Penstemon, Abutilon and Euphorbia. Larger plants like Echium, Marguerite Daisy and Rosemary will add stature to your planting. Annuals live only 1 season but pack a powerful punch of color and often reseed. Try Nasturtium, Alyssum, Lobelia and Nicotiana. There is a good article on gardening in the city in our July/August 2006 Notebook that you can view on our website. It might be fun to rototill or dig a small space in the garden and sow a Bay Area wildflower mix. I also encourage you to visit any of the city stores and ask our staff what their favorite picks are!

Overly Damp Areas

Dear Garden Guru,

We have an area in our yard that is quite wet--especially during the rainy season. It is in partial sun, but mostly on the shady side. Do you have any suggestions for plants/trees/shrubs that would like these very wet conditions? Any plants that would help soak up some of the water? Thanks very much!

Amelia in San Francisco

Hi Amelia,

Here are some suggestions for overly damp boggy areas. Please keep in mind that any soil you plant in should be heavily amended with a soil additive such as Sloat Planting Mix to keep as much air around the roots as possible. Also keep in mind that boggy areas are some of the least forgiving in the garden and the suggested plants may not work in your particular area. Severe yellowing, stunted growth and/or drooping will be early indicators of suffering plants.

Perennials/Bulbs: Calla Lily (Zantedeschia aethiopica), Elephant Ears (Alocasia and Calocasia), Lobelia cardinalis, Forget-Me-Not (Myosotis), Spiderwort (Tradescantia), Hostas, Chameleon Plant (Houttuynia), Horsetail (Equisetum)

Ferns: Matteuccia, Athyrium, Woodwardia fimbriata
Grasses: Scirpus, Chondropetalum, Cyperus
Shrubs: Birch (Betula), Willow ( Salix)), Gaultheria, Huckleberry (Vaccinum
ovatum), Blueberry, California wax Myrtle (Myrica californica)

I hope this proves helpful and thanks for gardening with us.

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