Ask the Garden Guru

Dealing with leaf miners in chard

Dear Garden Guru,

I just noticed that I was getting weird coloring on some of my swiss chard and spinach leaves. It looks like something is burrowing in the leaves. I did a little research and narrowed it down to leafminers. What can I do to get rid of these pests?

Maria in San Francisco

Hi Maria,

Those are indeed leaf miners. The adults are small black flies that emerge from small brown pupae in either your soil or the neighbors. They are active from April to September. The adult flies lay white eggs on the undersides of chard, spinach, and beet leaves. The young burrow between the leaf surfaces, and once there, are impervious to sprays.
The goal is to keep them from maturing. Check leaves often for signs of eggs and destroy them. Remove portions of leaves that are infected by leaf miner and dispose of them (don’t compost them). You can protect plants from the flies by covering them with floating row covers (We sell Harvest Guard). You can also spray your plants once a week with the organic Spinosad. It works by killing new egg hatches.

What is eating my container plants?

Dear Garden Guru,

Something is eating our very lovely bay laurel container plant - only the new growth leaves at the top. Same goes for the spearmint nearby. Do you know what this is and is there anything to do?

RR in San Francisco

Hi RR,

Chewing insects are not known for bothering Bay Laurel. I suspect it is probably snails and slugs bothering both the aromatic herbs. You can apply Sluggo or Sluggo Plus (this one includes Spinosad that gets chewing insects, just in case) to the containers. The baits are non toxic to pets, birds, amphibians, etc. I would check the laurel for small baby snails hiding under the leaves or at the base of the mint.
Thanks for choosing to garden with us.

Gnat troubles on indoor plants

Dear Garden Guru,

I have been getting gnats in many inside plants. I had them this winter and I changed soil and cleaned plants time and again and thought I finally was Ok, but they keep returning. I have had indoor plants for 40 yrs and never a problem till this winter. Please help me thanks.

Joan in San Rafael

Hi Joan,

The soil or fungus gnats become a problem when the soil is kept too moist and not allowed to dry out much between waterings. The larvae of the gnats feed on the small fungi that are decomposing the organic portion of the potting soil, primarily peat moss and mushroom compost. Too many larvae in a pot and they can begin to feed on the plant roots as well. To control them, keep your plants on the dry side. You have already gone through the changing of the soil. Sloat carries beneficial nematodes (aptly named fungus gnat destroyers) that can be applied to the problematic containers. The nematodes eat the larvae thus breaking the cycle. Small yellow sticky traps called Gnat Stix can be attached to the rims of the pots to catch the annoying adults.

Insect bites after working in the garden

Dear Garden Guru,

I am getting a lot of bites from invisible insects when I work in my garden. I suspect mites. Is there any way to get rid of them (an organic solution preferred if possible)? Thanks.

Jon in Mill Valley

Hi Jon,

I suspect your invisible biters may be juvenile mites known as chiggers. If you have tall weeds or grass keep them cut down. Blackberry thickets and creek sides are also well known harbors for chiggers. The juvenile mites hatch and mature beneath the soil level so applying beneficial nematodes may help eradicate them. Other hard to see bugs are small midges that bite very much like mosquitoes. Apply mosquito dunks to ponds and water features such as fountains and bird baths. Use an insect repellent on your garden clothing that contains .5% Permethrin. Yes, this is a synthetic chemical that acts like pyrethrum but it is certainly safer for you than DEET and you are spraying your clothing, not the environment.

Dog pee is killing plants

Dear Garden Guru,

Help! My garden is dying! My container plants, lavender, succulents and potato vine are all dying rather quickly. (Only my coleus are surviving) I have tried plant food, different watering techniques, sluggo and more but it just look dead. I live in the Mission, get areas of good sun and put plants in their proper "climate". We do have three dogs in the building that use the yard as their bathroom though--much to my chagrin. Can pet pee and poop toxify the environment? Any help is appreciated.

Uda in San Francisco

Hi Uda,

I am afraid that dog pee and to a lesser degree, excrement can harm plants. This is especially true in warmer or hot weather. Dog pee contains strong ureic acids that will quickly burn foliage or roots if not washed away quickly. Male dogs have a tendency to aim at containers and hit all the corners. Plants that have been marked are more subject to burn in that the other dogs will pee over the first dog to mask the scent so the plant receives a double or even triple dose. You may want to use a repellent such as Repel, Shotgun or Bonide Dog and Cat to keep the dogs away from your plants.

Fighting Bermuda grass

Dear Garden Guru,

How do I kill bermuda grass - without using pestisides. Desperately seeking organic solution.

Victoria in San Francisco

Hi Victoria,

Fighting Bermuda grass is a struggle, whether by organic means or no. There is a spray we carry called Bonide Lightning Fast. It is basically a strong soap solution. This will burn out top growth very quickly, especially on really hot days. 10% to 20% solutions of Vinegar will also work. If the patch is small, consider boiling water which will kill the roots too. The problem with Bermuda is the stolon root system which readily breaks. One little root piece left and it regrows. The small seeds it forms are another issue.

After you have burned back the top, rent a sod cutter. Set the sod cutter on the lowest setting to strip as much of the stolon mass away as possible. This is the expensive part of the venture as the removal of dirt and debris can be costly. After removal, utilize the lasagna method of mulching the area: first cardboard/newspaper, mulch, more newspaper/cardboard, and lastly, more mulch. Please know that you probably will not have found all the stolons and they will happily invade the new space. Hand pull these new patches as they arrive. Do not let seed heads form!

Persistence will pay off as long as you realize that you will never completely get rid of it. Cohabitation is a more likely result.

How to keep the neighbor's cats away

Dear Garden Guru,

Recently a neighbor's cat has taken to coming into our garden and defecating in various areas - digging up the dirt in potted freesia bulbs that had finished blooming and digging up the baby tears ground cover. The garden was a sanctuary but is now becoming one big sandbox for this cat and it's pretty disgusting to have to pick up after it. It's not only smelly but unsanitary as well. Is there any way to keep the cat away? Please help.

Mary in San Francisco

Hi Mary,

The Bonide Dog and Cat repellent can be sprayed along the perimeters of the garden as well as in the areas that are being disturbed. Cats also dislike citrus oil. Orange peels that have been chopped fine in a food processor can be sprinkled in pots. Bamboo skewers, cut into 3″-4″ lengths, and spaced 3″ apart can be in inserted in pots and planting areas also to prevent digging.

Stop cats from using my vegetable garden as a litter box

Dear Garden Guru,

How can I discourage neighborhood cats from using my vegetable garden as a litter box? How can I keep them out?

Emily in San Francisco

Hi Emily,

Sloat carries a couple products that can help you. The first is Critter Ridder. It is a granulated, pepper based repellant that is safe too use around your vegetables. You can directly sprinkle the product around your garden. The second is Liquid Fence Dog and Cat repellent. It has a much stronger smell and is designed to be sprayed around the perimeter of the yard or garden boundary. Once dry, you will not notice the smell.

Another trick that can be used is to sprinkle orange peels where the cats are going. They dislike the smell of orange oil. It is possible that the product Orange Guard will work as well but it’s not listed on the label for this purpose.

Getting oxalis out of the garden

Dear Garden Guru,

I have very abundant oxalis in my garden beds. We just moved to this flat, our neighbors have just been spraying weed killer every now and again to keep it at bay. They haven't planted the beds and stopped the weed killer when we told them we wanted to plant the beds. I want to plant vegetables and flowers including, bulbs, sweet peas along the fence and abutilon, clematis etc. Any thoughts? I have two sections of about 15 by 5 ft beds.

Nalani in San Francisco

Hi Nalani,

You should attempt to dig as much of the Oxalis out as possible. Mature plants have many small bulblets at the base. Sifting the soil after you have dug what you can will help capture any loose bulblets. Cover your beds with the lasagna method of mulching. First wet newspaper, then cardboard, then compost or forest mulch, then more newspaper, planting mix, cardboard, then compost. You can plant directly into your lasagna layers. Any Oxalis trying to resprout will be depressed by the mulch layers.

Keeping a fat happy raccoon out of the garden

Dear Garden Guru,

What are your suggestions for keeping a fat happy raccoon out of the garden -- my garden is small and totally fenced, but that is not a deterrent.

Sheila in San Francisco

Hi Sheila,

If this critter is a regular visitor, it is possible that he/she lives on the property. Look about for openings under stairs, access under the house or into the garage. Make sure all these openings are screened. Do not leave garbage cans and pet food outside. Harvest ripe fruit from trees. If it is a lawn area or bed that is being dug up, use one of the granular repellents such as Critter Ridder or Repels All in the areas being disturbed. If there is standing water such as a birdbath that can be used for drinking or “hand washing”, empty it.

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