Re: [tomato] Wood ashes around tomatoes

Thomas Giannou (
Thu, 6 Jul 2000 10:33:37 -0700

Dear Marguerite,

Tidbits from around the internet about putting wood ashes on your garden

-  Wood ashes, the residue of burned wood, contain potash, a very strong
alkali. The alkali is recovered by leeching the ashes with water.  They
should be used with caution around roses and acid-loving plants because they
will raise the soil pH.

- What's in Wood Ashes?  This free nutrient for your garden contains all the
minerals that were in the wood. Potash, Calcium, some Phosphurus and a lot
of trace minerals. The important micronutrients it contains are copper,
zinc, manganese, iron, sodium, and boron. Sprinkle all over your garden just
like any other fertilizer. Ashes will make the soil more alkaline, so you
may choose not to put them on the areas you will be growing potatoes,
berries and watermelons who like acidic soil.

- Food and Deodorant  Add the ashes to your compost for their nutrients, and
for their odor-absorbing qualities. The natural fermentation of the compost
creates an acid condition so adding ashes helps neutralize the compost pile.
This is turn helps the microorganisms do their work more effectively. Add to
your inside compost during the winter months to keep the odor down.

- Bug Protector  Sprinkle wood ashes around the base of your plants. Offers
protection against root maggots, slugs, borers, cutworms, bean beetles and
cucumber beetles. For aphid and red spider mite control try dusting on
plants using your icing sugar sifter when the plants are still wet with dew.
Some folks claim it helps keep out rabbits as well. Sprinkle again after
heavy rains. make a paste out of the ashes and paint on tree trunks to
control borers. For squash bugs, bean beetles and cucumber beetles if they
really infest, try this recipe. 1 cup wood ashes, 1 cup lime, and 2 gallons
of water. Mix, strain and spray on affected plants.

Wood Ashes as a Garden Fertilizer
         The author is Ed Perry, Farm Advisor, Stanislaus County Cooperative

At one time wood ashes were a chief source of potassium and much used in
farming and horticulture. While not an important fertilizer anymore, wood
ashes have become plentiful around many homes as more people turn to wood
burning stoves and fireplaces for heat. Gardeners with a supply of wood
ashes often want to know if ashes are useful as a fertilizer or soil
amendment. The questions most generally asked are: In general, wood ashes
contain 5 to 7 percent potassium and 1 1/2 to 2 percent phosphorus. They
also contain 25 to 50 percent calcium compounds. Hardwood ashes contain more
potassium than those from softwood. Wood ashes loose much of their nutrient
value if they stand in the rain, because potassium and other water soluble
nutrients leach out with water. Generally, if leached, the less soluble
carbonates remain, leaving the ashes alkaline.

Are Wood Ashes Beneficial? It depends on your soil. Generally, ashes can be
beneficial; they contain potassium, a major plant nutrient plus a number of
minor nutrients.

Can Ashes be Harmful? Yes, if too much is used. Ashes contain chemicals
which are very alkaline with a pH of 10 to 12. They are harmful at high
rates, especially in soils that are already alkaline. Since about 80 to 90
percent of wood ashes are water-soluble mineral matter, high rates can cause
salts to build up in soils resulting in plant injury.

What Minerals Do Wood Ashes Contain? Wood ashes contain all the mineral
elements that were in the wood. Potassium, calcium, and magnesium carbonate
or oxide are present in comparatively large quantities giving the ashes a
strongly alkaline reaction which can neutralize acid soils. However, the
value of wood ashes as a plant food depends mostly on the potassium content.
How Much Should be Applied? An average application is 5 to 10 pounds per 100
square feet scattered on a freshly tilled soil and raked in. For a pre-plant
treatment, it is best to apply ashes 3 or 4 weeks in advance of planting.
They also can be sidedressed around growing plants or used as a mulch. In
order to avoid problems of excess salinity, alkalinity, and plant nutrient
availability you should limit the application of ashes to 5 pounds per 100
square feet of soil per year.

Avoid contact between freshly spread ashes and germinating seeds or new
plant roots by spreading ashes a few inches away from plants. Ashes that
settle on foliage can cause burning. Prevent this by thoroughly rinsing
plants after applying ashes. Because ashes are alkaline, avoid using them
around azaleas, camellias and other acid-loving plants. Wood ashes are very
low in nitrogen and cannot supply your plants' needs for this element. You
will need to follow your normal nitrogen fertilizer schedule when ashes are

Cooperative Extension Division of Agricultural Sciences UNIVERSITY OF

I think what is important to understand is that the residue left after water
leaches through wood ashes is highly alkaline.  If you put a lot of wood
ashes around your tomato plants, you may now have plants that are suffering
from this high alkalinity.  If that is the case, and the material is laying
on the ground around your plants, you might want to scrape the material away
from your plants and flush the whole area with water in an attempt to get it
away from the roots of your tomato plants so they can recover.  You may also
want to get soil from another part of your garden and put it around your
tomato plants before flushing the area with water.  That should help
moderate the pH around your plants.

Do you happen to know what the pH is in your soils not treated with wood
ashes?  If it is around 6.8, that would be fine for growing tomato plants.

Best Regards,
Thomas Giannou
Spokane, WA

----- Original Message -----
From: "Marguerite Ruch" <>
To: "Tomato Digest" <>
Sent: Thursday, July 06, 2000 9:49 AM
Subject: [tomato] Wood ashes around tomatoes

> The tomatoes now have blossoms and a few small tomatoes, and were
> looking great until wood ashes were put on the soil, around them.   Is
> it likely that wood ashes put in the garden around tomatoes, would be
> the cause of them looking droopy, now?   What can be done to remedy the
> situation, if in fact, this is the cause of them suddenly looking
> droopy?
> Thank you.  Marguerite