Gardening
for Your Watershed – May
2004
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Topics in this issue:
* Fertilizers: Go Organic or Not?
* Pest of the Month: Tent Caterpillars
* Mini-Compost Classes
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Fertilizers: Go Organic or Not?
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Your plants don’t really care if their nutrients come from an organically-derived fertilizer or one that’s synthetically derived. All they know is that they need nitrogen, phosphorus, and potassium, along with other minerals--chemicals are simply chemicals to them, no matter the original source.
However, what does matter is the timing. If too many nutrients are released into the soil, plants can’t take them all up. They end up being leached by water (either from rainfall or irrigation) below the root zone, so that plants can no longer use them, and may enter ground water. Alternatively, water may wash excess nutrients away along the surface of the ground, into streams and lakes. Not only is this a waste of fertilizer (and your money), it can contaminate your ground water or your local stream or lake. Nitrate contamination can cause “blue baby” syndrome; phosphorus pollution of lakes and streams can be harmful to fish and other aquatic life because it can trigger algal blooms.
Organic fertilizers certainly aren’t bad, but they may not always be the most appropriate source of nutrients for your plant. Organic fertilizers are by nature slow-release, which is good if you want a gradual (though unpredictable) release of nutrients to your plants, but not as beneficial if your plants need an immediate boost. Many organic fertilizers are low in nitrogen, which is often the nutrient most needed by a plant.
On most bags of fertilizer, you’ll see three numbers. This is called the N-P-K ratio (after the atomic symbols for nitrogen, phosphorus, and potassium). If a bag says 5-10-10, that means that it’s 5% nitrogen, 10% phosphorus, and 10% potassium. A 10-pound bag of 5-10-10 fertilizer will have 0.5 pound of nitrogen (5% of 10 pounds is a half-pound), 1 pound of phosphorus, and 1 pound of potassium. Sometimes a bulk organic fertilizer will not have an N-P-K ratio listed. For some N-P-K ratios of common organic fertilizers, see:
Garden Hints: What are Nutrient Values of Organic Fertilizers?
Ultimately, when choosing a fertilizer, choose one that’s right for your plants. Vegetables will have different nutrient needs from your lawn, and your perennials may need yet another formulation. And keep in mind the following general tips for any kind of fertilizer:
- Don’t apply
more than you need. More fertilizer is not better--it can actually
lead to weaker plants that are more prone to diseases. If
your fertilizer includes instructions on application rates, follow
them scrupulously.
- Fertilize when
your plants are growing. For perennials and vegetables, this is
the spring and early summer. For grass, this is early spring
and the fall. And if you’re fertilizing something like vegetable
seedlings, remember that a small plant doesn’t have much of
a root zone. Putting fertilizer down outside of its root zone just
means that
water will leach the nutrients away before the plant has a chance
to use it. So only put a little bit of fertilizer in with your seed
(or
seedling), and as the plant grows, sidedress it with fertilizer as
necessary.
- Split your applications, if appropriate. For example, if you want to put four pounds of nitrogen on your 1,000 square-foot lawn over a year, and you want to do one application in the spring and one in the fall, you’ll need to put just two pounds of nitrogen each time. Don’t put the full four-pound application on each time! A 16-0-8 fertilizer in a 50-pound bag contains eight pounds of nitrogen, so to apply two pounds of nitrogen, you would put 12.5 pounds of fertilizer on your lawn (2 is 25% of 8, so you would use 25% of the 50-pound bag, or 12.5 pounds). If you had 500 square feet of lawn, and wanted to apply the same rate of nitrogen, you would cut the amount in half (500 is half of 1,000) to 6.25 pounds of fertilizer per application.
Confused? Call a WSU Master Gardener for help at 676-6736 (9 a.m.-noon, Monday through Friday). Or for more details on fertilizing, see these publications:
Time to Think about Garden Fertilizers
Gardening and Water Quality: Using Nitrogen Fertilizers Wisely
Gardening and Water Quality: Understanding Nitrogen Fertilizers
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Pest of the Month: Tent Caterpillars
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In spring, some of your decidious trees might look like they have wads
of cobwebs bunched up in their foliage. These clumps are actually
the silky nests of western tent caterpillars (Malacosoma californicum
pluviale),
who like to band together for protection as they nibble away at your
trees’ tender new leaves. Healthy, mature trees can bounce back
from loss of leaves without any treatment, but a single tent’s
worth of caterpillars may take out as much as 20% of a young tree’s
foliage, substantially weakening the tree.
The western tent caterpillar has a dark body with orange, white, and blue markings. As they mature, the caterpillars begin to become more solitary, feeding by themselves or in smaller groups. In June, the mature larvae wander away from the host tree and pupate by forming a white, puffy cocoon. After about ten days, hairy, reddish-brown moths emerge from the cocoon. Shortly after emerging, the adults mate, and the females lay eggs in frothy batches of 100 to 350 on host tree branches. The eggs will stay glued on the tree until the larvae hatch the following spring.
Decision making:
- NEVER use fire
as a control method for tent caterpillars (or any other pest problem).
Burning the tents can result in more damage to the tree.
Additionally, this practice may result in personal injury and
property damage. Last year, a Poulsbo teenager was seriously burned
while
using gasoline to rid a tree of tent caterpillars.
- A simple solution
is to prune the tented branch. It is best to do this at night or
early morning, when the caterpillars are congregated
in the
tent. Dispose of the branch by placing into a yard bag or trash
can so the larvae cannot escape and continue feeding.
- In the fall
and winter, egg masses are
easily seen on small trees. Simply peel off from the bark and
put them in the trash.
- Chemical management of tent caterpillars is an extreme response to a serious tent caterpillar problem. Most of the time, mechanical controls will take care of the problem. Visit WSU Hortsense (http://pep.wsu.edu/hortsense) for current recommendations.
For more information
about tent caterpillars, visit:
http://whatcom.wsu.edu/ag/homehort/pest/tent_caterpillar_update.htm
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Composting Classes
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Compost is a terrific soil amendment--it loosens up clay soils, helps sandy soils retain water, and adds organic matter and beneficial microbes. Composting is a great way to break down your yard and kitchen waste into a useful and versatile garden product.
WSU Master Composters are teaching several how-to-compost classes in early May at Hovander Homestead Park in Ferndale, at the compost demonstration site near the farmhouse. The dates and times of the May classes are:
Thu 5/6, 5 p.m.
Sat 5/8, 1 p.m.
Sat 5/15, 9 a.m.
There will also be classes in every Thursday in June at 5 p.m., and every Saturday in July at 9 a.m. (except for the weekend of July 4).
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This newsletter
is produced by Whatcom County Extension. To subscribe or unsubscribe,
or to make comments and suggestions, please contact Scarlet
Tang or
360/676-6736.
