My Tiny Plot

There’s not much going on in my garden right now so I’ll carry on with my ‘Master Gardener‘ series.

This week on the course we had a lunchtime speaker come in to talk about slugs and snails. Part of the talk was about how to reduce their numbers in the garden but mostly it was about getting to know slugs and snails better. Because the more you know about something, the better your chances of fighting it. So here goes:

There are lots of types of slugs. The larger ones may look mean but in truth it’s the smallest ones that tend to do the most damage.

If you see a leaf with a ragged-edged hole it’s most likely slug damage. If you see a leaf with a smooth-edged hole it’s most likely a caterpillar or vine weevil . Slugs eat with a dragging motion, hence the ragged edges.

Slugs are hermaphrodites. When they mate both slugs become pregnant. A slug can produce 500 eggs per season.

Their eggs are clear and gradually go opaque. The slugs keep the eggs inside them until there is 25 per cent moisture. Then they lay them.

Slugs avoid eating:
Ferns, Ivy, Sweet Woodruff and Foxgloves (among others)

Slugs love eating:
Hostas (but not the blue, quilted kind for some reason)
Lettuce, Daffodils, Lilies, Strawberries and Primroses (among others!)

They live under rocks, mulch and anywhere it’s moist.

They like to eat at night, or when it’s wet.

Defences include:
Barriers like copper strips, coffee grounds, egg shells.
Salt.
Citrus or Melon halves then trap them.
Beer traps.
Lettuce under a board then trap them.
Nematodes watered into the soil.

Repellants include:
Garlic, Cinnamon, Copper

Slug bait is exactly what it says it is, bait! The slugs move towards it so don’t put it all near your plants. Put it between their home and your plants. In other words find out where they live!

Research shows that it’s best to bait every two weeks because slugs do have some form of memory and can remember where you put it.

Slugs can see about six feet, and they can smell about three feet.

Chances are you’re using too much bait. You only need a light sprinkle. Because they are attracted to it they will seek it out.

And remember slug bait is toxic so only use it as a last resort and away from children, pets and ideally birds.

This week at my Master Gardener course we learned about soil nutrients and how they affect the way our plants grow. Nutrients are pretty important to all plant growth, especially vegetables since they are generally annuals. Any plant that lives and dies in one year is going to require a lot of nutrients.

There are 13 nutrients that are essential to plant growth. None of them are optional. All of them are required for plants to grow healthily, they are just required in different amounts.

Nitrogen (N) is the one that most plants need in abundance. If you think about it, most vegetables will need this in spades since they tend to be leafy, fast growing plants. Phosphorus (P) is another nutrient that plants need a lot of, and so is Potassium (K). These are called the ‘Primary Nutrients’. If you have ever bought a box of general purpose fertiliser for your vegetable garden that said NPK on the side, then now you can see why. They are the three biggies when it comes to growing healthy vegetables.

The nutrient table goes on like this:

Primary Nutrients
Nitrogen (N)
Phosphorus (P)
Potassium (K)

Secondary Nutrients
Sulfur (S)
Calcium (Ca)
Magnesium (Mg)

Micronutrients
Zinc (Zn)
Iron (Fe)
Copper (Cu)
Manganese (Mn)
Boron (B)
Molybdenum (Mo)
Chlorine (Cl)

I think I must have been off sick on the day that my chemistry teacher covered Molybdenum because I’d never heard of it before!

Remember, none of these are optional. They are all required for healthy plant growth. So how do you know if your soil is deficient in any of these and how can you correct it?

The easiest way to get to know your soil is to do a nutrient soil test. Not the kind of test that you buy from the nursery that looks like a test tube but a test done by a laboratory. There are soil testing services (do a Google search) that will test your soil sample and tell you the levels of nutrients in your soil. If your soil is deficient in any of the nutrients above they will tell you and also recommend the amount and type of fertiliser to you need to add to correct it.

I’ve never had my soil tested but I plan to do it in the next few weeks. Autumn would probably have been the best time to do it so that I could add any corrections then but we were in the middle of a huge re-landscape then and so it wasn’t ideal.

Your soil is most likely to be deficient in the primary nutrients since plants use them the most. Calcium and Magnesium deficiency is most likely in acid soils. Zinc deficiency is usually associated with high pH soils.

You can also tell if your soil is deficient by looking for characteristic symptoms in the leaves of your plants. Here is a handy chart that helps diagnose nutrient deficiencies just by looking at the leaves of stressed plants.

If you are adding lots of organic matter to your soil, taking care to preserve soil structure and not planting too intensively then your soil should be balanced. Keep an eye on the pH of your soil too and make amendments where necessary. There is a reason why a pH of 6.5 is recommended for vegetable growing and that’s because most soil nutrients are available at that pH. Once your pH starts to move away from 6.5 certain nutrients become unavailable.

I hope this is interesting. I found the workshop enlightening. Soil nutrients is a subject that I’ve largely avoided over the past years because I thought it was complicated and, in truth, a bit boring. But I think now I can trace some of my major failures back to soil issues. So in the future I’ll be keeping tabs on the state of my soil.

I learned all kinds of useful facts about soil at my last Master Gardener session so I thought I would share some of it here. I already knew some things about soil, like clay soils hold water and can be difficult to work, and sandy soils tend to be harder to keep in one place and don’t hold nutrients quite so well.

I also knew that you could figure out what kind of soil you have by putting some in a jar with some water, shaking it and letting it settle over time. The layer at the bottom will be sand, the layer in the middle will be silt and the layer at the top will be clay. That way you can determine how your soil is built up. But what I didn’t know was the reason why.

As you can see from the photo above sand particles are huge compared to silt particles and effectively gigantic compared to the miniscule clay particles. That’s why the sand particle settle first, then silt, then clay. Because sand particles are so big there are large spaces between each particle and that’s why sandy soils don’t hold water – because the water flows right through.

Similarly, when it comes to clay soils the particles are so tiny that they stick together very tightly and let hardly any water through, that’s why they are often water-logged.

Sand, if rolled into a ball will not hold together. Silt, if rolled into a ball will hold together somewhat but then fall apart, and clay, if rolled into a ball, will stay in a ball because the particles are so small.

And then there is Loam. Lots of gardeners talk about it but what exactly is it?

Loam is the perfect soil. It’s what you’re aiming for in your garden. Loam is simply a soil that has equal parts sand, silt and clay. So it’s not too waterlogged, and it’s also free-draining. Look at the soil triangle above. You’ll notice that loam is in the middle. You are most likely to find clay particles in your soil that’s why it takes up so much of the triangle. Silt and sandy soils are less likely and they take up small portions of the triangle. But what you’re aiming for is somewhere in the middle with a little bit of each particle in your soil.

But what about organic matter? Well, organic matter is not really calculated in soil structure. Mainly because it’s transitory. You add organic matter, it breaks down into humus which is a kind of natural glue to strengthen and bind the soil but is not a permanent part of the soil. Gravel and rocks are also not included in this as they don’t contribute to the soil’s productivity.

When the sand, silt, and clay cluster together they form aggregates called peds which provide structure to soil. Organic matter helps bind these particles together. A well-structured soil is like a sponge allowing water in but also enabling it to leave when there is too much of it.

Because soil structure is so important it’s vital to preserve it when it’s attained. That’s why gardening books always warn against walking on the soil, as compaction ruins soil structure and also digging when the soil is either water-logged or frozen. This also destroys soil structure.

Last week I started the Master Gardener course at the Oregon State University. It’s 11-weeks of classroom learning followed by 11-weeks of practical gardening out and about in Portland. I’m so excited to be learning so much about gardening and being able to do it with people who are as enthusiastic as me about gardening. My plan is to select some of the most interesting and enlightening parts of the course and blog about it. I’ll file the posts under Master Gardener and there will be one a week. So it will be like you’re doing the course too. Well, sort of.