Tips from Olle Garden Bed: Optimum Potting Soil - Dirt on Dirt – Ollegardens website

Tips from Olle Garden Bed: Optimum Potting Soil - Dirt on Dirt

What makes good potting soil for outdoor plants? When planting a plant in a raised garden beds, the potting mix is supposed to provide three things:

Keep water and nutrients around the roots of plants.
Soil is a reservoir for these key life elements in a container garden.
Provide enough air for growing roots.

You should make sure that the soil in your planter is not compacted and has plenty of air. Roots need air, too! When the roots don't have enough to breathe and begin to rot, the plant won't grow properly.
raised garden bed
To support your plant, provide anchorage for the roots.

The soil mixture needs to settle around the roots of the plant and help hold it in place, lest it be blown over by the first gust of wind. However, it also needs to be light enough to allow water and air to always be present under the soil surface so that the roots of the plant have a balanced atmosphere to grow in.

Therefore, given that a good potting mixture can do these things, any number of different materials can be used. I know many gardeners use soil from the garden in their POTS, and some make their own compost and add it to their containers. You can do any of these things, but if you're making your own potting soil at home, you'll also need to change the way you water and fertilize for best results. There are a million ways to mix potting soil, from hydroponics to sewer sludge, but the potting soil you buy at most garden centers is a simple mixture of some basic items.

Rules of thumb for choosing potting soil
The potting soil used in the container should be light and fluffy.
Look for potting soil made of sphagnum moss, pine bark, and perlite or vermiculite

Fertilizers can be added in the form of "starter" or slow-release preparations. Adjust your fertilization practices accordingly

The potting soil may be treated with moisturizing treatments, and if you use potting soil that contains these substances, you may need to change your watering pattern.

Potting soil composition

Most potting soil you buy at a garden center is made up of three basic ingredients: sphagnum moss, pine bark, and perlite or vermiculite (which provides air space).
raised garden bed
Sphagnum

Sphagnum moss comes from peat bogs in the northern United States and Canada; This is generally considered to be a higher quality sphagnum moss type. There are some peat bogs in the southern United States, but they are generally considered to be of slightly lower quality. Sphagnum moss provides excellent moisturizing quality and provides good air space for healthy growing roots. This is sometimes the best potting mix for acid-loving plants such as rhododendrons or hydrangeas, however, sphagnum moss itself is too acidic for most flowering annuals. Therefore, it is usually best to use a mixed potting mixture with all three ingredients. You can use straight sphagnum moss as a potting mix, but be careful not to overwater. Sphagnum moss itself can keep plants wet for a long time after watering them.

Note: If you buy a bag of straight peat moss and it is very dry, you may find that it repels water. If you encounter this problem, the best thing you can do is soak the peat moss in the bag you purchased or in a wheelbarrow or bucket. Usually soaking it overnight will saturate things completely and then make them easier to use. Once saturated, it usually returns to a water-holding state with no further problems.

Pine bark

Pine bark comes from paper mills across the United States and Canada and can provide some moisture and fertilizer retention, as well as more air space. Pine bark alone does not provide enough of anything to really support plant life (except possibly orchids, see special mixes below), but once it is mixed with sphagnum moss - pine bark adds a new dimension and helps extend the "life" of the potting mixture by relatively slow breakdown.

Perlite and vermiculite

Perlite and vermiculite are both of volcanic origin, and both are put into the potting mix to provide extra air space and reduce weight, so the potting mix is not too dense and heavy. Perlite does not provide any nutritional benefits, and fluoride can be collected if it is present in the water. This means that fluoride concentrates after a while and can burn the leaf tips of some houseplants, such as dragon's blood and spider plants (chlorophyll). There are very few problems with any outdoor flowering plants, so don't worry if it's in your potting soil unless you're planting these plants. Vermiculite is a bit different because it contains a lot of water and also holds fertilizer for a while - helping to hold nutrients around the roots of the plant instead of washing off the bottom of the pot. There's even a soil mixture that recyles polystyrene foam for the same purpose as perperite and vermiculite, which is also nice, but eventually the foam rises to the top of the pot and blows in the wind, which can be a little annoying.
raised garden bed
To recap:

Sphagnum moss provides moisture and nutrient retention.

Pine bark provides anchorage, some nutrient and moisture retention and air space.

Perlite and vermiculite provide most of the air space in the soil.

Potting the soil with fertilizer

You are increasingly seeing bagged potting mixtures with prominent improvements on the bag. One of the more common ways to enhance potting soil is to add fertilizer to the mixture or mix slow-release fertilizer into the soil. Both are good ideas and help make things easier for you as a gardener, but there are a few things you should know.

The "starting charge" of fertilizer means that the amount of fertilizer in the potting mix is minimal, but it is minimal and does not mean that you will never need to fertilize. It just means you don't need to fertilize right away. Most starters disappear from the potting soil after two or three watering sessions. Starting the charge can help you plant, but you still need to fertilize regularly.

The slow-release fertilizer in the bag means you have more fertilizer to help your plants transition to their new home, but it rarely lasts past the first month. Therefore, in addition to the fertilizer in the bag, you need to make sure to fertilize regularly. One problem we see with this slow-release fertilizer is that if bags of potting mix are left or wet and sitting for a long time, the fertilizer in the potting mix can be released inside the bag and then when you plant flowers they can burn with too much nitrogen (similar to the problem with using manure products). Therefore, if you are buying potting mix with added fertilizer, check to make sure the bag is not wet and that the potting mix does not look like it has been sitting for a long time.

Moisturizing treatment

As with fertilizer add-ons, many potting mixes are starting to add moisturizing gels and chemicals. Again, this may help reduce watering throughout the season, and there really are no downsides.
You need to be extra careful not to overwater while the temperature is still cool, as the soil will not dry out as quickly as you are used to. You also need to realize that most of these "humectants" will not allow you to leave and keep everything in good shape in three weeks. Soil water retention breaks down with the seasons, and by mid-to-late summer, it may no longer be useful. So when you need water holding capacity the most - when it's really hot - it may no longer work.

Note: Just because the potting mix is moist doesn't mean the plants don't need fertilizer, many gardeners live where there is enough rain to keep the potting soil moist, however, you still need to make sure the plants are regularly fertilized to grow well. Plants can starve to death in moist potting soil, especially if there is a lot of rain that washes nutrients out of the soil.

Potting soil with garden soil, manure and mulch

When it's mixed with many other options, going to the garden center and trying to pick out the potting mix can be very confusing. But for simplicity, just buy potting mix for your container (look for a bag that says soil-free potting mix); All other bags are used for gardens or landscaping.

Garden soil is essentially potting soil with many other heavier and cheaper additives (such as compost, sand, clay, and various other things), depending on the manufacturer. It "can" be used as a potting mix, but when it dries you run the risk of smudging and pulling away from the sides of the pot, generally garden soil is meant to enrich the garden.
raised garden bed
Manure products are great for outdoor gardens because they are high in nitrogen, but not so great for POTS because all that nitrogen will burn your flowers instead of fertilizing them. If not used as a chemistry lesson, fecal products need to be diluted into your landscape at about the rate of one part manure to two parts landscape soil. Applying fecal based soil amendments directly to the roots of landscape plants or flowers often causes all roots to burn and can actually delay the plant from getting off to a good start in your garden. So be careful with them! Also, most faec-related products contain a lot of sand, which makes them heavier - too dense to use well in containers.

Mulch is usually a log product (bark, wood blocks, chopped wood, etc.) that is intended to be applied to the surface of the soil to help prevent moisture from evaporating, thus keeping garden and landscape plants moist for longer, with less water and fewer weeds. Since they are log products, they do not mix well into your pot. Log products absorb all the available nitrogen in the soil as they decompose, which means your plants look hungry and greenish-yellow because they can't get enough food to grow. Place mulch products on the soil of your garden and landscape. They are excellent for reducing water loss and, if applied thickly enough, can add some protection to annual weeds.

Mass ≠ weight

Many consumers confuse heavy potting soil with good potting soil. In most cases, when a bag of potting soil is very heavy, there are two reasons; It is either water-soaked or contains a lot of sand. In either case, this is not a good thing. If the potting soil is soaked, it will begin to break down in the bag - losing all air space and becoming compacting, with the risk of carrying root rot in addition to being nearly impossible to get into your car. Adding sand to the potting mix is another problem. Unless you are growing cactus, it is generally not a good idea to add sand (providing anchorage and some air space). Often, sand is added to the potting mixture simply because it is an inexpensive filler. Sand is used in place of more expensive ingredients, such as sphagnum moss or pine bark. If you live in a very windy area, a little sand can help keep the plants in place, but generally it's not needed.

Fungal growth on potting soil

Most of the prepared soil bagged and sold at garden centers and houseware stores is prepared months before the actual sale. Usually, these soil mixes are composed, sterilized, or at least heat-treated to eliminate any diseases, weed seeds, and other pathogens that will ultimately affect what you're going to plant and grow in the soil. When you open the bag and use the mixture, you expose sterile soil to a variety of native fungal spores in the environment in your home and garden. Sterile soil is the perfect home for these fungi (or molds) because there is no competition for the organic materials that make up the soil mix. These fungi grow rapidly, especially when given ideal growing conditions (which seem to be the same conditions we want to plant new spring plants). Under normal outdoor growing conditions, fungi are usually short-lived. Dry soil mixture, exposed to sunlight, and simply exposed to other competing organisms, the mold disappears through rapid consumption.

Most of the time, the presence of these soil-growing molds means nothing to the health of the plants you're about to plant; Except maybe the soil is too wet or there's too much organic matter. If you want to eliminate mold problems, open the bag and spread it on a sheet or cloth a few days before use, expose it to sunlight, and then rebag or place it in a soil bin while it dries. You can use soil with confidence, whether it's fresh out of the bag or "conditioned and dried."
raised garden beds
Mixed potting soil

As with all aspects of gardening, there are so many different things people do successfully that some gardeners literally vow to mix their own potting soil with everything from lawn clippings to fish heads to powdery clay. Plants are very forgiving as long as you adjust the watering and fertilization to match your mixture, and in some cases will do better using a custom mixture, so feel free to experiment.

Have you ever run out of one type of potting soil during planting and had to switch to another in the middle of a large container? I know I do. If you find yourself in this situation, I have a hint for you. Make sure to mix both types of potting soil as much as possible. By mixing them together, you can get an even mix of potting soil and your plants will do better. If you just pour completely different potting mixtures over another potting mixture and don't mix them, your plants will have a hard time growing down through one mixture and into the other if the two mixtures are different enough. There are many reasons for this, and instead of turning it into a physics lesson, take my word for it - if you find yourself having to switch between containers and mix potting soil. Your plants will thank you.

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