Soil and Compost
What is soil?
Soil is one of the most precious and important things on earth. Without it there can be no life, it’s that simple. But what is it exactly?
Soil is made up of minerals (fine particles of rock), organic matter (decomposed plants and animals) and living micro-organisms. For a healthy soil in which plants will thrive, we need a good balance of all three of these elements.
Different kinds of soil
Soil will differ from one place to another because the minerals will be different. Some soil will be sandy – made up of relatively large particles of minerals, which allow lots of drainage, and some will be clay based – made up of much smaller particles, which stick together to make it less free draining. Most soil is somewhere on a scale between the two. Typically, North Leeds has quite heavy clay soil, to do with the geology of our area.
Soil also differs depending on how much organic matter it includes. In a garden we can improve the soil by adding organic matter like garden compost and well-rotted manure. This will also help to improve the level of micro-organisms in the soil. While a few plants – some wild flowers and some Mediterranean herbs for instance – thrive on ‘poor soil’, ie soil that isn’t rich in nutrients, mostly our garden plants need good healthy nutrient rich soil to thrive.
What is compost?
Compost is rotted organic material.
Garden compost V Commercially sold compost
Garden compost – rotted down garden and kitchen waste – is a mixture of lots of different kinds of vegetable (and in some cases, animal) matter. It is high in nutrients and bacteria.
Commercially sold compost also contains rotted vegetation, but tends to be less varied. For instance, it might be entirely made of rotted bark chippings or choir. Commercially sold compost also frequently contains peat, contributing to the destruction of peatland habitats (more of this later), though this will be outlawed in the UK by 2025. Some commercially sold compost also contains loam – that’s the minerals and organic matter that makes up the non living parts of soil.
Commercially sold compost is often sterilised – which kills the bacteria and fungi. This is good for seed sowing, which don't need too many nutrients to germinate. But it doesn't hold the same vital components as soil.
Garden compost is fantastic for mulching or digging in to your garden soil, or as part of a potting mix for potted plants. It adds nutrients and bacteria and fungi to help make your soil healthy and help healthy growth of plants. It also helps to retain water in very sandy well-draining soil, and open up dense clay soil that doesn’t drain well. So it’s magic stuff, and every garden should have some. And of course, once you’ve set up a compost heap or bin, it is free. It’s not so good on it’s own for sowing seeds, as it tends to be too nutrient heavy which can burn tender shoots and leaves, and can carry diseases which could kill off a very young plant. And very few gardens and households produce enough compost to rely on it entirely. Even Kew Gardens ship in horse manure!
Commercially sold compost is great for sowing seeds – because it tends to have less nutrient content, and fungi and bacteria. On it’s own, it’s not so good at holding on to moisture, so may need other things added to it especially if you are using it in a pot, such as loam (for a long lasting outdoor pot) or vermiculite which is especially good for houseplants, and for window boxes and hanging baskets which tend to dry out quickly, because vermiculite is very light, but holds on to a lot of water, slowly releasing it back into the soil. Perlite does a similar job.
The Green Yard’s Houseplant potting mix contains commercially produced coir based compost, vermiculite and perlite so that it retains moisture whilst remaining free draining – which most houseplants will thank you for! We recommend you use a purpose produced houseplant fertilizer to help your plants thrive.
So, there is a place for both commercially made bought compost and the glorious stuff you make at home. You are unlikely to produce enough garden compost to both mulch your garden beds and use in pots. Most gardeners agree, it’s best to heavily mulch a small part of your garden with whatever garden compost you have once every 5 years, than to spread it thinly over everywhere every year.
And what about manure?
Good question! Manure is a superb source of nutrients and will do wonders for your garden. But it must be well rotted. So, if you are buying it directly from a stables or farm, make sure it isn’t fresh! If you have space in your garden, pile it up til next year, and then use it.
What kind of compost do I need for my plant
Different plants need different soil. If you are growing in the ground, it is best to consider what kind of soil you have and then find plants that will like that. So if you have heavy clay wet soil, grow things that like their roots being kept moist, such as bog plants. If you have light sandy well-drained dry soil, grow things that like that. You can modify the soil environment somewhat, by adding organic material (compost, manure), but in the end, the plants will be happiest if they are suited to your native soil.
If you are planting into pots you can mix things up a bit. Consider where your plant originates from. Is it a species that’s native to a Mediterranean-type climate? If so, make up a compost that is well draining by adding grit, or even sharp sand (make sure it’s sharp sand, because the smoother grained play-sand and builders-sand will stick together and not drain at all well). If it’s a species that prefers damp conditions, make sure you add lots of well-rotted compost in to ensure that it’s able to hold the moisture.
If you are potting up a houseplant, consider where the plant is from. Most of our most familiar houseplant species originate in tropical rainforests. They like humidity and they like to be well watered, but they do NOT like their roots sitting in water. There are some exceptions to this, but a good rule of thumb is water but don’t over water.
The Green Yard houseplant potting mix is specially formulated to be well draining, so roots don’t rot, but also moisture retentive so that the plant doesn’t dry out quickly.
Cacti and Succulents
Let’s not forget the desert plants though. Cacti and succulents with a few notable exceptions, are native to arid climates and store water in their leaves or stems, so they can go for a long period of drought. They really won’t thrive in soil that is always damp and will thank you for a compost that is very free draining.
The Green Yard Cactus and Succulent Potting Mix contains grit sand and perlite so that the plant never sits in soggy compost.