In this article
We know there's an abundance of different brands and types of potting mixes, so we've created this Potting Mix Buyer's Guide to help you decide on the best type of potting mix for your situation.
What is potting mix?
Potting mix is specifically designed to help plants grow in pots and containers. In particular, potting mix is generally a more open mix, which helps to get fresh air and nutrients to the plants’ roots (particularly important for seedlings).
NZ potting mixes are generally a mix of bark fines, pumice and a variety of fertilisers to ensure that plants have enough nutrients to grow.
How is potting mix different from other soils?
The main difference between potting mix and other garden mixes, is that potting mix is formulated to drain extremely well and may have a different fertiliser blend.
Potting mix differs from topsoil and topsoil blends because it is weed-free, is made from bark fines and pumice and has controlled release fertilisers in it.
Potting Mix vs Compost
The difference between potting mix and compost is that compost can be added to potting mix to enhance its nutrient content but you shouldn’t grow directly into it.
While compost has denser and more varied nutrient content than potting mix, it can’t support the root structure of plants and provides inadequate drainage.
We’ve already said compost is weed-free? I would delete it.
Potting Mix vs Garden Mix
The difference between potting mix and garden mix is that garden mix is used in raised beds, or in the garden directly, while potting mix is used on its own for plants in pots and containers including potted houseplants and window boxes.
Garden mix does not work well in small pots and containers as it tends to become compressed and waterlogged - potting mix has superior drainage and aeration).
This can reduce the air space around the plants’ roots leading to poor growth.
However, it can be mixed with potting mix to fill large pots and urns that need large amounts of mix.
Potting Mix vs Topsoil
The difference between potting mix and topsoil is that potting mix is commercially manufactured to meet plant requirements specifically for planting in containers.
Topsoil is mostly used for landscaping or to be added to other types of soil.
Unlike potting mix, topsoil is not weed-free. It will often contain decaying organic matter, sand, clay and other materials.
Blending potting mix with other soils
Potting mix can sometimes be mixed with garden mix or compost for outdoor potted plants.
When mixing potting mix with garden mix or compost l you should consider the type of plant you are potting and what soil conditions it thrives best in. This will help to determine the ratio of potting mix to garden mix and compost you will be using.
This is more relevant when filling larger pots or urns and adding compost to potting mix should be limited to 1 part compost to 4 parts potting mix.
What is potting mix used for?
Potting mix is specifically used for growing plants in containers or pots.
- It holds nutrients around the roots of the plants allowing nutrients to be continuously released as the roots grow and develop.
- The slow-release fertilisers in the mix the plant with the nutrients it needs as it grows.
- Its aerated qualities help the roots breathe and prevent decay helping to avoid root rot that can happen when plants are confined to small containers.
- Added pumice also improves drainage so plant roots do not hold water. In hot summer plants in pots may need a daily watering and a layer of mulch over the top can be beneficial.
- Potting mix is also used for strength and foundation to hold up the plant while it is small and fragile, allowing it to grow substantial root systems that will hold it up once it is larger.
What is potting mix NOT used for?
Potting mix is definitely not used for planting in large outdoor gardens or as topsoil.
This is because it is specially designed to drain well so that small plants in pots do not rot. Outdoors, this can mean drainage that is too effective, causing your garden soil to dry out.
For best results, we recommend using potting mix only when potting plants in containers.
Which plants grow best in containers?
Below is a suggested table of plants that will thrive in containers.
| Trees & Shrubs - (larger containers) | Annuals | Perennials | Flowering bulbs | Succulents | Fruits & Veg |
|---|---|---|---|---|---|
| Camelias Citrus Hebes Hydrangeas Bay Olive Evergreens Deciduous shrubs Maples Carpet Roses |
Lobelia Pansies ViolasPetunias Snapdragons Impatiens primulas polyanthus cylcamen |
Daisies Lavenders Geraniums Pelargoniums Verbenas Tropical impatiens Fuchsias Hostas |
Daffodils Tulips Freesias Hyacinths Crocus Begonias Dwarf Canna Lilies Calla Lilies Dahlias Lilies |
Burro’s Tail Cactus Hen’s & Chick’s Jade Plants Aloe Veras Ponytail palms Snake plants Sansevierias |
Strawberries Blueberries Citrus Dwarf fruit trees Figs Potatoes Tomatoes and other summer veg Lettuces Herbs |
Types of potting mix
There are many types of potting mix based on the conditions you are planting in and the plants you will be using.
Indoor potting mix
Indoor potting soil is specifically designed for indoor houseplants because it contains biochar and sandy soil which is great for drainage and nutrient retention. This helps prevent pests like fungus and gnats from hurting your plant.
Outdoor potting mix
Outdoor container or potting soil is meant for an outdoor container plant because it is made with fertiliser, peat moss, and sometimes compost, and worm castings.
This makes it a soil based potting mix, causing it to be heavier and able to resist environmental changes outside.
All purpose potting mix
This type of potting mix is suitable for any indoor and outdoor container plant, especially when repotting growing plants or setting up new ones.
It contains a general mix of compost, pine bark, perlite, and fertiliser that allow for drainage, aeration, and water retention.
Seed-raising mix
Seed-raising mix as the names suggests, is a potting mix with low nutrient levels, often made with perlite or coco coir with good drainage qualities. This encourages plant roots to branch out for nutrients, helping them develop quicker. Most mixes contain a fungicide to help healthy seedlings develop to ‘potting on’ stage.
Orchid potting soil
This potting mix is tailored to the fact that orchid roots are sensitive to root rot and require significant circulation and drainage. Made with ingredients such as coconut coir, fir bark, and charcoal, you can be sure that your orchids will stay healthy.
Organic certified potting mix
Organic certification means that an independent body, usually BioGro, has granted certification to the manufacturer of organic potting mixes that contain organic fertilisers and base ingredients.
Manufacturers are audited regularly and both inputs (ingredients) and manufacturing must comply with strict conditions.
Organic potting mixes are ideal for growing food in a chemical-free environment. However, because the fertilisers are not ‘controlled release' in the way that chemical fertilisers are, the mix should be topped up with a liquid organic fertiliser during the growing season.
How to store potting mix
Storing unused potting mix works best when we consider the lifetime of the fertilisers in the mix.
Short-term storage
If you have a surplus of bagged potting mix that you need to store for the next few weeks, you can place the bags in your garage, shed or under the eaves of your house.
Medium-term storage
In the event that you need to store the potting mix for up to two months, we recommend storing them in a dry, indoors, sheltered area away from the sun and moisture. However with fertilisers in the mix, there is a high chance of them deteriorating over a longer period, so extra fertiliser may need to be added.
Long-term storage
If you find yourself needing to store excess potting mix bags for another season, typically around 12 months, you can keep them in a dark dry area. But do remember that potting mix degrades over time, so once you take this out to use it again you will need to mix it with a new potting mix and extra fertilisers to be sure you are giving your plants the proper nutrients they need to thrive.
What to look for when buying potting mix
You need to make sure you are buying the best type of potting mix for the plants you are potting!
Daltons Premium Potting Mix
Daltons Premium Potting Mix is a versatile use mix perfectly blended for both indoor and outdoor container plants, as well as serving as a garden soil amendment.
Infused with controlled-release fertilisers offering up to 10 months of complete nutrient supply and trusted by professional nurserymen throughout New Zealand.
Order Online
Living Earth Organic Potting Mix
Living Earth Organic Certified Potting Mix is blend of bark, compost and organic fertilisers and is ideal for growing all types of plants in pots and containers.
It is a chemical-free mix, and is suitable for growing organic vegetables and fruit.
Order OnlineLook for high quality
Always buy a high-quality, potting mix for your container plants. You are looking for a healthy mix to provide the best aeration and drainage to feed your plants.
Colour: It should be dark brown to black in colour resembling ground coffee beans.
Smell: Its smell should be odourless with no trace of ammonia.
Texture: Its texture should be lighter and fluffier than your average garden soil.
Warning!
If your potting mix is light brown or dry and crumbly, it is likely to be unsuitable for potting.
How much potting mix do you need?
Calculating the amount of potting mix you need is a bit more complicated than other soils; you will likely have pots and containers of various sizes. The easiest way to calculate how much potting mix you need is by taking the volume measurements of the pot. Many pots will come with measurements on the label which can make this process easier. However, if you need to find out the volume of your pot you must first determine the shape (rectangular, round, truncated cone) and then you can find the volume with this easy formula.
Rectangular: volume = depth × length × width
Round: volume = 3.14 × Radius² × depth
Truncated cone (traditional flower pot): volume = (1/3) × 3.14 × depth × (r² + r × R + R²), where r is a radius of the base of flower pot, and R of top surface radius
Bulk or bagged?
Bagged potting mix is the usual choice for potting projects considering many pots and containers are small to medium-sized and require small amounts of potting mix.
Not keen to push bulk so much. obtain a quote is best. When purchased by the bag it is typically available in 25 and 40 Litre bags. However, sometimes bulk potting soil is for sale for larger projects and is typically measured in ⅓ of a cubic metre. If you order potting soil in bulk, some companies can get potting soil delivered directly to your house.
For bulk, get in touch with your local yard to arrange a quote.
Potting soil prices
Potting mix usually comes in 40 L and 25 L bags. There can be a wide variation in price - more expensive mixes contain a higher proportion of and/or higher quality fertilisersThe typical price for a 40 L bag is between $15and $25. The typical price for 25 L bags is between $10 and $15.
Frequently asked questions
What is the importance of potting mix?
Potting mix is made of various ingredients that provide a healthy environment for potted plants to grow. These mixes are designed to keep the soil from becoming too compacted, which can suffocate roots and impede the flow of water and nutrients.
Can you reuse potting mix?
It's normally fine to reuse potting soil if whatever you were growing in it was healthy. If your potting mix did have pests or diseases on your plants, it's best to dispose of the potting mix. Reusing potting mix means extra fertilisers and even more mix may need to be added. How to make potting mix for potted plants?
If you aren’t buying a premixed potting soil, you could mix 2 parts peat moss or coco coir, with 2 parts compost, 1 part perlite, and ¼ to ½ parts vermiculite to get a well made potting mix for potted plants.
Can seeds grow in potting mix?
Yes you can, but potting mix has a coarser texture than seed raising mix, and you'll often find chunks of bark in potting soil. For the best results starting your seeds, we recommend using a seed raising mix and then transplant your plants into the pot they will live in.
Can I use potting mix for vegetables?
If you are growing vegetables in pots, then potting mix is great for growing fruits and veggies in containers. However, if you are planting in a raised bed or garden, use garden or veggie mix which is more economical.
What potting mix is best for herbs?
Most general potting mixes will grow herbs easily.
Can I use potting mix for seedlings?
Potting mix is best used for seedlings that have at least two true leaves, ideally more. If you transplant seedlings any sooner than this, they may perish.
How long does potting mix last?
Opened bags of new potting mix can retain quality for around 3 months, but while it can be stored you will need to add more fertiliser.
Is potting mix dangerous?
Legionella longbeachae, a bacteria commonly found in potting mix, can cause Legionnaires' disease, a form of pneumonia. This disease is often caused by inhaling handling potting mix, soil or compost. use the advice of handling from DoH / However, the risk of this is very low.
What to do with old potting mix?
It can be dumped directly out of your containers and into established garden beds. It can also be used to fill in holes or eroded areas in a yard or be mixed into compost piles. it will not add any nutrient value to the garden and it will not improve texture of the soil.
Can you use garden soil in pots?
No. Garden soils are typically intended for use in the ground and contain minerals and organic matter. They are not a good choice for containers because the soil can quickly become compacted and waterlogged, reducing air space around the roots. This can lead to poor or stunted growth and root rot.
Can I use potting mix in my garden?
No, it is of a different texture and composition specifically for container growing.
How do you use compost in potted plants?
You can add compost to pots. In a potted plant mix the general rule of thumb is twenty percent compost.
What is the best potting mix for indoor plants?
The best type of potting mix for growing indoor plants contains sterile garden soil and compost, peat moss (or coconut coir) and perlite.
What is the best potting mix for vegetables?
There are a number of potting soils that are great for growing vegetables. If you are looking for the qualities of a great vegetables growing potting mix look for one with loamy qualities. Organic certified potting mixes are ideal for this purpose.
What is the best potting mix for flowers?
There are a number of potting soils that are great for growing flowers. If you are looking for the qualities of a great flower potting soil look for those with peat moss, pine bark, and perlite and slow release fertilisers as the main components.
Should I use seed raising mix or potting mix?
If you are starting plants from seed, a seed raising mix is your best bet. Once the seedlings have two true leaves, you can transplant them to a container that has potting mix in it.
Should I wet the potting mix before planting?
Yes! Water the potting mix thoroughly before you plant. Use a slow, steady stream of water to avoid soaking the mix.
Is potting mix good for outdoor potted plants?
Using a good quality potting mix is a simple way to get your outdoor container gardens off to a great start. Quality potting mix will help your container plants thrive.
Do I need to add soil to potting mix?
Since potting mix is intentionally created as a soilless medium, there is no need to add soil to it when potting plants.
Does it matter what potting mix you use?
As long as your potting mix has the essential ingredients and nutrients for the type of plant you are growing, it doesn’t matter what brand you buy. The only exception would be if you wanted an organic garden, then you would need to make sure your potting mix is certified organic.
How long can you use the same potting mix?
Plants such as shrubs and trees can survive for years in the same soil, provided the mix is topped up and regular fertilising happens. Watering is essential as well.
Do I need to add fertiliser to potting mix?
Fresh potting mix contains all the necessary fertiliser and nutrients your plant needs. However, frequent watering of potted plants can cause the nutrients to deplete over time. As a result, we recommend that you apply a water-soluble fertiliser such as fish emulsion or seaweed every two weeks during the growing season.