General gardening topics

How to make seed compost for starting seedling

Our site is reader supported, this means we may earn a small commission from Amazon and other affiliates when you buy through links on our site.

This is the season for seedlings. Now is the time for germinating in your home or greenhouse, which of course requires a good seed compost. The problem is most compost types including multipurpose compost you can buy from garden centres and nurseries are not ideal seed starting mixes. You have probably had some plants that no matter what you did, just did not germinate. They seemed overly watered on top but dry to the bones down below. 

The cause? If the compost mixture isn’t right, it can lead to bad water absorption, something that proves fatal to your new seeds because they can rot before they started. If the nutrient content is wrong, it will hinder root growth and seedling need very little nutrient value at first. 

Plus, it’s expensive. No matter where you look, high-quality compost is expensive. 

To that end, knowing how to make seed compost for starting seeds can prove very useful especially if you are going to germinate from seed, season after season. 

The Recipe for germinating seeds

To make anything, you need the perfect recipe. Seed starting mix needs to be low in nutrients, hold on to moisture without becoming soggy, and it needs to be light and fluffy so the roots don’t can penetrate and spread without much resistance. 

Getting the base mix right

Start with the base of your mixture which should contain two parts compost. When reading this compost mix, be advised that the parts are based on volume, so whatever amount you are making, you can keep to the same volume and ratio. We recommend just using a large jug to scoop the correct amounts in equal volumes.

Use 2 parts compost that has been sieved with a riddle

Compost will release nutrients slowly, something the growing seeds need. Break apart the compost with your hands but we recommend using a compost riddle to make it as fine as possible. 

Mix the compost with 2 parts coir

Mix in two parts coir, or coconut fibre. This is what often lines store-bought wireframes for hanging baskets and it is a great alternative to peat moss. and we are always trying to find good alternatives to peat to do our part to help the environment. While peat moss is the normal additive here, it is not a sustainable product to use while coir is which is why we recommend it. 

If you order coir and it arrives in a block form, you need to rehydrate it in a bucket of water until it breaks apart. 

CANNA Coco Professional Pro Soil 50L
  • High quality, cleaned and pre-treated coco coir ideal for pot culture or other bulk uses
  • Very easy-to-use and gives great results
  • A pure, organic product with a homogeneous structure and has had a full buffering, eliminating the side effects of growing on coir
  • Free of harmful viruses and soil diseases, thanks to CANNA's unique production process
  • Complex water/air system that that provides the ideal conditions for growing plants

Finally, add one part perlite to the mix

Lastly, add one part perlite to improve air content and lighten the mixture. Sand is an alternative to perlite, but it will produce a heavier mix.

PLANT!T Perlite 100L Bag
  • PLANT!T Perlite can be used for soil conditioning – increasing aeration and drainage in heavy, hard to manage soils^Repairing/laying down lawns – PLANT!T Perlite gives additional aeration and drainage when raked into spiked holes^Planting trees and shrubs – loosens and aerates soil to encourage root development^A natural, pH neutral and sterile growing medium derived from volcanic rock^Aid nutrient uptake and improves plant health and growth. Available in 10L and 100L bags

Mixing the compost mix

When you have all your ingredients, you need to mix them thoroughly. Use your hands for better tactile engagement and thoroughness; the more consistently mixed the better. When you are done, store your mix in a lidded container or thick plastic sack in a cool, dry place. 

Germinating seedlings

When it comes time to use your mix, moisten it so that it is not sodden, but not dry. Use recycled containers, seed trays, or module trays and gently press down on the mixture as you fill in your container of choice. Consider using a heated propagator to improve the germination rate and speed up the process.

Stewart P035B Essentials Electric Propagator, 52 cm - Black
  • 52 cm heated propagator
  • Non thermostatic - simple on-off control via mains
  • Clear cover with adjustable ventilation
  • Adjustable ventilation panels for humidity and air temperature control
  • Sealed unit with an economical 22 W heater - insulated to retain heat within the propagator

Be sure to sow the seeds according to your packet instructions and water afterwards. Rest assured this mixture can be used as you transplant young seedlings and is something you can make year after year.

Would you rather buy seed compost?

Bestseller No. 1
John Innes Seed Sowing Compost by Westland Garden Health 10l
  • Perfect for bringing seeds to life
  • For fast, healthy germination
  • Fine texture
  • Helps retain moisture around seed
  • Balanced nutrient supply for seedlings
Bestseller No. 2
Levington John Innes Seed Compost 30L for Sowing Seeds, Striking Cuttings, Delicate Seedlings
  • Ideal for sowing seeds, striking cuttings and delicate seedlings
  • Specially developed, with a high phosphate formula and 14 vital minerals for optimum root growth
  • Traditional mix of loom, peat, sand and fertiliser
  • Perfect for all seedlings
  • Approved by the John Innes Institute
Bestseller No. 3
Gro-Sure Seed & Cutting Compost Pouch 10L
  • ADDED SEAWEED NUTRIENTS - For healthy growth
  • SUPER FINE GRADE - Specifically formulated to grow from seeds
Bestseller No. 4
GRO Sure Seed and Cutting Compost 10L by Westland
  • Improves germination by 25% for the best start.
  • Super fine grade Improved aeration & drainage.
  • Seaweed & nutrients for healthy growth.
  • When trialled with standard seed & cutting compost and standard seed
  • 10L bag

Last update on 2021-05-07 / Affiliate links / Images from Amazon Product Advertising API

Welcome to my site, my name is John and I have been lucky enough to work in horticultural nurseries for over 15 years in the UK. As the founder and editor as well as researcher, I have a City & Guilds Horticultural Qualifications which I proudly display on our About us page. I now work full time on this website where I review the very best gardening products and tools and write reliable gardening guides. Behind this site is an actual real person who has worked and has experience with the types of products we review as well as years of knowledge on the topics we cover from actual experience. You can reach out to me at

Write A Comment