In the UK we start planting seeds for the new year around February and March, depending on the climate. A lot of people get confused about when to start, what to do and how to care for your seeds so I have put together a useful guide which I'm hoping will help you along the way!
When to start
The first question many gardeners ask is when to start growing your seeds. It's mid-February when writing this, it's a lovely fresh morning and is quite warm; being 8°C. Days like today can be very misleading and could easily get the average gardener eager to start their seeds. But is it the right time?
Not really!
The best way to know when to start seeds is to work out your last frost date (on average) in your area, as seeds do not need light to germinate they need heat it is vital that you avoid frost or your hard work will be wasted. Although you can start seeds indoors, in heated greenhouses and in propagators; for the average gardener this is not attainable.
Where I am in the UK my average last frost date is May 1st to May 10th and therefore it wouldn't make much sense to start seeds in an unheated area prior to this date. However, there are some exceptions and mitigations to this rule.
Most tender and half-hardy flowers and veg can be sown in spring, for planting out in late spring and early summer. Fast growing veg such as salads and spring onions can be sown in the summer. Winter and early spring salads and veg can be sown in autumn for a crop in the winter and veg that needs a long growing season such as chillies can be sown in winter.
What to do if you want to start your seeds early?
If you want to start your seeds early there are a few methods that are proven, which you could try
- Grow lights and heaters - heaters will warm your seeds to allow them to germinate, where as grow lights will help with growth after germination
- Heated greenhouses or propagators - These will keep the temperature up during the colder nights to reduce the risk of frost damage of your seedlings
- Seed germination in a airing cupboard - airing cupboards are a brilliant way to start the germination of seeds, if you dampen a paper towel, put the seeds onto it, fold it up, put it in a container and place it in your airing cupboard your seeds will germinate a lot quicker. Germination needs heat and water after all
- Growing seeds in containers on your windowsill - if you want to start seeds like tomatoes and peppers to get a head start then you can place your containers on your windowsill in your home, this will provide more light and heat than a typical greenhouse and will allow early growth.
Just bear in mind that with these methods if the sun isn't out your plants can get leggy searching for the sun, which will make them weaker when translating out. There is come argument that later started plants will catch up and become stronger than earlier started plants, but this is not proven so why not try both and find out!
What can I grow ahead of time?
You can grow a number of seeds indoors ranging from tender crops to slow growing crops. Some examples are:
- Tomatoes
- Chillies
- Courgettes
- Broccoli
- Sunflowers
- Nasturtiums
- Sweet peas
- Basil
- Celeriac
How to start planting and germinating
The rule of thumb I follow when planting seeds is to plant them twice the depth of the size of the seed into the soil in soil blocks. This allows for enough depth for the seedling to root properly and ensured that there is no transplant shock later on in life.
There are of course other methods, and each seed packet will clearly describe depth / spacing of each seed when planting. You can also use compostable containers to also reduce transplant shock like paper mulch, toilet rolls and normal plastic pots such as seed trays and modular trays.
We grow our seeds in soil blocks to ensure there is no transplant shock at all, and no need to pots and containers.
Once your have sown your seed then you can place the pots / trays in a heated and frost free greenhouse, on a windowsill, in a conservatory, or in a heated propagator.
Smaller seeds can be sprinkled on a seed tray and topped with compost, where as larger seeds will need to be pressed into the compost individually.
Where to grow your seedlings
Seed packets will give detail of whether your seed should be sown indoors our outside. The normal reason for this is transplant shock, so if you are happy growing in soil blocks or compostable containers than most seeds can be grown indoors.
Different seeds need more temperature to germinate, this should be written on your seed packet. For example tomato seeds need more than 21°C to germinate so right now would not be a good time to start them in an unheated greenhouse.
When to plant outside
After the last frost has absolutely past, around May time in the UK, are you seelings have grown strong and sturdy you can plant them in the final position in the garden.
Make sure to harden them off for a week or so before planting (take them in and out so they get used to be being outside), water sell and plant the seelding in a hold in the ground.
Make sure to press the soil around the seedling down to ensure there is no air holes for water to pool.
Watering
Seeds and seedlings don't need as much water as larger plants, so make sure you water gently to avoid over watering and dislodging of the seeds.
You can also stand the containers with holes in the bottom on a tray of water, this will allow the soil and roots to take up the moisture from below.
We have found that the best way to water our seedlings is slow and steady with a pop bottle watering adapter. We've been using these for a number of years now and they work perfectly
 |
Watering nozzle for plastic bottles |
Problem solving
There are a few problems that you can encounter when growing seeds. I have listed some below for consideration.
My greenhouse isn't heated but I want to start seeds early
You can grow your seeds inside the house, this will give you the heat you require. Or if this is not an option then you can cover your seeds at night to keep the frost off. We use sheeps wool for this!
Mouldy compost
Mould growing on compost is not always a bad thing, it means your compost is alive. However, the best way to avoid excess moss / mould is to water from below, so you don't over water the seeds that are not big enough to drink it all up.
Leggy seedlings
Leggy seedlings that are very thin and tall tend to occur when growing indoors when sufficient light isn't available. This is because your seedling is searching for a light source. Try pruning off the top to encourage bushing out, rather than growing up.
FAQs
Why have my seeds not sprouted?
There are many reasons for lack of germination, I have listed a few below
- Too much or too little water - seeds need a regular supply of water but not in great quantities. Your compost should be slightly damp and never dry.
- The wrong temperature - as discussed above different seeds need different temperatures to allow them to germinate, if you too cold or too hot then your seeds wont germinate or the seedling will dry out too quickly
- Incorrect planting depth - some seeds need light and some seeds need darkness to germinate, so if you plant your seed too deep or not deep enough they may have issues when trying to germinate
- Seed age and storage - if your seeds are not stores in the correct conditions, have got damp and rotten or are just too old then you will have a reduced chance of germination. That is not to say to throw out seeds that are pest their "sell by date", but just know that seeds do not always stay good.
I've grown my seeds in a tray, do I need to separate?
Yes! once your seedlings have a least two pairs of leaves they are big enough to separate out into individual pots to allow them room to grow. This is called pricking out. Don't delay in doing this or your seedlings will become more prone to fungal diseases and roots becoming intertwined.
Products we recommend
 |
|
 |
|
 |
|
 |
Reusable bottle drop irrigation |
 |
Seed sower |
|
Watering nozzle for plastic bottles |