How to plant seeds in a flower pot

How to plant seeds in a flower pot

Planting seeds in pots

Planting seeds in pots

There are 3 main ways of sowing seeds:

  1. Sowing directly into the soil where they will grow.
  2. Sowing them into modules
  3. Sowing them into flowerpots. (or other containers) 

Here we are going to talk about sowing seeds in plant pots, flower pots or containers.

Here are some of the advantages of using pots:

 1. No weeds: You can be certain that the only seeds in the soil are the ones that you want to grow so there is no weeding or competition from weeds. 

2. Portability: Pots are portable and they can be moved around. For example moved into warmer or sunnier places or moved away from the cold if necessary. It is good for young seedlings  to have some air movement to strengthen the stems and also to have some direct sunlight. Plants tend to lean over to face where the light is coming from so you can move them around if light is coming from a narrow source.

3. Preparation: The purpose of growing seeds in pots is to raise small vigorous healthy plants.  When they are eventually planted into their final growing place as healthy robust plants all weeds can be destroyed at the moment of planting. If a mulch is applied immediately after planting our plants will have no competition and very little weeding will be necessary.

Which seeds are not suited to being sown in a flowerpot? 

I don’t plant very big seeds such as broad beans in pots. Some plants hate being transplanted so it is best to sow them where they will grow. Examples of these are root crops such as  carrots and parsnips. However if seedlings are handled very carefully they can be planted in pots. Radishes germinate very quickly and are very vigorous so it is best to plant them in the field. 

What type of soil should be used in the pot? 

The most important part of the soil in the pot is the first 3 cm. I fill up the flower pot with any old garden soil to within about 10cm from the top of the pot. Then I use some commercial potting compost soil from a  garden center to within 1.5cm from the top.  The soil right at the top should be fairly fine without any big lumps and it must be totally sterile. You can make your own seed compost for this purpose by putting some soil in a microwave or heating it up in a pan and then passing it through a sieve.  I tend to buy specialized seed compost from the garden center if they have any.

How to sow the seed? 

The most important factor is the depth that you put the seed. Very small seeds tend to  to be left on the surface and bigger seeds are planted deeper.   It often tells you on a seed packet the depth they should be planted. Some seeds need light to germinate whereas others will germinate in the dark.  Many people say that you should sow the seeds on the surface then cover them with other soil to the recommended depth. I tend to put the seeds on the surface and then mix them in with the end of a pencil so that most of them are more or less the correct depth. 

How long does germination take? 

Normally between 7 days and 3 weeks. The time is very dependent on temperature. Plants that need high temperatures to grow like pepper and aubergines like a high temperature say 20C. Cold tolerant plants such as cabbages will germinate at 8C.  The rate of germination depends on how old the seeds are.  In time the germination rate of a batch of seeds goes down until eventually they are all sterile. Below is a viability chart for common seeds.

  • 1 year: onions, parsnips, parsley, salsify, and spinach
  • 2 years: sweetcorn, peas, beans, chives, okra, dandelion
  • 3 years: carrots, leeks, asparagus, turnips
  • 4 years: peppers, chard, pumpkins, squash, watermelons, basil, artichokes
  • 5 years: most brassicas, beets, tomatoes, aubergine, cucumbers, celery, celeriac, lettuce, endive, chicory

What are common mistakes when planting seeds?
If you look at the pictures of novice gardeners on facebook, the biggest mistake is letting the seedlings go leggy.  Being leggy means having a very long thin stem. This is caused by having insufficient light and maybe being too warm.  A 10cm long seedling with a tiny thin stem and 2 small leaves at the top will most likely die very soon.  As soon as  seeds germinate they need lots of light and if they have been put in a high temperature to germinate they should be put in a cooler place. Seedlings grow stronger if they have some air movement which will make them sway around and strengthen the stems.  People growing plants inside in artificial lights use rotating fans.

The most common problem with seedlings is damping off. This is when the seedlings start to die and rot for no particular reason.  It is caused by  fungus or mould that thrives in cool, wet conditions.   If you have this problem, use sterilized pots or trays with good drainage and use clean new potting soil to prevent damping off. Pots can be sterilized with bleach and soil can be heated in a microwave  or a pot. To get complete sterilization,  you should heat the soil to between 80 and 90C for 30 minutes.  By the way, heated soil smells terrible. 

What to do with the seedlings? 
You have to wait until the seedlings are big enough to be transplanted. Generally speaking, seedlings should be more than 3 centimetres high. Seedlings can be either planted into small pots or modules or planted into the ground. 

Inverna Winter lettuce

Inverna Winter lettuce

The image above is of winter lettuce. It has actually been in the pot for some time. I have already potted up many seedlings from this pot into modules. These seedlings are big enough to be planted into the ground or into little pots. I would normally transplant the seedlings when they are smaller than they are in the photo.  In the background of the photo, you can see plastic modules. Seedlings can be planted into modules to let them get established.

Don’t forget to label your pots very clearly. You will need a permanent marker. Garden centres sell labels with a special pencil which will not become illegible.  In the past I have made home made  labels out of recycled  plastic bottles.  

How to transplant seedlings?
The only tools I use for this job is my index finger or if the seedlings are small I use a pencil. First I plunge my finger or a knife into the pot  to bring up a clump of seedlings. Then a seedling is pulled away from the clump. I only touch the seedling by the end of one of the leaves.  A hole is made in the place where the seedling is to be planted with a pencil or a finger and the root is lowered in. Afterwards, the soil is very gently  firmed down, then the seedling is watered in with some water from a cup or given a squirt from a spray. The seedling should not be lying down on the soil. The leaves should be in the air. They will take 2 or 3 days to get established. Some of them may die. In that case, just transplant another one from the mother pot.  This is a very pleasant activity on a sunny day. Make sure you listen to music while doing this activity. I find reggae is very suitable. 

Luke Jayne and Ditte transplanting seedlings

Other Comments
The soil that seeds are planted in does not  need any fertilizer. Once the seedlings have been transplanted, they benefit from some nutrients. They seem to like dilute shit tea. Just put some manure in a  bucket of water to soak for a while.  Dilute it with some water and pour over the plants. 

Maravilla Lettuce

Maravilla Lettuce

The image above shows the final product. These lettuce have been recently transplanted from modules. They will quickly expand and completely cover the soil. No weeds will be able to grow.