Seedling Success - My top 12 tips
I have been growing from seed for 20+years now and have made many mistakes along the way. When do you start to sow seeds, what conditions do they need and what are the pitfalls?
Let's start by saying that nothing is for sure, but given the right conditions seeds will grow. It’s very easy to get it wrong with watering, temperature and pests but it’s the cheapest way to fill a garden and will give you many blooms which are not commercially available in the garden centres. You can also ready my Beginners Guide to Growing from Seed - The Dark art of Propagation to start off with.
I start most of my seeds in my greenhouse at home as they need to be checked on daily and watered regularly. If for some reason I can not get down to my plot one day they will dry out in the heat and die. Some can be sowed direct into the ground but I do find that by planting out sideable plants that they are much more able to withstand pests and diseases and of course the weather. There are some seedlings which do not like being disturbed though so it is best to sow those direct such as poppies.
So with seed sowing season upon us I have compiled my top 12 tips for successful seed sowing:
1. Do not start sowing seeds too early. It’s very easy to get carried away and sow lots of seeds too early, especially if you have a greenhouse but even if they do grow well at first you will have nowhere to transplant them as it will be too cold outside. Follow the instructions on the seed packet which will often say to sow 10-12 weeks or 6 weeks etc. before the first frosts. Seeds sown later will fair better with increased light levels and will often grow stronger and faster than those sowed too early and often catch them up. I often find that many of my seedlings sowed just 2 weeks apart flower at the same time.
2. Moisten your compost as if you water onto a dry mix you will find that your seeds can easily get washed to the sides of the pot. Just a small drizzle of water is enough. It does not need to be soaked through at this stage.
3. Tamp down the soil inside your pots so that it is compact. Roots dont like large air pockets and will not grow well through them, also It will be much easier to push out the seedling for potting on.
4. Don’t sow seedling too thickly as this will just lead to disease and the seeds will have too much competition to grow strongly. Better to sow as thinly as you can so the roots have plenty of room to grow. This will also make pricking our easier as the roots will not be so much of a tangled mess
5. Use vermiculite to cover seeds rather than soil. Soil can form a hard crust on the top of the soil, especially if the seeds are taking a long time to germinate – some can take as long as 3-6 moths !
6. Use a heated mat to propagate seeds. It’s amazing how much quicker they will germinate.
7. Always label your seed trays with the variety and date sowed. It can sometimes feel like a long time while waiting for germination but in reality only 2 weeks has passed – which is perfectly normal. It’s also good to test your marker pen to ensure that it is permanent, I have used one in previous years and later found that it was not quite to permanent as the label said it was! If in any doubt then a pencil will work well and will not wash off.
8. If you have used a cover on your pots or trays then take this off as soon as the seedlings have germinated as the high humidity will kill them off.
9. Water seedlings from the bottom as much as you can. This will prevent any problems with disease and fungus growing on the surface of the soil and killing your seedlings.
10. Take care with watering and feel the soil by popping your finger into the soil to check if they need water. Don’t let them dry out and don’t over water them. Easier said than done I know. Don’t assume that they will all need the same amount of water either. You many need to water some every day and others only every few days.
11. Ensure that you harden off plants well before moving them. It is very tempting to just move then from the cosy warmth indoors to get your space back and sow more seedlings but the shock of the wind & rain may kill them. If you can make a cold frame this is the best way to introduce them to the outside world as you can just prop the lid open little by little each day and get them slowly used to outside conditions. Then once you have done this over the course of about 1 week you could take them out of the cold frame during warm days and pop them back in at night before finally leaving them outside after around 2 weeks.
12. Ensure that you prick out seedlings at the right time. Do not prick them out too early, wait until they have developed their first set of true leaves and ensure that you handle them by their leaves not the stalk. Also do not leave them to get pot bound as they will end up a messy tangle as you will not be able to separate them easily, damaging the roots in the process. Remember that the seed sowing compost you used when sowing will only hold enough nutrients for the first few weeks if the seedlings life –up to around 6 weeks so it is important to prick them out and pot them on after a few weeks into a John Innes number 2 or general mix potting compost.