As well as being the web administrator for Ardcarne Garden Centre I am also a keen gardener with a particular interest in growing my own fruit and vegetables.
To get off to a good start, I tend to begin propagating seeds very early in the year and you don't need a heated greenhouse to do it. Right now I have seedlings growing indoors using a variety of propagation aids, including a couple of small heat mats, an unheated and an electric windowsill propagator and some home made efforts – mainly using those plastic trays that supermarkets package mushrooms in, combined with some saved cardboard toilet roll innards.
If you take a look at the photo attached, taken in the third week of Jan, to the left I have some seeds yet to germinate in modular trays, that are sitting within another tray on a heat mat. In an electric windowsill propagator I have some cauliflower and oriental salad leaves growing and a couple of the trays have tomatoes under cover that have germinated. There is also a tray of lettuce seeds to the bottom right, admittedly containing some casualties, and then in the centre I have some healthy broad bean seedlings working away with more to come.
All of these were started off in the first week of January and the best of the lettuce, cauliflower and tomato seedlings have already been potted on. Despite being pretty leggy seedlings originally, they are now looking healthy, as with most plants, you can simply re-pot them up to the point where the leaves are forming, carefully burying that leggy stem. This is true of most brassicas (plants from the cabbage family) and is encouraged for tomato plants, as the stems on tomatoes will develop fine hairs that will develop into roots once submerged in the soil. The key is to handle them by the leaves when potting on, don't crush the stems, and make sure you don't overwater them in order to prevent any stem-rot. The tomatoes will also still require that extra heat from a heat mat until they can be transferred to a green house, conservatory, sunny windowsill or even a grow-house later in the year.
The broad-beans have now all germinated and are a tough plant that will be quite happy growing away in those home made trays I referred to, until I come to transplant them outside. These could also be started off in root trainers, which are perfect for beans and sweet-peas, can be re-used every year and enable you to see exactly when the roots are fully developed for potting on or planting out. Sweet-peas are certainly a plant that can be started off as early as January and don't even require heat.
Now, I may have started earlier than most professional gardeners would recommend, but as we come through February into March, there's certainly opportunities to get more seedlings started. If you are looking to grow tomatoes and peppers, for most varieties it is essential in our climate to have them propagating by the end of March at the latest, to ensure you have something to harvest in late summer/autumn.
For a more qualified approach to growing however, I would highly recommend the books “Vegetables for the Irish Gardener”, and “Vegetables for the Polytunnel and Greenhouse” by Klaus Laitenberger as they are tailored for growing in our climate.
I would like to add though, don't be afraid to engage in a bit of trial and error. Most seed packets will contain more seeds than you will probably be able to use or need before their expiry date. You can usually afford a few casualties, at no great expense, and probably still have enough survivors to grow on and keep you going.
Ardcarne Garden Centre has a range of propagation accessories now in stock, a huge variety of vegetable and flower seeds and a pool of staff, far more qualified than me, that will only be too happy to help with any questions you may have.
Take care and happy growing!