The most important rule, when planning a vegetable garden, is to only grow what you will eat!
1. Find the right containers
You can start seeds in almost any type of container, as long as it's at least 2-3 " deep I prefer the convenience trays that are already made for purpose .YOU CAN USE OLD POTS, BUT STERILISE THEM FIRST2. Prepare the "potting soil"
Choose potting soil that's made for growing seedlings i.e John Innes seed and potting compost that is available in the garden pavilion. Do not use soil from your garden or re-use potting soil from your houseplants. Start with a fresh, sterile mix that will ensure healthy, disease-free seedlings
3. Start planting
Check the seed packet to see how deep you should plant your seeds. Some of the small ones can be sprinkled right on the soil surface. Larger seeds will need to be buried. For insurance, I plant two seeds per cell (or pot). If both seeds germinate, I snip one and let the other grow. It's helpful to make a couple divots in each pot to accommodate the seeds. After you've dropped a seed in each hole, you can go back and cover the seeds.
Moisten the newly planted seeds with a mister or a small watering can. To speed germination, cover the pots with plastic wrap or a plastic dome that fits over the seed-starting tray. This helps keep the seeds moist before they germinate. When you see the first signs of green, remove the cover.
4. Water, feed, repeat
As the seedlings grow, use a mister or a small watering can to keep the soil moist but not soggy. Let the soil dry slightly between watering. Keep seedling area airy to prevent disease
5. Light, light, light!
Seedlings need a lot of light. If you're growing in a window, choose a south-facing exposure. Rotate the pots regularly to keep plants from leaning into the light. I. Keep in mind that seedlings need darkness, too, so they can rest. As the seedlings grow taller, raise the lights.
6. Move seedlings outdoors gradually
It's not a good idea to move your seedlings directly from the protected environment of your home into the garden. You've been looking after these seedlings for weeks, so they need a gradual transition to the great outdoors. The process is called hardening off. About a week before you plan to set the seedlings into the garden, place them in a protected spot outdoors (partly shaded, out of the wind) for a few hours, bringing them in at night. Gradually, over the course of a week or 10 days, expose them to more and more sunshine.
Justin Smith, HorticulturalistPowerscourt Garden Pavilion
2. Prepare the "potting soil"
Choose potting soil that's made for growing seedlings i.e John Innes seed and potting compost that is available in the garden pavilion. Do not use soil from your garden or re-use potting soil from your houseplants. Start with a fresh, sterile mix that will ensure healthy, disease-free seedlings
3. Start planting
Check the seed packet to see how deep you should plant your seeds. Some of the small ones can be sprinkled right on the soil surface. Larger seeds will need to be buried. For insurance, I plant two seeds per cell (or pot). If both seeds germinate, I snip one and let the other grow. It's helpful to make a couple divots in each pot to accommodate the seeds. After you've dropped a seed in each hole, you can go back and cover the seeds.
Moisten the newly planted seeds with a mister or a small watering can. To speed germination, cover the pots with plastic wrap or a plastic dome that fits over the seed-starting tray. This helps keep the seeds moist before they germinate. When you see the first signs of green, remove the cover.
4. Water, feed, repeat
As the seedlings grow, use a mister or a small watering can to keep the soil moist but not soggy. Let the soil dry slightly between watering. Keep seedling area airy to prevent disease
5. Light, light, light!
Seedlings need a lot of light. If you're growing in a window, choose a south-facing exposure. Rotate the pots regularly to keep plants from leaning into the light. I. Keep in mind that seedlings need darkness, too, so they can rest. As the seedlings grow taller, raise the lights.
6. Move seedlings outdoors gradually
It's not a good idea to move your seedlings directly from the protected environment of your home into the garden. You've been looking after these seedlings for weeks, so they need a gradual transition to the great outdoors. The process is called hardening off. About a week before you plan to set the seedlings into the garden, place them in a protected spot outdoors (partly shaded, out of the wind) for a few hours, bringing them in at night. Gradually, over the course of a week or 10 days, expose them to more and more sunshine.
Justin Smith, Horticulturalist
Powerscourt Garden Pavilion 
