Days are finally starting to get a little lighter in late March, which makes all the difference – it's now time to sow the seeds you prepped so carefully last month.

Planning

You can start to think about other things you'd like to grow. Most vegetable and some herbs are classed as hardy annuals – they germinate, flower, fruit and set seed all in one year. The 'hardy' bit means that they can cope with a bit of cold weather, but do watch out though for very cold nights and protect them with horticultural fleece

Now is the time to sow herbs such as coriander, dill, fennel, oregano and parsley, straight into containers outside. For an endless supply of fresh salad, you will need to continue to sow spring onions, mixed salad leaves, radish and even beetroot every three to four weeks until mid-September, which will ensure plenty of fresh pickings all the way through the summer.

It's also a good time to plant up a herb container with any other herbs you can buy in pots, such as rosemary, thyme, mint and sage. For those of you with a bit more space you might like to plant some shallot or onion sets. If you love garlic, now is the last chance to get that planted for a harvest this year. I love using the young shoots – they're delicious pan fried with prawns.

Sowing

Fill your container with seed compost. Firm the soil lightly and sow the seeds thinly; spread them evenly over the compost and cover – seeds generally need to be covered at about twice their depth. Firm again lightly to make sure the seed is in contact with the soil.

You will notice on the back of seed packets (do read this info – the instructions are helpful for first timers), it will talk about 'pricking out'. This means separating your little seedlings into modules (separate containers in a seed tray so they have room to grow). Transplant carefully holding on to one seed leaf (important), gently prising the seedling from the soil using a dibber – or even a pencil would work in a pinch. Replant, taking care not to damage any part of it, then water.

Upkeep

Do remember to water your seeds/seedlings sparingly, using a very fine rose on your watering can or, preferably, immersing the base of the container in water until the top surface is moist. Many failures are made here; too much water and the seeds either fail to germinate or collapse under the effects of fungal disease; too little and they will dry up, unable to recover and grow.

Hopefully you have already got tomato and chilli seeds underway now, with three seeds to a small pot. Make sure you keep them inside until the last of the frosts – mid-May usually – then they can go outside. You will probably need to repot them in a slightly larger pot before they go outside – do this when you see signs of root growth at the base of the pot. Giving them space to develop a good root system will provide you with an endless supply of tomatoes and chillis.

Next time, I'll be giving more info on the 'cut and come again' harvesting techniques, how to grow French beans, plus all the other veg best left to sow until the end of April beginning of May.

Amanda Brame is Deputy Head of Horticulture at Petersham Nurseries, Church Lane, Petersham Road, Richmond TW10 7AB; petershamnurseries.com