Q&A: What Seeds Should You Start in March?

March is when the gardening engine starts humming. Light levels rise, soil begins to wake up, and seed packets start whispering from drawers. If you’re wondering what to sow and how to do it properly, this guide answers the most common questions.

 

 

Why is March a good time to start seeds?

March gives you a head start. Sowing now means:
• Stronger plants by planting-out time
• Earlier harvests and longer flowering periods
• Better use of the growing season

It’s the sweet spot between winter dormancy and spring growth.

What vegetables can I sow in March?

You can start a surprising amount:

Indoors or in a greenhouse
• Tomatoes
• Chillies and peppers
• Aubergines
• Cucumbers (late March)
• Courgettes (late March)

Direct outdoors (if soil is workable)
• Carrots
• Beetroot
• Spinach
• Lettuce
• Radish
• Peas
• Broad beans

Cool soil crops thrive now, while heat lovers prefer indoor warmth.

What flowers should I start in March?

For summer colour, sow:

Indoors
• Cosmos
• Zinnias
• Marigolds
• Nicotiana
• Tithonia

Direct outside
• Sweet peas
• Nigella
• Calendula
• Cornflowers

These will give you blooms from early summer onwards.

Do I need to start seeds indoors?

For tender plants like tomatoes and peppers, yes. They need warmth and protection.
Hardy seeds like peas, beans, and some flowers can go straight outside once the soil isn’t frozen or waterlogged.

A sunny windowsill works perfectly if you don’t have a greenhouse.

What temperature do seeds need?

Most seeds germinate best between 18–22°C.
A warm room, propagator, or heated mat helps speed things up, especially for chillies and peppers.

How much should I water seedlings?

Keep compost moist, not soggy.
Too much water causes rot. Too little stops germination.
Water from the bottom when possible to avoid disturbing tiny seedlings.

Do seedlings need light?

Yes. As soon as they sprout, they need plenty of light or they become leggy and weak.
A bright windowsill or greenhouse is ideal.

Turn trays regularly so they grow straight.

When can I move seedlings outside?

Only after hardening off.
This means gradually introducing them to outdoor conditions over 7 to 10 days. Start with a few hours a day in a sheltered spot.

What compost should I use?

Use seed compost, not multi-purpose.
Seed compost is finer and lower in nutrients, which helps roots develop properly without burning young plants.

When should I prick out seedlings?

Once they have two true leaves, gently move them into individual pots.
Handle by the leaves, not the stem, to avoid damage.

What are the biggest beginner mistakes?

• Overwatering
• Starting too early with no light
• Using the wrong compost
• Not labelling trays (everything looks the same at first!)

Start small and stagger your sowing every 2 to 3 weeks.
This gives you continuous crops and flowers instead of everything maturing at once.

March is not about doing everything. It’s about starting something.