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Beginner's Guide to Planting from Seed 

Browse our Oh Sow Simple Seed Range

Introduction to seeds:

There's something magical about growing from seed. One day, you have a tiny seed in your palm, weeks later, you're harvesting tomatoes or cutting armfuls of flowers you grew yourself. Sowing seeds is more affordable than buying plants. It gives you access to hundreds more varieties, while also giving you a garden to cover all seasons.

This guide covers everything you need to know about how to sow seeds, from understanding what makes seeds germinate to transplanting sturdy young plants into your garden. Whether you're sowing your first packet or troubleshooting why seedlings keep flopping over, you're in the right place.

How a Seed Thinks: 3 Things It Needs to Wake Up

Moisture:  When a seed absorbs water, its protective coat softens and splits, triggering germination. The radicle (embryonic root) breaks through first, followed by the hypocotyl (embryonic stem) pushing toward light.

Temperature: Most seeds germinate between 15–25°C. Too cold and they stay dormant; too hot and they 'cook'. Temperature affects both germination rate (how quickly seeds sprout) and seedling vigour (how strong they grow). At our trial grounds, we've learned that patience beats haste: sowing too early in cold soil leads to rotting and damping-off (a fungal infection). Wait until the soil warms up and there is no risk of frost, before direct sowing outdoors.

Light: Some seeds are photoblastic and need light to germinate. These should be surface-sown on your compost, whilst some seeds germinate in darkness and in the soil. Our rule of thumb is to cover seeds twice their depth. Tiny seeds like lettuce and petunias get barely any cover; larger ones like beans or peas go deeper.

The Before You Sow Checklist

Preparation makes all the difference. Get these basics sorted before you sow, and you'll avoid most common pitfalls.

Choose the Right Compost
 

Never use garden soil in containers as it compacts when wet, harbours weed seeds and may contain pests or diseases. Use seed sowing compost or quality multipurpose compost. We recommend peat-free potting medium with fine texture, excellent drainage to prevent waterlogging, and low nutrient levels (seedlings don't need feeding initially).
For outdoor sowing, prepare your seedbed by breaking the soil into a fine, crumbly texture. Rake it level, and if the soil is dry, water the day before sowing.

 

Essential Equipment
•             Seed trays or modules
•             Propagator or clear covers for humidity and warmth
•             Labels so you don’t forget what you sowed
•             Watering can with fine rose
•             Vermiculite for covering seeds

Sowing Techniques

The range of temperatures that seeds prefer for germination varies considerably but if it is too cold they may rot and if it is too hot they may remain dormant. All our seed packets clearly show the recommended time of year to sow and whether they need to be sown indoors/under glass or can be sown outside.

How to Sow Seeds Indoors

Indoor sowing gives you a head start and greater control over conditions. Fill your containers with compost, levelling it just below the rim, then gently firm it without compressing. Water thoroughly and let it drain.
Sow seeds according to the packet instructions: sow 2-3 per module cell, or thinly scatter in trays. Cover lightly with compost or vermiculite, or leave uncovered if the variety needs light. Label everything with the variety name and date so you know which seeds are which.
Place in a propagator or cover with a clear lid at the recommended temperature. Check daily once germination begins, remove the cover to improve air circulation and prevent fungal issues. Move seedlings to a bright spot. A sunny windowsill works, but watch out for leggy growth.

How to Sow Seeds Outdoors

Ideal for crops that dislike root disturbance (carrots, parsnips, peas, beans). Prepare the soil to a fine tilth, make shallow drills, sow seeds thinly, cover gently, and water with a fine rose. Thin seedlings once they have true leaves.

Caring for Seedlings

Pricking Out

Once seedlings have true leaves, transplant them into larger pots to prevent overcrowding. Fill pots with fresh multipurpose compost and make a small hole with a pencil. Water your seedlings first, so they lift more easily.
Use a teaspoon or a plant label to gently lift the seedlings, and always handle them by their leaves, not their stems. Lower each seedling into your new hole, gently firming the compost around the roots. For leggy seedlings like tomatoes, plant up to just below the lowest leaves as they'll develop roots along the buried stem. Water gently and keep out of direct sunlight for a few days.

Common Problems

Seeds won't germinate: This could be due to using old seeds, incorrect temperature, sowing too deeply, or the compost drying out.

Leggy seedlings: This is a result of insufficient light. Move to a brighter spot, use grow lights or try planting deeper when transplanting.

Hardening Off & Planting Out

If you have grown your plants indoors, they will need to be acclimatised to outdoor conditions, a process known as hardening off. Place plants outside during the day in a sheltered spot a week before you plan to plant them, bringing them in at night. Gradually increase exposure for another seven days until they stay out overnight.
We recommend planting on a mild, overcast day. Dig holes slightly larger than the root balls, gently firm them, and water well. Protect from slugs and cover with fleece if at risk of frost.
If this is successful, why not try something called succession sowing? This is when you sow small batches of fast-growing seeds every 2-3 weeks for continuous harvests of salads, radishes, carrots, and beans.

 3 Recipes for Success

The Easy Salad Mix

Lettuce, rocket, radish and spring onions. Sow directly into containers from March. Harvest as cut-and-come-again leaves whilst your radishes are ready in 3-4 weeks.xz

The Bee Friendly Border

Calendula, cornflowers, cosmos, or this mix of pollinator-friendly flowers. These are all hardy annuals and can be sown directly outdoors from March until May. Deadhead these blooms regularly to maintain continuous flowering.

The First Time Tomato

Choose bush varieties like 'Tumbling Tom' (no staking needed). Sow indoors from March until April, prick out, harden off in May, and plant into containers. Feed weekly with tomato fertiliser once flowers appear.

Frequently Asked Questions

How long do seeds keep for?

This varies depending on what seeds you buy. Onion and parsnip seeds lose viability within a year. Tomatoes, beans, and brassicas can last 4-5 years if stored cool and dry. Always check the 'sow by' date on packets.

What's the best way to water seedlings?

Bottom watering is the preferred method for watering your seedlings. Place your pots in a tray of water and let the compost absorb moisture from below. This avoids disturbing delicate seedlings, but you can also use a watering can with a fine rose; be careful not to flatten small seedlings.

How do I know if seedlings are getting enough light?

Healthy seedlings are compact with short, sturdy stems and dark green leaves. If they're stretching towards light with long, pale stems, they need more. If this is happening, move your seedlings closer to a window or invest in a grow light.

Start Your Growing Journey

At Fothergill's, we've spent decades perfecting our seed ranges. Whether you're sowing your first packet or your thousandth, we're here with quality seeds, expert advice, and everything you need to succeed. Browse our complete range, shop propagators and peat-free compost, and join our growing community for seasonal tips and inspiration.

Happy sowing!
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