‘Why are my seedlings leggy?’ – gardening experts provide practical solutions

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Modern vegetable gardening
Fruit trees
A kitchen garden
Whether you’re growing vegetables for the table or to feed your family and friends, a vegetable garden is one of the best ways to enjoy fresh produce without having to leave your home. It’s also good for your health and wellbeing as you can grow things organically and be sure that they’re as natural as possible.

Q: I have started growing annuals indoors from seed, ready for planting out when the frosts finish. They’re growing on my kitchen window sill, and germinated well, but now the seedlings are looking weak and leggy. What has caused this, and can they be saved?

A: One common reason behind leggy seedlings is insufficient light. On window sills, this is usually because the light is only coming from one direction. ‘Plants grow towards light (a process that’s known as phototropism) and if this only comes from one side then leggy, stretched seedlings result,’ explains Lucy Chamberlain, a gardening expert.

starting seeds indoors, they should be sown shallowly in proprietary seed compost at a temperature of around 64˚F, he says. ‘If the temperature is higher, they grow so rapidly that they quickly become exhausted and collapse.’

John Negus

RHS Step by Step Veg Patch, available from Amazon (opens in new tab), which covers 50 types of fruit and veg.

How to save leggy seedlings

In some cases, it’s easiest to cut your losses and start again by sowing fresh seeds. However, if you want to try and rescue your leggy seedlings, you can try pinching them back. This can encourage bushier growth, depending on what type of plant it is.

Using clean scissors or your forefinger and thumb, shorten the shoots, leaving at least two pairs of leaves from the base. Then, place the trays or pots somewhere cooler in good light (you can follow the tips below for extra chance of success). Ensure you thin them out when needed, too.

When it’s time to transplant them into larger pots, some plants, including tomatoes, can be planted slightly deeper into the soil, up to the first leaves.

3 ways to prevent leggy seedlings

Whether you’ve tried to save your seedlings or have started a new batch, follow these tips to prevent the problem from happening again.

1. Move your seedlings to somewhere more suitable

Positioning is key for preventing leggy seedlings, so ensure you get this right for the best results. You want somewhere with plenty of bright, indirect light so that they can grow strong.

‘Bay windows, porches, conservatories or greenhouses offer the best results,’ says Lucy. However, ensure your greenhouse is clean: ‘Dirty glass can block out anything from 30-50% of the sunlight hitting it.’

2. Turn the seedlings

If possible, give each pot a half-turn (180˚) every day, suggests Tim Rumball, a gardens writer. This will draw the seedlings in the opposite direction every 24 hours, he explains, ultimately resulting in upright growth.

3. Make a reflector box

If you don’t have a spot with perfect lighting conditions or the time to turn your seedlings daily, you can still avoid the seed sowing mistake of not providing enough light by making a simple reflector box. Tim Rumball explains how to do it:

Alternatively, Lucy suggests simply placing a length of white card behind your window sill plants to reflect the light.