Thinning Seedlings Might Feel Wrong, But It’s the Secret to Bigger Harvests – And Now Is an Ideal Time to Do It
Give your seedlings space for the strongest to survive and thrive
I have always enjoyed growing vegetables from seeds. Sowing and nurturing them through to harvest is very satisfying. Along the way, thinning seedlings is essential to give your plants a chance of reaching full size.
We’ve all been guilty of sowing too thickly. But even if you follow the guidelines on packets, they’ll often recommend sowing thinly then thinning to the final spacing. Without thinning seedlings, you get tightly-packed plants battling for light, water and nutrients. For the best crop, you need to thin these seedlings and allow the strongest to develop.
You can try to be precise when you sow seeds outdoors, but thinning seedlings is often unavoidable. It pays to sow seeds closer together than the perfect spacing, as you cannot guarantee they all germinate. It is better to sow a bit thicker and thin as required.
This heirloom vegetable seed kit from Amazon provides seeds for 32 different crop varieties, making it ideal if you are looking for seeds to sow to fill your vegetable garden.
What Does Thinning Seedlings Mean
Thinning seedlings means thoughtfully removing some of them to give the remaining ones more room to mature.
It is required if you sow too many seeds and the result is overcrowding, as seeds don’t form an orderly queue and germinate exactly where you want them. They bunch up, sometimes germinate on top of one another, and they don’t mind jostling for position.
Seedlings growing bunched together do not make a healthy, productive kitchen garden. If left to battle, they will all compete for sunlight, water, and nutrients. They fight for the resources they need, but in the end they all fail to get what they want. Overcrowding leads to unhealthy, stunted vegetables and disappointing harvests
Thinning seedlings involves picking the smallest ones and removing them from the fold. It gives more room to the stronger ones, ensuring they can get all the water and nutrients they need and have the space to reach maturity.
You could try sowing at the ideal spacings to avoid thinning seedlings, but that comes with big risks. Whether you are sowing in rows outdoors or into pots indoors, planting a few extra seeds is the best course of action. You cannot guarantee 100% germination and that they all come through life unscathed; the weather and pests can take their toll.
It is better to sow a few seeds per pot, or sow extra seeds along the row, and then thin seedlings. Any seedlings that are weak or have been affected by pests can be removed, leaving the strongest ones.
When to Start Thinning Seedlings
The time to start thinning seedlings is once they have developed their first set of ‘true’ leaves. All seedlings have a first set of embryonic leaves called cotyledons. The second set of leaves will be the first ‘true’ leaves, and these look like smaller versions of their adult foliage.
Once the seedlings have developed these leaves, you know what they are. And by this stage you can start to see which are the healthiest and which are struggling a bit more. This is the time to start thinning seedlings.
Don’t fall into the thinking that thinning seedlings is a once-and-done thing. You don’t have to do all the thinning in one go. If you know the spacing for the final plants, you can thin seedlings a couple of times to achieve that. It allows you to get rid of the weakest first, then monitor the remaining and thin them a bit later once you see which are the strongest.
How to Thin Seedlings
Before you start thinning seedlings, check your seed packets to discover the recommended spacings for the crop. Different vegetables have different spacings, ranging from a few inches to feet, so it pays to know what you are working with.
I’ll openly admit that I don’t always adhere to the usual best practice when thinning seedlings.
Let’s start with what most practical advice and guidebooks will say. You should use a pair of sharp scissors or pruning snips (you can get pruning snips on Amazon) to thin seedlings.
Using pruning tools and cutting the stem as close to the soil level as possible ensures you remove the seedling without damaging any around them. This is a very sensible approach to remember.
Many times I have thinned seedlings by pulling them, rather than cutting them. However, I only do this with very small seedlings, those that have only recently developed their first ‘true’ leaves.
If you pull them once they are larger and have extra leaves, they’ll also have larger roots. These can be entangled in the roots of seedlings on either side. Pulling them risks damaging their neighbors' roots.
I say you can carefully pull smaller seedlings, but for larger ones, always cut. This ensures you separate seedlings without damaging them.
When deciding which seedlings to thin, remove the smallest or any showing signs of pest or disease damage. Any removed seedlings can be added to your compost, but don’t chuck them all away. Seedlings of lettuce, spinach, beets, radishes, and more can be eaten and added to summer salads.
What to Shop
A pair of pruning snips with thin, pointed blades made from carbon steel. They are ideal for precise pruning tasks, like thinning seedlings at ground level.
A lightweight pair of garden scissors with ultra-sharp, serrated steel blades and a comfortable grip. They can be used for cutting flowers or thinning seedlings.
A pair of snips with long-reach 190mm chromium blades to precisely thin seedlings without damaging others.
A nice way to try and create even spacing is to make a DIY seed tape. You can buy seed tape with pre-spaced seeds, or make your own with some seeds, cornstarch, and biodegradable paper. Attach the seeds to the paper at set spacings using cornstarch paste, then bury the seed tape in the soil.
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