Our top tips for transplanting seedlings

transplanting Lupin Seedlings

Our top tips for transplanting seedlings

So, the weather’s warming up and your greenhouse seedlings are almost ready to go out into the big wide world. But how do you know when the time is right and what can you do to give them the best chance of thriving in their new home? Here are a few tips on transplanting seedlings successfully.

Check your garden planner: your seedlings need to go out at the right time, but keeping track of what needs to be planted and when can get confusing if you don’t have a plan. If you need a bit of guidance, the RHS Veg Planner might come in handy.

Assess your seedlings: there’s no set rule here, but a good way to check whether your seedlings are ready for the outdoors is by leaf growth. If your seedlings have around 4 ‘true’ leaves (as opposed to the initial seed leaves) they should be far along enough to be planted outside.

Get your soil ready: whether you’re transplanting seedlings into patio pots, raised beds or a ground level vegetable patch, you need to make sure the soil is right for whatever you’re planting. Nicely aerated, well-fed soil or compost that’s the right pH for the particular crops you’re growing should give them the best start. Many gardeners also swear by adding a dash of phosphorus rich fertiliser to planting holes to give seedlings an extra boost.

Acclimatise your plants: after the cosiness of the greenhouse, your seedlings might not appreciate a sudden change of environment. You’ll need to get them used to the outside world gradually before planting out. Leaving trays outdoors in a sheltered spot for a few hours a day about a week to a fortnight before transplanting should help them toughen up enough to survive the transition. If in doubt you can pot the seedlings on and keep them lower down in your mini greenhouse until the weather improves.

Parsley patiently waiting for better weather

Watch the weather: if you’re still experiencing harsh frosts or the forecasts are particularly unfavourable, you might want to hold off on planting out or find another way of protecting your plants after transplanting. On the days that you do plant out, earlier in the day in calm, mild, overcast weather is preferable. It’ll help stop your seedlings being exposed to too much heat, rain or wind while they settle in.

Dig the right hole: different varieties need to be planted at different depths, so it’s a good idea to double check the required measurements for each plant type before you start digging any holes. If you’re not sure, a good rule of thumb is keeping the new soil level the same as the current soil level of the seedling. It’s also helpful to make the transplanting hole about twice the width of the root ball, so you’ve got plenty of room to work with.

Be gentle: damage to those delicate root systems could spell disaster, so gently does it. A soft squeeze of the pot should be enough to tease the seedling and compost out in one. 

Water them in: watering your seedlings well both before and after transplanting will help keep the roots hydrated and happy. It’s best to get them straight from pot to hole, so that the roots don’t get dry. If you’re worried about the soil drying out after planting, you could always add a layer of mulch.

Every gardener has different tricks up their sleeve. Through experience (and sometimes pot luck) you’ll find your own groove when it comes to transplanting seedlings. However, if you’re new to the process, the above tips might just help you avoid some of the common pitfalls. Once your spring seedlings are in, you’ll have plenty of lovely veg to look forward to over the coming months.

We love this time of year, so we’ve got loads seedlings on the go here at Harvst HQ. If you’d like to know more about how a Harvster mini greenhouse can help you nurture seedlings for the garden or grow crops for the entire life cycle, get in touch.