Hardening off seedlings

Since Beltane, all my seedlings have exponentially shot up in their seed trays and pots. This is due to both the increase in temperature and the daily, incremental changes in the length of daylight. In some cases, this quite literally happens overnight!

A few blog posts ago we discussed ‘potting on’, which is the process of planting a seedling in a bigger pot, once at least one set of true leaves, rather than cotyledon (baby) leaves have developed.  Below is a pic of a pea seedling that we potted on a few days ago. Sown 7th April, it was a slow start this year for this first batch of  peas, and a poor germination rate also, with perhaps only 7 out of 40 germinating. The next batch look like they are faring slightly better. I’ve also ordered dried peas from the supermarket which Trellis recommended as a stand-in for horti variety peas! Within the last week, thankfully the peas have shot up, and started to develop the mighty root system required to anchor them in the ground whilst they reach for the sky.

As above, so below: pea seedling

We potted on peas, chard, kale, pak choi, which I’m growing for seed later in the year, and a few spinach. You can see the crowded seed tray and my glam assistant potting on in the slide show below. Most of the seedlings will  be made into bundles to distribute in a few weeks time around the therapy gardens, which are still in lockdown too; the rest will stay in our garden.

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We have only been able to grow as many seedlings as indoor space in the house has allowed, as I don’t have a greenhouse in the garden anymore. I’ve also used plastic storage boxes as DIY cold-frames (mini greenhouses) to extend capacity outside. Other constraints you might be facing during this time are access to compost, seeds or pots/seed trays. Fortunately I had a stash of all three before lock-down, belonging to myself rather than the project! It will be a lovely parting gift to the therapy gardens (my contract finishes early July) to provide a happy, healthy group of wee starter seedlings for the 2020 growing season.

The weather has been absolutely glorious and it can be so utterly tempting to plant out seedlings in the garden already. Every year it is the same…the seedlings are champing at the bit to get out the constraints of their trays or pots and into the soil, the high-maintenance routines of watering, protecting, turning seedlings inside is wearing thin, and it just seems like it’s time to get the wee darlings outside into the big beautiful world and settled into their forever home.

courgette seedlings rapidly outgrowing their ‘potted on’ pots. May need to repot up a pot size

However, the forecast last night was for a cold spell towards the weekend, with a risk of ‘wintry weather’. Seems to have changed again this morning, but it’s always good to be cautious with your precious little ones. Depending where you are in the world, the risk of last frosts is worth knowing. In UK this website gives the date range by place . For where we live it gives mid May. But I would prefer to err on the side of cautious and take this date with a pinch of salt. I’ve seen snow in June before!

so many seedlings!!!

I have two main batches of seedlings on the go at present, those sown in the second week of April, and those sown a few weeks later. Those sown early April are in the process of being hardened off.

Stage One:

These seedlings now spent their days outside in the sunshine,  in the storage boxes with the lids off. This is the first step into acclimatising them to the temperature outside of the controlled environment of warm house windowsills. I put them out around 10ish, or once there is a wee bit of heat in the air, and then I bring them back inside again in the early evening before it cools too much.  This is after a thorough check for any hitch hiking slugs and snails that may be lurking under the seed trays of course. They are such sly wee buggers; a baby slug escaped my beady eye the other day and  ate half a massive courgette leaf through the night a few days ago! I daresay my neighbours think I am ‘eccentric’, as they watch my morning and evening green gym ritual of moving hundreds of plants around; I will continue this horticultural hokey cokey for the next week or so and then , weather dependent, move onto stage two.

Stage two:

In this stage I will leave the seedlings outside in their storage boxes. For the first few nights I’ll leave them out overnight with the lid on, and then for the next few nights with the lids off.  Please note this is all very weather and seedling dependent, hardier seedlings such as brassicas and peas will harder off MUCH quicker and safer than the more tender watery stems of the courgettes. In the final stage I may leave them out for a few nights outside of the protection of the boxes, but probably not, as the slugs would have a field day. At this stage I would rather just get them planted out into their final positions and use slug castles to protect them. And have horti fleece at the ready to throw on top if the weather suddenly changes.

This is all with the exception of the 41 sunflower seedlings on the go at present as I simply do not have the space to keep them inside! During the day they sit in their boxes outside with the lids off (they are too tall for the lids now!  And in the evenings they overnight in my car, which I’ve repurposed as a DIY greenhouse during lockdown…

The second batch of seedlings on the go are far too young to do anything other than stay inside. They will however grow more quickly than the first batch and should be ready to begin hardening off the 3rd or 4th week in May. This will mean my storage boxes will be emptied of the first batch and ready for the next. Gardening is very much about forward planning and resources. Get it right and it is a smooth conveyer belt from seed packet to garden, get it wrong and Spring can be a stressful jumble of chaos!



Published by theplothickens

passionate about permaculture, interested in sharing my experiences of designing my allotment using permaculture principles

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