The trick with growing celery is to take a lot of care sowing your transplants, making sure the plants never get stressed or pot bound. When planted out remember celery is originally a wetland plant so make sure the soil around it is kept moist otherwise you'll end up with stringy and bitter stems.
Sowing Celery Seeds
Celery needs to be sown under cover in March. The seedlings are then planted out after the the last frosts in late May / early June. The young plants are started off early and spend a relatively long time indoors so we've a little bit of work as to how to get them going.
Broadcast sow (Sprinkle) the seeds over a seed tray or pot containing a fine seed compost. Don't cover the seeds as they need light to germinate. You need to place the pot or tray in a warm place, a south facing windowsill is ideal or in a propagator if you have one.
Celeriac may take 2 or 3 weeks to germinate so don't worry id they seem to be taking a bit long! Keep the compost moist and don't let it dry out.
You will need to prick the seedlings out into modular trays about 2 weeks after germination.
Fill your modular tray with compost and make a hole in the cells you want to plant about the size of the seedling rootball. To do this you need a learn a little trick which is to gently loosen the roots beneath the seedling with a suitable stick. (We used a pen) and lift it gently by the leaves.
Place the seedling root in the modular tray and carefully fill the compost in around the root. Plant 1 seedling per tray.
We have used lettuce seedlings in the photos but the principle in this how to grow celery info is the same. It is important the seedlings are pricked out at and early stage to avoid root disturbance which can lead to bolting later on.
Celery plants should be moved to the garden when about 10cm tall and hardened off before planting in their final positions. Plants that have been raised indoors will need to get used to the outdoor temperature and conditions before they can be planted outside, this will take about a week to 10 days depending how the weather is.
The best way is to use a cloche or mini greenhouse. You can leave the cloche off the plants on dry frost free days and replace at night. Gradually increase the time with the cloche removed until the end of the week when you leave it off day and night. If the weather is mild you may not need the cloche, just move the plants outside for longer periods each day.
If you have started your seeds on a windowsill you will need to leave them in an unheated room for a day or two before moving outside to the cloche.
Celery should be planted out at a spacing of 30cm between plants and 30cm between rows.
Water your plants well an hour before planting.
To plant your seedling make a hole in the soil the approximate size of the seedling 'plug'. You need to push the soil in to around the roots firmly with your fingers to get good contact with the soil. Dont firm down on the top of the soil as this can compact it and prevent moisture getting down to the plants roots.
Water the plants after planting but do not soak them. You are better to transplant on a dull day or in the evening to prevent the plants wilting in bright sunshine.
Celery plants should be kept moist at all times, after all they were originally a wetland plant. If celery is allowed to dry out the stalks will get stringy and bitter.
Watering is important in dry weather with more frequent attention much better than occasionally soaking the beds.
Regular hoeing to keep the weeds down is also essential but be careful of the shallow root system when doing so.
The best stems are usually found just after the canopy has closed over (if you're growing in close together).
Harvest the whole celery plant by gently forking it out of the ground. I wouldn't get greedy with the size as large stalks can be stringy.
A trick to keep celery for longer is to harvest early in the morning, trim the leaves off and store in a plastic bag in the fridge. It should keep for 2 weeks or so.