Parsnips are easy to grow members of the cow parsley family. This family includes carrot, dill, fennel and parsley among others. These seeds tend to have a short period of viability, so new packets of seed should be purchased every year. This family also need warm temperatures to germinate and the air temperature has to reach 12C (52F) before germination occurs. Wait for spring to arrive before you sow any of them. However seeds should be acquired now because this vegetable regularly heads the top ten seeds list and it often disappears off the shelves early on.
Wait for April to sow
Parsnips are slow to germinate and you are much more likely to succeed with growing them if you wait until April before sowing the seeds. Ignore the advice on the packets, which usually recommends February sowing. The temperatures then are too cool and this leads to crop failure. I think this 'February sowing' myth has come about because parsnip seeds take a minimum of 30 days before they appear. So seed companies want you to get seedlings up by March - an impossibility in most years.
Site & Soil
Parsnips will enjoy an open sunny site. Deep sandy soils are the best but even well dug heavy clay soils can produce an excellent crop.
The sowing technique
I use a wide four-inch drill and scatter the seeds along: this gives the roots plenty of space to develop without thinning out at the seedling stage. Some people recommend station sowing, ie leaving six-inch gaps between clusters of seeds. I find this doesn’t work as parsnip germination can be patchy, so you often get wide gaps without any roots. Like carrots, parsnips are not suitable for growing in modular trays as the young root will become constricted. Sow your parsnips directly outside in a well prepared seed bed.
1. Choose a still day because parsnip seeds are very light and papery and they can blow away as you handle them
2. Dig the area deeply and then use a line to mark the row before raking out a wide four-inch drill.
3. Water the drill - this will fix the seeds in position.
4. Sow the seeds to a depth of half of an inch and then lightly cover with soil.
5. Protect with chicken wire to prevent cats and birds from scratching the seeds up.
6. If sowing two rows position them a foot apart (30 cm/12 in)
7. Water the seeds in dry weather and keep the drills weed free
8. As soon as they have germinated (2-3 weeks) you can start to thin them out
Not all your parsnip seeds will have germinated which is why we sowed them in a tighter spacing than their final placement. They will need to thinned or your prize parsnips will be no bigger than a pencil.
The spacing determines the size so:
10cm spacing produces small roots,
15cm spacing produces medium sized roots,
20cm spacing gives you large roots to impress your friends, I'd go for 15.
Thinning means removing any excess seedlings to leave them approx at the required spacing. Once your thinning is done you'll have very little to do for the rest of the season except weeding between the plants. Get yourself and oscillating hoe to make weeding a pleasure. Hoeing not only removes the weeds but it also breaks up the surface of the soil and creates a fine texture or 'tilth'. A good tilth lets air and moisture in to the roots of your plants thus increasing their vigour.
Pests and Diseases
Parsnip canker is common and you're likely to get a little bit. It starts on the shoulder of the root usually caused by drought or damage to the crown. You can control it by the following methods:
Carrot root fly
Parsnips don't suffer from root fly as much as carrots so is unlikely to be a problem unless very common in your area. To prevent the root fly reaching the parsnips cover the crop with a micromesh mini tunnel
Hoe regularly to control weeds and to stimulate the growth of the plant. One of the best gardening tools you'll ever buy is the oscillating stirrup hoe. It's a very effective old fashioned tool that really works properly. Hoeing not only removes the weeds but it also breaks up the surface of the soil and creates a fine texture or 'tilth'. A good tilth lets air and moisture in to the soil, microbial activity is increased which then feeds nutrients to the roots of your plants.
Parsnips are ready to harvest from october onwards. It is best to leave them in the ground and harvest them fresh as you need them. In fact parsnips are better if exposed to hard frost as the freezing temperature changes the starch into sugar making them sweeter. This delicious, hardy winter vegetable develops its sweet, nutty flavour when cold temperatures turn the starches in the root to sugar, so traditionally the first parsnips are only lifted after a hard frost. If you do harvest parsnips before a frost, bag them up and keep them in the fridge for two weeks to sweeten the roots.
If you have a wet garden however and your plot can become water logged it's best to dig them up. Store them in boxes of sand in a cool, frost free shed.