Hillingdon Allotment News 16: Growing Parsnips and Carrots

Both of these vegetables can be difficult to grow on clay or stony soils. However by giving them a little of what they want you can grow some decent crops with a little preparation. By their very nature of having a long taproot they require a soil that is of a sandy texture with a good depth, especially with parsnips, and there are two main ways to do this, depending on what you require.

The first method, suitable for parsnips only, is to bore holes in your allotment about 6” apart by 12” deep, and fill with a compost mixture, (see below), this way of growing is suitable if you require large parsnips for show, or for a large family.

The second method, which is just as effective for both vegetables, is to produce a narrow ‘V’ shaped channel which is filled with the same compost. This channel can be made by digging out soil to a spades depth or by inserting the spade into the soil and working it backwards and forwards until a suitable space has been made. I must admit that I find this last way not very effective as the soil conditions have to be just right otherwise the soil either sticks to the spade or falls into the hole if it is too dry! Cutting out a ‘V’ shape is easier and more effective. The mixture that I use to achieve the desired results consists of about a 50/50 mix of potting compost (you could use a peat free substitute) and coarse sand from the builders merchants, or alternatively for small quantities you can buy bags of John Innes No 2 mix which I have also found to give good results but is soil based. Make sure that the compost is settled in the hole and the best way to do this is to water it well in and then top up as necessary, your seeds are then sown into this mixture.

For parsnips germination can be erratic at the best of times and a minimum temperature of 45F (7C) is required for germination to take place and in bad years I have had to sow the seed several times before getting a result. What amazes me on packets of parsnip seeds is the instruction to start sowing in February as it requires a long growing season, anyone who has tried this will tell you that this is a complete waste of time and money outdoors as the soil is too cold and wet for germination to take place. Late March or early April is soon enough to sow seed for larger plants but last year I sowed a row on the 22nd of May which has produced some nice small plants, but I would not generally recommend sowing so late in the year as this is subject to weather conditions. When sowing in bore holes I always sow at least three seeds and only thin these out when they have produced their first true leaves. For rows I tend to sow at intervals of about 2”- 3” and thin out when I can see where the plants are.

Similar temperatures apply to carrots, but these can be sow in succession throughout the spring and summer depending upon the varieties that you choose. There are numerous varieties of both these vegetables with various shapes suitable for different conditions with carrots having both early and late varieties to extend the season, the choice is yours.

The main problems with these vegetables are attacks of carrot fly which affect the roots of both plants. Use fleece to cover the young plants as a barrier to prevent the fly laying its eggs, carrots now have fly resistant varieties which are worth trying. For parsnips, celery fly can be a nuisance as its grub bores into the leaf causing a scar which can easily be seen and dealt with by removing the offending part of the leaf. Canker is also a major problem, especially with early crops and the best way to deal with this, as there are several types, is to buy canker resistant varieties and sow later even if it means smaller roots.

Finally a warning on parsnips: The juice in the leaves can be very caustic causing very nasty burns as I know from first hand experience. If you are working amongst these plants on a hot day keep both arms and legs covered to prevent the sap touching your skin, no shorts and no short sleeves! I admit now that having learnt my lesson I always use gloves when I am near these plants in hot weather it is well worth the precaution.

Despite the problems these vegetables are well worth while growing and make a good addition to the dinner table.

Return to top