It has taken me a while to get the hang of carrots. Considering that they are one of our native species and that they grow wild almost anywhere that is a bit embarrassing. However, in gardening we learn by our mistakes. Over the years I’ve found ways of growing quite respectable carrots on the rooftop.
Even though carrots are cheap to buy in the supermarket, the smell and flavour of an early variety taken straight from soil to plate is irresistible. And now that they are cites as having so many health benefits, they seem a must for the rooftopvegplot. In other words, a bit of care with the soil preparation and sewing will repay dividends later in the year.
The recent introduction of new varieties mean that carrots can be cropped almost all year round. They are a cool season crop, enjoying the shadier autumnal world that the heat of summer, so on the roof top – where it can get a bit Mediterranean in summer - I think the autumn planting is preferable. (Though a few square feet of spring carrots add deliciously to the first summer salads.)
Carrots, even the small round ones have long taproots, and these like turnips and other roots crops mean that only very average results can be achieved in my shallow raised beds. I have found far more benefit from growing carrots in deep pots, the same pots that I use in summer for potatoes. These are about 400mm across and 450mm deep.
Carrots require a nutritious, well drained and sandy soil. They don’t like newly manured ground and they don’t like stones. So soil preparation is important. It is better to provide the seedlings with a slightly impoverished soil and then feed regularly with a seaweed wash or a liquid tea. Niki Jabbour swears by a little wood ash sprinkled in the planting trough. This she advises will bring the acidity up a bit, and they like a slightly acid soil.
There are a worrying diversity of carrot varieties. Frankly, for spring sewing just about anything will do, as long as you have deep enough pots. The competition growers grow carrots in deep oil drums filled almost completely with sand. But for us mortals, on a smaller scale, the early varieties and the miniature types do well. All of the varieties below can be planted in a cold frame or hoop tunnel 8-12 weeks before the first frosts. For London that gives a last reliable planting date of early October, but in a good year you can risk planting up until November in a sheltered and sunny spot.
I found this very good diagram of carrot shapes, which is helpful when choosing your variety. I find that the images in the seed catalogues are not always helpful. THey are never to scale so the Imperator looks just like the Amsterdam! Carrots don’t mind too much about low light levels, so they do not suffer too much at the ten hour cut-off date, October 25th in London. But the seed must be fresh. THis is one occasion when last years seed packet won't do.
- Nantes is a small early and fast maturing carrot. As it is a stalwart in the carrot world, I can also find it sold on seed tapes or as pelleted seeds (both useful for the heavy handed broadcaster – see below)
- Mignon (12 weeks) is fast growing and recommended as a baby carrot.
- Mokum F1 hybrid, a larger variety that is supposed to like snuggling with its cousins in a deep pot.
- Parmex – the favourite of Nikki Jabbour, these are small and round, and will, according to the catalogues, even crop in a window box. (I’ll have to try that)
- Purple Haze are frighteningly bright purple. They are bigger than the other recommended varieties so consequently need a deeper pot.
- Chantenay, are and old variety of short, fat and stubby carrots, so excellent for shallower ground. Thompson and Morgan do a cultivar called Supreme.
Sowing carrot seed requires some care. If the seed is old, they will not germinate. If they are planted too close, they will not come up. If the soil is too wet and sticky, they will not come up. If they get too much sun and dry out, they will not come up. If there are weeds in the mix, and you are not vigilant, they will not come up!
Some people suggest sowing radishes with the carrots, this thins the spacing and because the aeration of the soil as the fast growing radishes are plucked, is good for the carrots. Others swear by seed tapes or mats. But good varieties are often difficult to find. Suttons do a seed tape for Nantes and Amsterdam (another early variety) and Bakers do a mixed radish and carrot tape (for spring). I haven’t found a supplier of seed mat for carrots, in traditional gardens they are sewn in rows. But I have tried making my own with kitchen paper and flour and water glue. There is a nice how to guide in Annies Kitchen Garden Blogspot
It is also important to keep the seeds shaded until they come up. I place a newspaper mat over the top until they’ve come through. However I havent found the technique to be foolproffo.
My experiment with Kale seeds produced less than perfect germination. I wondered whether the slugs had feasted on the glue. I dididnt leave the sheet to dry before planting - any thoughts readers?
if all this detailed sewing instructions has put you off carrots, the good news is that from now on it is plain sailing. Feed occasionally, make sure the automatic watering is working and weed out any rogue that seeks to crowd out the crop. As long as the pots don’t dry out they should be fine. The foliage looks lovely and does the work of shading for the plant, so there is no need to find too shady a spot, even in high summer.
Carrots keep for ages in the soil, so there isn’t much point in succession sewing. Start cropping intermittently, as soon as they are large enough to eat, leaving the in between plants to grow larger as they are given more soil-space.
Carrot root fly should not be a problem on a roof top garden, the critters don’t fly high. But to be on the safe side from late spring to later summer they can be shaded with Enviromesh, or a fleece.