Spinach is fairly easy to grow in the UK climate. As it likes plenty of water and cool conditions, it’s ideal for the typical British summer. There are basically two main types – those with round or smooth seeds, and those with prickly seeds.
The kind you would generally find in a supermarket is the round-seeded. This annual is more delicate and a little harder to grow at home. The main drawback is that it’s prone to bolting (going to seed too early), so make sure it’s well watered and doesn’t get too much sun.
The prickly-seeded type is a biennial, closely related to chard. It tolerates a wider range of conditions, such as drier soil, more sun, or colder temperatures. It will even over-winter if protected from frost. The seeds tend to come in clusters, producing 3-4 plants.
Perpetual spinach is a common variety of the prickly-seeded type. Also known as ‘spinach beet’, technically it’s a chard rather than a spinach. The leaves and stems are slightly tougher than regular spinach, but it’s significantly easier to grow. As well as not quite being a spinach, it’s not quite perpetual either 🙂 but as long as you do all you can to prevent bolting, you can keep cutting throughout spring and summer, and it will keep growing back in abundance.
Round-seeded varieties tend to be lower in oxalic acid – a type of antinutrient. Studies have been made to identify and cultivate varieties particularly low in oxalates, but this is a complex area (1). Those high in oxalates can also be high in chlorophyll, and possibly other useful nutrients too, so it’s important to consider the complete nutritional value.
Ideally, plant where it will have about half the day in shade, as it doesn’t cope with too much heat.
For a summer crop, spinach can be sown directly into the ground from March onwards, but we sow in pots indoors and then plant the seedlings out towards the end of April. While the ideal germination temperature is 15ºC (59ºF), it will germinate from 10ºC (50ºF). Germination takes about 2 weeks.
If sowing into the ground, thin the seedlings out to a spacing of about 8cm when they’re big enough to handle. Then a few weeks later take every alternate plant out and use as baby leaf in salads. Repeat as the plants continue to grow, until the spacing is about 25-30cm. Some recommend 15cm, but the plants can get quite big, and will benefit from the extra space. The more you crowd them, the more likely they are to bolt.
You may want to plant successionally indoors, later in the season. If you get a hot spell and the mature plants start bolting, it’s useful to have some spares. If you end up with too many, they can always be used at the baby-leaf stage. Keep sowing well into late summer and early autumn to provide winter crops. Growth will slow down considerably from August.
Some say for winter crops, it’s best to plant straight into the ground mid-September, as that makes the plant more resistant to cold. Either way, cloches will extend the growing season.
If you don’t have much open ground for planting, spinach grows well in large containers. If you just want to cut it at the baby-leaf stage, a small trough can also work well – just take extra care to stay on top of the watering.
As with all vegetables, be sure to buy fresh seeds each year to get the best rate of germination.
Spinach likes nitrogen-rich soil, so lots of compost is an advantage. It’s not keen on acid soil, preferring neutral to slightly alkaline conditions.
Grass is rich in nitrogen, so if you have a lawn, an easy way to get some back into the soil is to use grass cuttings. Ideally dry them out in the sun and sprinkle them onto the soil around the plant. In wet weather, you can still use cuttings as a mulch. Make sure you just add a thin layer, or it can go slimy and attract slugs. Obviously if you’re gardening organically, it’s important only to use grass that hasn’t been treated with chemicals such as weed-killers.
We use Vitax Organic Liquid Seaweed when planting out, and as a feed every fortnight at the height of the growing season. It’s rich in potassium, magnesium and trace elements. We’re also experimenting with Emiko EM-1 – a kind of probiotic for the soil. More about that at a later date.
Harvesting can start in June, or a minimum of 6 weeks after germination. Cut the entire stem of each outer leaf, as near to the base as possible. New growth will keep coming from the middle of the plant.
If you like, you can allocate certain plants for baby leaves. Keep cutting the leaves when young and the plant will stay near the ground and give more plentiful new shoots.
Other plants can then be left to mature. Perpetual spinach produces huge umbrella-like leaves of up to 40cm long, which are still lovely and soft when just cooked lightly.
In either case, be sure not to stress the plant by taking too much at a time – you’ll risk it bolting or dying off altogether.
When spinach bolts, the leaves have a spikier shape, and taste somewhat bitter. It’s best to pull up the whole plant and replace it with a spare in that case, as not much can be done to reverse bolting. You can try cutting down the tall shoot down to the level of the main plant, but it’ll probably keep happening, so you may have to give in and harvest it.
Spinach is not generally susceptible to bugs. Aphids and leaf-miners are the most common insect enemies. If you notice tiny meandering trails all over the leaves, leaf-miners have moved in. As they live inside the leaf itself, not much can be done, except cutting the affected leaves away before the problem spreads.
When spinach is left un-netted, you may have trouble with birds, especially sparrows and pigeons. They particularly like younger leaves, but will happily munch on whatever they can reach. You’ll notice little triangular cuts around the edges of leaves. Raised beds with fitted nets are ideal for keeping birds out. You can also experiment with making your own netted tents from canes.
If sowing direct into the ground, watch out for slugs and snails. They love the seedlings, but lose interest as the plants grow. This is another advantage of sowing indoors, then planting out when the plants are bigger.
Downy mildew can be a problem when the weather is cool and damp. This is one reason to make sure you give each plant enough space – so the air can circulate. Some spinach varieties are particularly resistant to mildew.
Got any tips or questions of your own about growing organic spinach? Leave us a comment below, we’d love to hear from you.