Gradually thin out Swiss chard seedlings to a distance of 30 cm for mature plants or 5 cm for young leaves. After transplanting, thin out the seedlings into cells so that there is only one plant per cell.
For planting, harden indoor seedlings over 7 to 10 days. Plant them 30 cm apart in rows 38-45 cm apart for broad leaves, or 5 cm apart in rows 20 cm apart for young leaves.
As for watering, Swiss chard has deep roots and can withstand periods of drought. However, thorough watering every week during the summer will encourage increased leaf production. Potted plants require regular watering. Mulching helps conserve moisture and prevent weeds. Be careful when watering red-stemmed varieties, as they are prone to bolting.
For protection, use barriers and traps for slugs and snails. Birds can damage seedlings, so cover them with netting or horticultural fleece if necessary. For best-quality leaves in winter, use horticultural fleece tunnels to cover the rows.
The broad leaves are ready about 12 weeks after sowing. Start picking them from the outside of each plant by breaking or cutting off the base of each stem. Remove any flowering stems that form to prolong harvesting. Harvest progressively as needed, cutting or breaking off outer stems. Harvest mature plants in one go, cutting stems at the base.