Sow Swiss chard about 2 weeks before your last frost, 9 inches apart in rows 18 inches apart, and start picking in 50 to 60 days. Harvest the outer leaves only and one sowing crops for months. Good companions are bush beans, onions and cabbage; keep beets and spinach away.
How to harvest Swiss chard
This is the section that makes the crop worth growing, and getting it wrong is what turns a months-long harvest into a single cut.
Take the outer leaves only. Cut or snap each one at the base of its stalk, close to the crown but without cutting into it. Work from the outside in, taking the largest leaves and leaving everything in the centre.
Never cut the crown. The growing point sits in the middle of the plant and produces new leaves continuously from it. Cut the whole plant off at the base, as you would a lettuce, and you have ended the crop — chard does not reliably regrow from a severed crown.
Take no more than about a third of the leaves at once. The plant needs the rest to keep photosynthesising. Picked this way, one spring sowing produces from early summer until frost, and often through a mild winter into the following spring.
Pick the outer leaves even when you do not need them. Old leaves left on the plant go tough, harbour leaf miner and slow new growth.
Swiss chard companion plants
Good neighbours, and why.
Bush beans fix nitrogen and, being low, do not shade a leaf crop that wants light. Onions and other alliums occupy a narrow upright footprint and share none of chard's pests — the classic argument that their scent deters leaf miner is weakly supported, but the absence of shared problems is a real benefit. Cabbage and other brassicas work as neighbours because their pests and chard's do not overlap; a brassica caterpillar has no interest in chard.
Bad neighbours, and why.
Beets. This one is not a matter of opinion: chard and beetroot are the same species, Beta vulgaris, bred for leaf and stalk in one case and swollen root in the other. They share every pest and disease, they compete for an identical root zone, and they cross-pollinate if allowed to flower. Growing them together concentrates leaf miner and leaf spot on both.
Spinach is a close relative with the same leaf miner problem, for the same reason.
The rule here is simple and unusually firm for companion planting: much of that advice is contested, but "do not group a crop with its own close relatives" is about pest pressure and rotation, and it holds.
Sowing and spacing
9 inches between plants, 18 inches between rows.
Chard seed is a cluster, not a single seed. Each "seed" is a dried fruit containing two or three embryos, so several seedlings usually emerge from one sowing point. That is normal, and it means thinning is not optional — leave the strongest and remove the rest, or all of them stay small and compete.
Sow half an inch deep. Germination takes 7 to 14 days and is improved by soaking the seed for a few hours first, since the corky seed coat holds water out.
The plant spacing calculator works out numbers for a bed, and the garden yield estimator gives a harvest range.
When to plant
About 2 weeks before your last frost. Chard is hardy enough to go out while frosts are still possible and tolerates cold far better than most leaf crops.
It can also be started indoors about 5 weeks before the last frost and transplanted, which gives an earlier start where springs are short.
A midsummer sowing is worth making for an autumn and winter crop. Chard is one of the most cold-tolerant vegetables and frequently overwinters, giving leaves when little else does.
The planting date calculator gives the frost-relative dates.
Varieties, including Bright Lights
Standard chard has white stems and dark savoyed leaves. Bright Lights and similar mixes give stems in yellow, pink, orange, red and white.
They grow identically and the flavour difference is slight — the choice is visual. Coloured chard is common in ornamental kitchen gardens and mixed borders precisely because it looks good enough to grow among flowers. Stem colour tells you nothing about taste or hardiness.
Growing in containers
Chard suits containers well. Allow 10 to 12 inches of depth, and space plants at the same 9 inches — or slightly closer if you intend to pick small leaves rather than grow full-sized plants.
A single large container of chard, picked leaf by leaf, supplies a household through a season more reliably than the same space given to lettuce.
Watering and feeding
About an inch a week. Chard is more drought-tolerant than spinach or lettuce, but leaves become tough and bitter if the plant is allowed to dry out repeatedly.
Feed for leaf, which means nitrogen. A single side-dressing mid-season keeps new leaves coming after the first heavy pickings. How to add nitrogen to soil covers which materials release fast enough to matter during a season.
Common problems
Pale winding tunnels in the leaves. Leaf miner — fly larvae feeding inside the leaf, which is why sprays do little. Remove and bin affected leaves as soon as you see them, and use row cover early in the season to stop the flies laying. This is the reason not to grow chard next to beets or spinach.
Bolting. A flower stalk, after which leaves turn bitter. Caused by heat, or by a cold check on a young plant that tricks it into behaving as a second-year biennial. Not reversible — pull the plant and sow again.
Downy mildew. Grey patches in crowded, damp plantings. Thin properly and improve airflow.
Slugs on seedlings. Chard seedlings are vulnerable for the first few weeks and largely untroubled afterwards.
Swiss chard belongs well away from beets and spinach, and pairs happily with bush beans.