How to Grow Spinach Seeds
Grow Guide #2320
Binomial name: Spinacia oleracea
Life Cycle: Biennial (usually grown as an annual)
This 'How to Grow' guide details everything a home gardener needs to know to plant, grow and care for Spinach (Spinacia oleracea).
Some plants are known as 'spinach' but are different species botanically. Perpetual spinach (Beta vulgaris var. cicla) is actually a type of silverbeet that is harvested while the leaves are small and tender; it should be grown like silverbeet. Malabar spinach (Basella alba) is eaten as a substitute for spinach but is grown as a tender perennial vine with different growing requirements to spinach.
When to Sow Spinach Seeds
Spinach can be grown year-round in most climates. Avoid planting in extremely hot or cold weather which can affect germination and growth. Use the table below to identify the best time of year to sow spinach in your climate.
Spinach plants are best grown in full sun or part shade. Choose a location that will receive at least 3 hours of full sun each day.
Spinach plants need a well drained soil enriched with plenty of organic matter. Prepare soil by weeding it thoroughly, digging it over to loosen it and adding aged animal manure or compost. Keep the area free of weeds until planting. Learn more about preparing soil for planting here.
Spinach plants can be grown in containers. If possible choose a variety that’s recommended for container growing. Use a good quality potting mix and make sure your container is large enough for mature plants; a minimum of 20 litres is recommended for spinach. During the growing season, keep in mind that container grown plants may need additional fertiliser to encourage healthy growth.
How to Sow Spinach Seeds
Spinach seeds do not require any treatment (eg soaking, stratification) before sowing.
Spinach seeds grow best when they are sown directly into the garden.
- Sow seeds directly in the garden 8mm deep and 25-35cm apart, with rows 40-50cm apart.
- Keep soil moist but never wet or dry.
- Seeds should germinate in around 5-10 days at a soil temperature of 4-25°C.
- Young seedlings will need protection from pests, pets and weather until they are established.
Spinach is a cool season crop that will bolt in very hot weather. Do not transplant seedlings or sow seeds outside in very warm temperatures.
Tip: Spinach seeds can also be sown in the less formal ‘scatter seed’ method. Simply roughen the soil, scatter seeds evenly over the surface, then smooth the soil over lightly to cover the seeds.
How to Grow Spinach
Spinach plants may need watering during the growing season. Water when the soil is dry about 5cm below the surface (test this by scratching away a little soil with your finger). Water deeply in the early morning or late afternoon. Avoid watering the leaves of plants to avoid fungal diseases. Learn more about watering here.
If soil was well prepared no extra fertiliser should be necessary. In poor soil or to give your plants an extra boost, application of a high-nitrogen fertiliser or one formulated for leafy greens or herbs can be beneficial:
- Apply slow release fertiliser at the recommended rate when transplanting or when seedlings are 5-10cm tall.
- Apply liquid fertiliser at the recommended rate and frequency during the growing season.
Optional: To give plants room to grow, thin seedlings when they are large enough to handle. Pull out any weak or small seedlings so plants are spaced about 25-35cm apart.
How to Harvest Spinach
Spinach should be ready to harvest in approximately 50-100 days.
Spinach is ready to harvest when the leaves are large enough to eat. Harvest individual leaves by cutting them from the plant. Alternatively, whole plants can be harvested by cutting the stems at ground level. Spinach is best eaten soon after it is harvested. Leaves can be stored short term in a perforated plastic bag in the fridge. For longer term storage spinach can be blanched and then frozen.
Common Problems when Growing Spinach
Like all plants, spinach is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing spinach plants:
- Aphids are small (2-4mm long) sap-sucking insects that congregate on the new shoots or the undersides of leaves. They can cause leaves to wilt or become discoloured, and also excrete honeydew which can attract ants and other insect pests. To manage aphids, remove them by spraying with a garden hose, apply a soap or alcohol spray, or encourage predatory insects to your garden. Read more about aphids here.
- Bacterial leaf spot is a disease that causes irregularly shaped brown spots on all above-ground parts of a plant. The spots at first appear to be wet but become dry and scab-like over time. Leaves and flowers can fall prematurely. Water plants at soil level (not on the leaves), dispose of fallen leaves and fruit and practice crop rotation.
- Bitter taste can be caused by plants growing too slowly, suffering a setback in growth or being harvested too late. Enrich soil with aged manure before planting, ensure plants are watered deeply and regularly, and harvest when they are young and tender.
- Bolting is when a plant prematurely flowers and goes to seed. Bolting can be caused by a period of extreme weather. Avoid sowing seed until after the danger of frosts has passed or in very hot weather. Water plants regularly and deeply in hot weather to prevent them suffering heat stress.
- Damping off is caused by a fungal growth that transfers from the soil to seeds or tender seedlings. Seeds may appear not to germinate, or young plants start to rot when they emerge from the soil and become soft and mushy at the base before dying. Use new potting mix if raising seedlings, do not water foliage and avoid waterlogged soil. Read more about damping off here.
- Downy mildew is a fungal disease that causes yellow to grey-brown patches on leaves, especially the undersides. Water plants at soil level (not on the leaves), remove and destroy affected leaves and do not overcrowd plants to ensure adequate air flow. If problems persist, spray with a homemade milk spray or fungicide.
- Slugs and snails are molluscs that feed on tender leaves and shoots, mostly at night, leaving slimy trails behind them. Control them by removing their hiding places, keeping free range poultry, collecting them by torchlight or by placing traps. Read more about slugs and snails here.
- Yellowing leaves are a sign of nutrient deficiency. Apply a nitrogen-rich fertiliser or one formulated for leafy greens or herbs at the recommended rate. A liquid or foliar fertiliser is a good option for restoring nutrients to the plant quickly. Water the plants deeply after applying fertiliser and avoid heat and water stress to allow the plant to recover.
- Whitefly is a sap-sucking insect related to aphids. They are often found in large numbers on the underside of leaves and will swarm in clouds when disturbed. Plants may have yellowing leaves or may wilt, and growth will be slowed. Whitefly can be removed with a garden hose or sprayed with soap spray. Badly affected plants should be destroyed. Attracting beneficial insects that will prey on whitefly can be beneficial. Read more about managing whitefly here.