Auckland Botanic gardens

Growing plants from seed is satisfying, saves money and is easier than you might think. Some seeds are best sown into pots or trays and grown on in small containers or punnets until ready for planting. Others can be sown straight into garden beds.

Obtaining seeds

• A wide variety of seeds are available by mail order. For summer plantings check through seed catalogues during winter and order seeds early, so you are ready to go for spring and summer planting. Order seed for winter crops in summer as these are mostly sown in February/March and planted in April.
• Use fresh seed (don’t use expired seed packs or ones that have been open for a few years) to ensure the best germination rates. Seed is best stored in a container in the fridge to keep them viable for longer.

 Sowing seed in trays

• A greenhouse is ideal for sowing seed in trays.  Small versions of a greenhouse or cloche can be purchased.  These can be quite small, just large enough to accommodate a few trays or pots. Alternatively, find a warm, sheltered spot that is not too hot and sunny. Sometimes a warm window sill is suitable, provided it does not receive direct sunlight.
• Generally, vegetables and annuals are sown 4 to 6 weeks before you intend to plant out.
• Sow seed into a seed sowing mix. It will have good water holding capacity and drainage, and low nutrient levels. (Ordinary potting mix has higher nutrient levels that can harm young seedlings).
• The finer your seed, the finer you want your mix (so the tiny roots can be supported by the soil particles) so sieve out any large chunks.
• Lightly pack seed sowing mix into pots or trays and gently press, so you have an even surface.
• Before you sow the seeds, water with a watering can so that the mix is damp.
• You can sow in shallow trays, pots, or even egg cartons or toilet roll pots. If you sow individual seeds in these biodegradable materials, the whole container can be planted into the garden when it is time to transplant. It is a less disruptive way to transplant.
• As a general rule, sow seeds at a depth of about twice their size. Some especially fine seed doesn’t need covering at all so can be surface-sown.
• Empty a few seeds into the palm of your hand and start at one end of the seed tray. Gently tap your palm to sprinkle seeds onto the seed sowing mix evenly.
• Once the seed is sown cover it carefully with more seed mix. Seed that is especially tiny like foxglove (Digitalis), lobelia or impatiens, requires little light to germinate so will not need covering. It should tell you on the seed packet if this is the case.
• For larger seed you can use a pencil to make a hole, then drop the seed into it and cover with more mix. Water in well with a watering can with a fine sprinkler head, so the water does not wash the seed around.
• Once seeds are sown, cover the tray with a small sheet of plywood, cardboard or other opaque material to keep moist in and light out. Most seeds do not need light to germinate.
• Immediately you notice signs of germination remove the cover from the container.
• Keep the seed sowing mix moist but not too wet, and always water gently. You can place the seed containers in a tray to water, so it seeps upwards, or use a watering can with a fine head.
• Make sure to label each batch of seed with the varietal name and date of sowing.
• As soon as young seedlings are large enough to be handled, they can be transplanted into pots or punnets. Usually, they are ready when the first true leaves emerge (the second set of leaves to emerge after the seed or cotyledon leaves).
• Always lift seedlings out from beneath the roots, using a bamboo skewer or ice cream stick to gently prise them upwards.  Never lift by their stems.
• Transplant the seedlings into their new container at the same depth they were growing in their seedling container.  Avoid burying the stems, or the seedling may rot.
• Grow the seedlings in a warm, sheltered place until ready to be planted in the garden.

Direct sowing

• The general rule when sowing seeds directly into the garden is to sow at a depth of about twice the seeds size.
• Work the soil to a fine texture and rake the surface evenly. Using a hoe, the edge of a rake or similar garden tool, make a furrow at the depth you want to sow your seeds. The depth ranges from very shallow for fine seeds such as lettuce, to several centimetres for larger seeds such as sweetcorn and beans.
• Once sown, cover seeds with a fine layer of soil that has come out of the furrow. Gently pat the furrow down with the back of the rake and water in well. Very fine seed like carrots or lettuce can be covered with a fine layer of commercial seed sowing mix.
• When sowing seed into furrows, you can hand-place larger seeds and evenly sprinkle smaller seeds. If too many seeds germinate, thin out the excess. These can be replanted elsewhere if needed. 
• Once seeds are sown, keep the soil moist but not saturated.
• Make sure to place a label with the name of the crop and sowing date at one end of each row.