Water is necessary to activate the seed and begin the process of germination. The seed will absorb water and swell activating dormant enzymes and develop new enzymes that help the seed to utilise stored food created during embryo development. There must be sufficient soil moisture to supply a continuous source of water and nutrients to the seed to supply the internal cell division. This is the reason why the soil must remain damp until the seed has completed germination and has sprouted.
Once you have sown your seeds it is very important to water with a gentle, fine spray twice a day until the seedlings are 3 cm high. After seedlings are 3 cm high they get full sun and a thorough watering once a day using a regular shower setting.
Some species require a more stable moisture content to the soil. These species will require capillary watering.
Any method which fills the tubes to overflowing or disturbs the gravel will wash the seeds up and away. Forceful pressure will blast seeds out of the tubes! Always water thoroughly - the water must wet ALL the potting mix in the tube.
At all stages through the growing season, the seedling tubes should never dry out completely. Be vigilant and check your seedlings daily. The tubes can dry out due to hot windy weather or insufficient watering.
If by chance your seedlings do dry out (we hope not!), try soaking the entire box in a tub of water (individual tubes if no tub is available) until the air bubbles stop rising. DO NOT leave the seedlings in water more than a couple of minutes - the nutrients will leach out of the tubes and seedling may drown.
In summer months ensure the residue water in the hose is emptied out before watering seedlings. If the hose has had any sun on it the residual water in the hose will be very hot and will cook the seed/seedlings.
Different ways of watering
Please go to the Equipment and Set Up page to find out about different options for watering equipment and watering systems.
When to water
Twice a day before germination and until 3cm tall
Before and during germination (usually first 6 weeks) and when seedlings are very small you must water once in the morning and once in the afternoon to keep the potting mix constantly moist. If you fail to do so, you could lose all your seedlings on one hot day! This means hand watering 3-5 minutes per watering.
Once a day after seedlings are 3cm tall
When seedlings are established, a thorough watering once a day in the morning will be enough in normal weather. Only hot windy days require an additional watering.
As the weather conditions change, so must the watering regime. Seedlings will require more water on hot windy days. When rainy weather sets in, water only when needed. Autumn days get a bit cooler and we have more rain, watering every second day may be sufficient – but always check!
In cooler weather, ensure that you only water in the morning. Watering in the evening encourages fungal diseases (e.g. powdery mildew) when the plants stay wet overnight.
It also encourages snails and slugs to graze on your seedlings.
Too much watering can cause:
- The seedlings to grow too fast and become spindly
- The cells in stem to burst killing the seedling
- Collar rot or damping off
- The seedlings to drown
- Formation of moss and lichen on top of soil preventing aeration and causing soil to too remain damp and soggy. This usually occurs if the seedling is not getting enough sun as well.
- The root system to become weak and dependent on frequent watering causing roots not to develop enough strength to survive the harsh environmental conditions when planted out. The root system grows and strengthens as it reaches out looking for water.
The root system will become stunted because the soil in the tubes has not been completely saturated resulting in most of the water remaining at the surface of the tube. With sever under-watering the seedlings will stress and become limp.
Ensure that the seedlings are all receiving the same amount of water. If you have a sprinkler watering system, check regularly that all seedlings get adequate water, particularly those around the edges of the boxes. This image show the results of a sprinkler system that did not water evenly causing some seedlings to be stunted.