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, 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 page to find out about different options for watering equipment and watering systems.
When to water
Twice a day before germination and until 3 cm 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 3 cm 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.
In addition to daily watering seedlings need daily maintenance to ensure even growth, prevent seedlings getting too big, remove weeds, check for pests and disease, prune roots and thinning out extra seedlings so that one healthy seedling is in each tube.
Getting even growth
Seedlings will grow reaching toward the sun. As your seedlings grow, sort them out by height. Put the smaller ones at one end of the box and turn that end of the box to the direct sun so the tall ones don’t shade the small ones.
Seedlings with full sunlight will always grow faster than those that are in part or full shade. Rotate your seedlings to make sure they all get the same amount of sunlight. You may need to move your boxes as the season changes and the sun moves.
The seedlings in the centre of the box are being shaded by the ones on either end. You can see the box was rotated but the seedlings in the middle should have been brought to the outside to get even access to sun.
Never leave your seedlings in full shade, unless they are getting too big and you want to slow down seedling growth. Back off watering as well so that the seedlings do not get leggy and weak.
Too little sun and too much water will cause your seedlings to be leggy and weak (below left). Uneven growth at front of box due to shading by larger plants (below right).
The right balance of sun and water will produce robust seedlings – remember that after your seedlings are 3cm tall they get 1 good watering once a day in full sun.
Rotating seedlings and moving boxes also give you a chance to check for pests and disease. Rotate boxes frequently to prevent all sorts of crawlies can find habitat between nice moist cool spaces between your boxes.
When seedlings are getting too big
If your seedlings are 20-25 cm tall with a strong root structure they ready to be planted out on the land. However, if the winter rains have not come they cannot be planted out. You will need to slow your seedlings growth down. The leaf structure above the tube cannot be allowed to grow so large that the root inside the tube will not support it without daily watering.
To slow the seedling growth down put the seedling in semi shade and back off the amount of water it is getting. Depending upon weather conditions water every day and a half or every other day. The months that you will be doing this are after March and the weather will have cooled a lot. Do not let the seedling wilt – it will slowly harden up and rely on less water.
The seedlings on the left are the right size for the root structure in the tube. The seedlings on the right will struggle to survive without its daily watering. The root system is not large enough to sustain the head of the seedling after planting – they will have to sustain themselves in a harsh environment after planting out.
Important to pick out weeds early so they don’t get the opportunity to establish themselves. Weeds will compete for nutrients and water depriving your seedlings of the elements they need for maximum growth and strength.
This particular species in the picture comes from a bulb which can be difficult to remove without disturbing the seedlings root structure. You will need to tap the seedling out of the tube and ensure you get every bulb. This weed is real problem if planted out with the seedling.
Checking for pests and disease
Whilst watering check for pests and disease. Any eaten leaves or stems cut off is a sure sign that there is something eating your seedlings. Check between tubes and the bottom of tubes for slugs, snails and other creatures that like cool dam places to live. Search and find the culprit! A great deal of damage can be done in 24 hours.
Curled leaves is a sign of larva within the curl.
Discoloured, potted or excessively wrinkled leaves is a sign of disease.
Eventually the seedlings will need to be planted out. Roots growing through the bottom of the tube will be damaged at planting time. It is a severe shock for plants to lose large amounts of root growth. Trim back regularly as they grow. This can be achieved by firmly rubbing a hand across the bottom of the tube.
Check the roots at least once a month. It is also a good chance to have an individual look at each plant.
To prevent seedlings from growing excess roots out of the tube base, aerial pruning may be used. The tubes are suspended with their bottoms exposed to the air or placed in commercial seedling trays – this does increase the risk of the tubes drying out so where this method is used monitor progress closely.
Excess seedlings should be removed by cutting them off right at the very base of the stem with a sharp pair of scissors. Follow hygiene requirements and clean scissors prior to use. Leave 2 seedlings in the tube. Cull the weaker of the two in a month. Cutting off the seedlings means that the roots of the surviving seedlings will not be disturbed.
Once plants have reached a juvenile stage then they must be thinned to one plant per tube.
If multiple seedlings are left in a tube, they will compete with each other for space, water and light. The result will be weak and unhealthy seedlings prone to disease, particularly fungal infections.
Before thinning check with the co-ordinator to make sure there are no other growers for that landowner who might need extra seedlings.
If you have empty tubes from other species that you have not been able to fill the extra seedlings can fill these empty tubes. Tubes with multiple seedlings are useless for the landholder and will be rejected at the planting out stage and thrown out! Remember, our objective is one healthy plant per tube.