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| Water & Watering |
Water / watering is something most of us take for granted but don’t necessarily know its importance in gardening terms.
For instance; why do we water?
This is to replace water that is lost via transpiration from stomata (closable pores on the leaves).
That is, stomata open when the plant is ‘turgid’ ( swollen or distended with fluid) and are letting in air containing carbon dioxide.
When water, carbon dioxide and sunlight react they make sugars, these sugars are the plants energy source, this reaction is known as photosynthesis.
If a plant runs short of water, the stomata close and photosynthesis can stop, leading to slower growth and possibly the failure of flower buds to form and fruit to develop.
During the dryer summer months plants depend on reserves of water in the soil, when this is lacking it must be supplemented by irrigation to keep the stomata open.
This supplementary watering is important for the production of strong, healthy plants, i.e. plants that are watered sparingly but often produce a root system close to the soil surface and these roots soon suffer in dry periods.
The healthiest plants are those that develop a strong, deep root system which is able to tap into more reliable reserves well below ground level.
This then creates the problem of knowing when to water;
As a rule-of-thumb, a square metre of vegetation can draw the equivalent of about 25mm (1”) of rainfall from the soil every day.
There are a number of ways to establish if conditions are too dry; e.g.
Leaves can begin to droop.
The soil can feel quite dry when touched.
These two symptoms on their own do not necessarily mean the plant is suffering from lack of moisture, for instance when conditions are exceptionally hot, plants can wilt then recover when the temperature drop again, and the first few millimeters of soil may dry out in the sun making it feel dry to touch.
It is best to inspect the soil deeper down by excavating a hole to one spades depth, this will give a better indication of conditions at root level, and if watering is required.
Applying water;
Ideally one should apply water at a steady rate, in effect at a rate that emulates steady rainfall.
Too much water at once can cause soil erosion and compaction, plus it can wash away nutrients.
There are many types of equipment available to the amateur gardener for applying water to the soil, each with there own benefits and / or drawbacks.
Here are a few;
Watering cans ;
These can come in varying sizes (capacities) although two are quite popular, i.e. 1 litre (1¾ pints) and 5litre (2 gall).
The former is generally used with pot plants where only small quantities have to be treated, the latter are useful where there is a need to just water a few or individual plants as opposed to the whole bed.
Hosepipes:
Before using these one must ensure that there is no ‘hosepipe ban’ in your locality.
There are a number of ‘hose end’ attachments that can be fitted to hoses that allows the user to vary the intensity of the spray.
If the pressure is too great this can damage plants, spoil flowers, damage the soil surface, and wash out nutrients.
Similarly if too great, the water may run of the designated area before it has a chance to percolate down to the root system.
Sprinklers:
These tend to be used on lawns where they are allowed to spray water in a side to side or circular motion.
They have limited use on flower or vegetable beds due to the expanse of the spray, that is, the water goes on to areas that might not necessarily require watering to the detriment of the areas that do, meaning they use huge amounts of water.
Leaking / seeping hoses;
These are hose that have been purposely perforated to allow water to seep out.
In some cases these hoses can be used on the soil surface and placed adjacent to rows of plants where the water seeps out and percolates down to the root systems.
On other occasions, such as with permanent fruit trees and plants with deep root systems, the hoses are sunk permanently along the length of the rows of trees.
In both cases it is possible to fit the hose/s to reservoirs that allow soluble liquid feed to be added to the irrigation system.
Similarly these hoses can be fitted with automated watering systems where an electronic timer is screwed to the tap to turn the system on/off automatically.
Frequency;
Check weather forecasts this might eliminate the need to water at all.
It is better to water well rather than often!
If too little water is applied, this will only moisten the upper layers of the soil and it will not get down to the root system where it is needed, necessitating further watering a short time after.
If in doubt, check by digging a hole with a trowel / spade to see how far the water has percolated down.
Water only to an area consistent with the plants optimum spread.
Watering out with this area will encourage weeds and create a moist surface that is suited to slugs & snails.
Types of water;
Some plants need soft or acidic water to thrive.
Many domestic water supplies contain calcium and magnesium, which can raise the soil pH.
Water from recognized ‘soft water’ areas can have calcium added at the treatment works to improve its drinking quality.
Avoid giving hard water to ericaceous plants, as water above pH7 can cause chlorosis or yellowing of foliage, thus affecting photosynthesis and the subsequent health of the plant.
There are products on the market that will remove calcium and other impurities from tap water.
Rainwater collected in water butts is slightly acidic making it suitable for all garden plants.
To prevent the formation of algae cover the water butts to keep out sunlight.
What and when to water with a view to conserving water;
Never water plants when the sun is on them as this will waste water through evaporation.
Mulching over the soil surface will prevent evaporation and so help to keep the soil below moist.
Never add mulch to dry soil or the mulch will draw water away from the soil instead of holding it in, soak the soil first.
Bedding plants; need regular watering in dry weather, and are better watered either first thing in the morning or during the evening when the sunlight is not as strong.
Planting out at wider spacings can reduce the need for water,the closer plants are the more water they need.
Containers; can dry out very quickly in hot weather, and may need to be watered every morning and evening.
Revive hanging baskets and portable containers by soaking them in a bucket of water.
Established lawns; can survive a period of drought and will soon turn green again when rain arrives.
If is important to keep grass green give it a good soaking once a week.
In dry periods mow frequently but keep the mower blades at their 'highest' setting.
Close cropping can stress the lawn in periods of drought, whereas long growth will trap any dew.
New lawns; A lawn of newly sown grass seed or newly laid turf will need regular watering in dry weather.
Large shrubs and trees; deep rooted plants can find water for themselves and rarely need watering in dry conditions.
If they have been recently planted they will need regular watering until they have created a healthy root system.
Small shrubs; when established, can generally find water for themselves, and rarely need watering.
They will start to droop when they require water, when this occurs give them a good soaking in the early morning or evening when the sunlight is off them
Perennials; can be treated like small shrubs
Vegetables; Providing the ground was well prepared prior to planting vegetables can survive quite well without watering once they are established.
An exception can be on light or thin soils, the use of mulches can help in such situations.
Watering vegetables every 10-14 days should be sufficient for them to cope providing they get a good soaking at each of these occasions.
When sowing seeds give the drill a good soaking prior to sowing.
Similarly when planting seedlings flood the planting hole prior to placing the plant in the hole, this will ensure that there is moisture at the point where it is needed most.
Vegetables may need extra watering at the time when they are at their peak of development e.g. ripening or swelling.
Examples; crops such as legumes respond best to additional watering at flowering time
Watering Potatoes at flowering time will greatly increase the numbers of tubers and subsequent watering in dry spells will boost tuber size.
Root crops and alliums (onions) are less reliant on additional water so it is not essential to give them additional water.
Leafy crops such as lettuces and cabbages, ideally need a constant supply of water throughout their growth.
Where this is not possible, give them a good soaking 14-21 days before their intended harvest.
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