Establishing a general watering schedule for your plants is impossible. Room temperature, relative humidity, size of plant, rate of growth, size and material of the container, potting soil and type of plant are all factors regulating watering frequency. The important point is to water only as often as the plant needs it.
Improper watering, especially overwatering, is the most common cause of house plant problems. Roots need air as well as water. If the soil is constantly saturated, air cannot reach the roots and they suffocate. Excess water becomes stagnant and sour. Soft spots develop which may lead to rot, and leaves yellow and fall. A plant is weakened by overwatering and becomes susceptible to disease, particularly fungal attacks. Sub-irrigating and double potting reduce the risk of overwatering by providing an evenly moist soil.
Overwateringis seldom a problem if soil drainage is adequate. If the soil remains very wet three or four days after watering, it is quite possible that there is poor drainage. The soil itself may be too fine or contain too high a proportion of organic matter. In this case the plant should be repotted in a soil containing more drainage material, such as sand or perlite. Check the drainage holes in the bottom of the pot to make sure they are not clogged. Clogging can be prevented by placing bits of broken pottery or small pebbles directly over the holes before adding soil. If there are no drainage holes, cover the bottom of the pot with at least 2 - 3 cm of pebbles and water with care. All the soil must be moistened, but not to excess.
Underwateringis equally harmful, but easier to prevent. Plants not receiving enough water wilt from the top down and leaf edges turn brown. If the plant dries out badly, do not try to compensate by drowning it in water, You may find the first watering drains right through the soil; keep supplying water until the soil begins to absorb it. Keep the plant out of heat and light until it recovers, Misting the leaves speeds recovery.
Watering Methods
Plants fall into two categories according to how they should be watered. A plant care encyclopedia will specify the conditions each plant prefers.
| 1. | Drench thoroughly, then let the soil become moderately dry before rewatering. The top 1 cm layer of soil should be crumbly and dry. This method is used often for plants with thick roots. |
| 2. | Keep evenly moist, but never wet. Many plants with small fibrous roots prefer this method, because their roots are more susceptible to root rot or burning. |
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An indoor potted plant should not need daily watering. Such a need could indicate a pot-bound plant (one whose roots completely fill the pot).
There are various watering methods, each with pros and cons. Watering from the top is convenient and simple, especially using a watering can with a long narrow spout, Be sure to moisten the soil throughout, adding enough water so that some will drip out the bottom of the pot. A common mistake is to sprinkle a little water on every day or two. This keeps the top layer moist while allowing the tender absorbent root tips to dry out and die. It also encourages roots to grow only in the top layer of moist soil, where they are no longer able to utilize the available soil nutrients or support the plant.
Use care when watering from the top. Splashing water on the leaves causes spotting and encourage the spread of harmful micro-organisms. Water left standing in the crown provides a site for the development of root rot and other fungus disease (exception - Bromeliads). Add the water slowly, to avoid washing soil away from the base of the plant.
Bottom-watering ensure thorough watering. Plants in porous clay pots can be set to soak in a pail of water, deep enough that the water level does not rise above the rim of the pot. Water soaks in through the bottom and sides of the pot. Leave it in for about one half hour, until the top of the soil feels moist.
The same results are accomplished by standing small pots in a dish of water until moisture appears on the surface. Never leave plants standing in water for any length of time.
Salt build-up becomes a problem if bottom-watering is used constantly. Water often contains high salt levels, especially in Aiberta. These are deposited in the soil, and can easily build up to levels toxic to plants. Fertilizer deposits excess salts in the soil also. If the problem becomes severe, a white crusty layer appears on the soil surface.
To prevent the build-up of toxic salt levels within the pot, alternate bottom-watering with top-watering, as top-watering leaches away excess salt. To remove salt deposits, water the plant thoroughly from the top let drain, and water again in half an hour to wash away dissolved salts.
Another method occasionally used is to completely submerge the pot in a pail of water until air bubbles cease to rise. Remove and allow the plants to drain freely for 20 minutes.
Sub-Irrigating
This self-watering system is ideal for people frequently on vacation, and takes the guesswork out of watering. Plants draw up moisture as they need it.
Take a length of glass-fibre wick, coarse rope of heavy wool, and insert the top 5 cm through the drainage hole of the pot. Pack fine soil over the wick, then fill the pot with potting soil. Place the other end in a nearby tray of water.
Heavily chlorinated water should stand in a bowl overnight to allow chlorine to dissipate.
Soft water will harm a plant unless it has been through a deionizer. Water softeners merely replace calcium ions with sodium ions, which are equally harmful in high concentrations. During spring runoff, tapwater may be too salty for use on plants. If you suspect your plants are suffering from water of high salt content, use rainwater or melted snow.
Watering plants at nightis a poor practice. Transpiration and evaporation rates are reduced by cooler temperatures during the night. Cool nights and wet plants provide ideal conditions for fungal attack.
