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When & How to
Water Your Plants

Grandson's preferred watering method
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Very frequently we get the question "how often should I water my XYZ plant?"

First, imagine two identical plants in size, age, and soil

   Light

If you place Plant A in a sunny window with 6+ hours a day of sunlight and Plant B in a northern window, watering requirements will vary dramatically

Plant A will dry out much faster due to greater warmth and therefore greater plant respiration (breathing/sweating)

So, same plant, different needs based on location via the light they receive

   Soil

Another huge variable is soil / soil drainage.  If you use low or poor quality soil (thick / heavy) water is retained much more than what professional nurserymen use, which is a very loose, rapidly draining composition

With an ultra loose mix, for example, you could theoretically water a cactus every day

So think Plant A and Plant B again.  If different soils, their watering needs will vary, and possibly dramatically

By the way, one does not water a plant
...you water the soil

The soil holds the water available for plant roots to withdraw.  Plants do not draw water directly, like you drink a glass of water ...it's a slow uptake that takes several hours to drink

   Pot Size

Next think pot size and pot material.  Terra cotta breathes and plastic does not.  Glass, and metal are the same as plastic.  More or less water is needed for identical plants based on the pot material

The larger the pot (compared to the size of the plant), the more soil = the more water retention, i.e. the more water is available to plant roots.  A smaller pot holds/accepts/retains less water, so with a small pot you water more often

   Temperature

If you like a cool house, your plants' respiration rates are slower than a warmer home.  Less water is needed for Plant B in a cold room versus Plant A in a warmer or hot environment

   Plant Size

Obviously, a small plant needs less water than a large plant.  But as that same plant grows, more water per application is needed, perhaps, a larger pot as well.  When folks email and say "how much water?" the plant size is very important to a good answer/guess

   Water Quality

Today, most folks have tap water of marginal quality.  The water has been treated with who knows what before it is fed to your home kitchen.  Plants are EXTREMELY sensitive to water quality so if your water is treated, chances are, over time, your plants will be hurt by a slow toxic effect

Rain water is the best water for every plant.  Try to collect rain and keep it available for your houseplants.  Otherwise, use a home carbon filter (a la Brita) to clean your water.  Always water with room temperature water

   Plant Variety

So, for sure you expect to rarely water cactus and succulents.  How rarely?  For example, we have several of each indoors and water about every 20-25 days

Some plants varieties, like ficus, enjoy plenty of water "available" (held by the soil) when they want to drink.  We emphasize "available" as this is water contained in the soil.  When you add new water, that water is not available to your plant.  The water must be absorbed by the soil and then the roots can withdraw moisture.  So, you do not actually water the plant, you water the soil.  So that is another reason soil composition and quality are critical variables

Most philodendrons, for example, want lightly moist soil and zero new water until the soil is dry to very dry.  They are jungle plants growing in shade to deep shade in native lands.  It's warm, the air is still, the soil is lightly moist and dries out slowly

When you buy a new plant, get the Latin name so you can look up what it is the most likely natural water schedule

When you know where your plant is native, it is much easier to guess water and soil needs

   Watering Rule

It is almost impossible to harm a houseplant with TOO LITTLE water.  You have to learn each plant you have and provide the LEAST water it will be happy with.  This involves some knowledge (of that plant) and testing

Find out by testing when a plant will limp or become stressed.  The ideal time to water would be the day before limp sets in

Therefore, if you have a variety of plants, watering on a schedule, e.g. every Monday and Thursday, is wrong

Some plants may need 2X weekly water.  Others may need 1X weekly, others 1X monthly

   Clean Foliage

Most folks don't clean their plants.  Outdoors in Nature (where every plant in the world came from) rain and wind clean the foliage.  Indoors, you need to assist

A soft cloth, slightly damp, is the best cleaner.  Wipe BOTH sides of the leaves.  It is the underside of leaves most insect pests go for, so cleaning wipes them away.  Frequent cleaning can eliminate almost all bugs

The other reason is for photosynthesis and breathing.  Clean plant leaves work better to feed the plant.  Dirty leaves choke the plant and invite insects

   The Trick

Until you know your plants as individuals, one trick is to sample the soil with your finger.  Stick your finger into the soil down about one knuckle.  If you feel ANY moisture at that depth, your plant does not need water

Think about where the roots are - certainly deeper than your first knuckle.  If the soil is dry down 11/2 to 2 knuckles, now you can consider adding clean water

Advanced plant care students will determine the answer (is it time to water?) just looking at the top of the soil's appearance

With quality soil, the rule is to water thoroughly.  Wet the soil so all of it is soaking.  This often (starting with dry soil) takes several applications of water at intervals (a minute or two apart per application) as dry soil tends to repel water

This does not mean there is any standing water.  For example, DO NOT use dishes beneath plants to collect water.  The dish must be EMPTY of all water after thorough watering.  Water caught at the bottom of the pot breeds fungus and root rot and trays encourage those problems