Monday, December 10, 2012

Water Woes

The last article I wrote dealt with sunlight and what is considered “Full Sun”. It was inspired by questions that I get when someone has an issue with a fruiting plant that is not producing fruit. Today's article has also been inspired by questions that I get when a plant is not doing well. It is probably the number two most common problem I deal with as a Master Gardener.

Many of the websites and articles that I read have a sentence in there that drives me crazy! It goes something like this, “This plant needs one inch of water per week” or something along those lines.
WHY, does that sentence bother me so much?
Lets run a couple of scenarios.
You have your favorite plant, it doesn't matter what it is for this example, it has a tag or you have read that it requires one inch of water per week. Okay, fine. What if this plant is in a very sandy soil? Water drains exceptionally well in sand, because it has little to no water holding capabilities. That one inch of water will be gone in hours, the plant is not getting any water 3-4 days later.
Let's reverse it. The plant is in a very heavy peat based soil. Peat holds water very well. That one inch of water may still be around in a week. Then you water again. It continues to build up until the plant literally drowns. More on that in a minute.
So you need to be aware of the type of soil it is in. What about the pot itself? 

A terracotta or clay pot is very pretty. They are nice and heavy and help to stabilize the plant. That clay or terracotta actually wicks the water away from the soil. So here again, one inch of water will be gone in a shorter period of time than one week.
Plastic pots tend to retain the water better. You guessed it, one inch of water per week might be too much.

There are numerous other things that need to be taken into consideration. The type of plant is a big one. A Cactus will need MUCH less water than a Philodendron. I know, the Cactus label does not read one inch of water per week. I have actually met somebody that watered theirs every other day, their's a plant and they need water. Of course, there was also the case of a woman that literally...I can't make this stuff up...watered her large Cactus one tablespoon of water every 6 months and wondered why it was looking poorly.
Size of the plant is another good example. Which do you think will need more water in full sun, a four inch pot or something the size of a trash can?
How about the weather? Do you think a week of cloudy, overcast, cool weather will need more water or less water than 95 degrees, cloudless sky, and windy?
It will also matter greatly if it is in the ground or in a pot.
Hopefully that has given you some idea of why you need to know your plant and the situation it is trying to be grown in.
What is that you say? How do you know if you are over-water or under-watering?
EXCELLENT question!
Sometimes when plants start to show symptoms of stress, i.e. wilting, the first reaction is to water, but sometimes over-watering can be just as detrimental to a plant's health as under-watering. Symptoms of both over and under-watering can look very similar. Leaves turn brown and wilt. Often times, when this happens to under-watered plants, those dead leaves will be dry and crispy. While with over-watering, those leaves may still be soft and limp.

Here is a test: Is this from over-watering or under-watering?
Tough to tell huh?

With under-watering the plant tries to conserve what little water it has by keeping the stalk green and the roots moist, but the leaves will turn yellow and wilt and eventually dry up.
With over-watering, plants need to breath. They breath through their roots and when there is too much water, the roots cannot take in gases. It is actually slowly suffocating.
Both over and under-watering can lead to other things, such as stunted growth, and lack of fruit or flowers.
Many people like to use a water meter on their plants. If you are not familiar with these, it is usually a probe that you stick in the soil and it will tell you whether you need to water or not. One of the types looks like this:

 I don't like them because they are very unreliable. I tried one once, I stuck it into a pot of extremely dry soil, I know it was very dry because it fell out in one piece and was very light. The meter said it was fine, do not water.
You actually have a reliable water meter with you right now. Scientifically it is called “the index finger”. Stick that scientific device into the soil, about 1-2 inches....if it feels dry, water...if it is damp, don't and check again tomorrow. Pretty cool huh?!
For smaller plants there is another method. Water the plant very well, make sure there is water coming out of the drainage holes. Then, lift the pot up. Get that weight in your head. After a couple of days, lift the pot again. If it feels much lighter than the other day, water, if it still feels heavy, check again in a couple of days.
I have been known to use both methods. I will stick my finger in a pot, then lift it. I very seldom have a water issue problem.
Hopefully, this has shed some light on the subject of watering. If you MUST err one way or the other, do so on the under-watering side. Many plants are much more drought tolerant than we think and will recover from too little water. There are not many that will come back from a dip into the deep end of a pool, unable to swim, with no life preserver!    
Happy Growing!