Container Gardens - Watering Properly

 

Fairhope, Alabama (Wiese Acres photo)

Even very large containers have more limited soil volume than garden beds, so proper watering and fertilizing are critical to maintaining a successful planting throughout the season.

The frequency and amount of water containers require depends on many factors, including the temperature, wind, type of container, type and number of plants. The length of time the plant has been growing also effects the amount of water necessary to maintain a healthy plant.  As the root ball enlarges, the soil becomes "crowded" and the water holding mass is decreased.  The more mature your container garden, the more likely it is to need watering more frequently to maintain the same moisture levels.

There is no set rule about when to water containers, other than to water what is necessary to satisfy the needs of the plants  It is important to watch closely and water whenever they feel dry according to the dictates of your plants.  If you have plants that prefer to be on the dry side, you'll probably want to allow the top inch or so of soil to dry out before watering again.  If you have plants that like consistent moisture, it's best to water them as soon as the surface of the potting soil looks and feels dry.

Plants should not be allowed to show signs of wilt before watering.  Wilting is a sign of stress and the health and vitality of the plant can be affected if wilting becomes severe.  When the root mass has become dry enough to cause wilting of the plant, it is also likely that the potting mix has pulled away from the sides of the pot.  When that happens, it is very difficult to re-moisten the potting soil.  Water tends to run right through the dried out soil mass and run out the bottom without being absorbed by the soil or the roots, or if the water can't escape through the drainage holes quickly enough, the entire root mass tries to float away.  Repeated, frequent, generous watering or placing the container in a larger bucket of water and allowing the soil mix to draw water in through the drainage holes until it is finished absorbing is the best way to "re-constitute" your soil.  When you see moisture on the surface of the planting mix, you'll know that it is sufficiently re-hydrated.

Each watering should be deep, adding water until it begins to run out the drainage holes at the bottom of the container.  This assures that you have moistened the whole soil mass.  It also allows for leaching of some of the fertilizer salts out of the soil.  Leaching is the process of washing away any soluble salts from the water and fertilizer so that they don't build up to the point where they cause damage to the plants, like burned leaf margins or burned roots.


Single emitter drip irrigation system

Watering can be done using a hand waterer or the garden hose, whichever is most convenient.  Certainly, if you can collect rain water and use that for all your containers, they will be happier than they will be with treated water, but that isn't always feasible.  If you have a location where your containers can be grouped together in close proximity, you can set them up with a drip irrigation system that can be purchased at any garden center.  These drip systems often are on a timer and water for a set period of time, whether the plants need it or not.  If you can find one that has a water sensor that tells it when to turn on and off, that will be much more efficient and will keep your plants much happier.

Simple drip watering system

A simple way to set up a type of drip irrigation is to cut the bottom out of a plastic water or soda bottle, stick the bottom end a few inches down in the potting mix, fill the bottle through the drinking opening, replace the cap and let the water slowly drain out into the soil.  This is helpful for those times when the hot, drying winds of summer try hard to suck the life out of your plants unless you water them multiple times during the day, or if you are going to be gone for a long weekend and don't want your containers to get too dry. 

There are moisture retaining gels available on the market, either already mixed into the "moisture-control" type potting mixes or sold separately to be mixed in by the gardener.  It is a polymer based product that looks like tiny pebbles or cystals in the potting mix when dry.  They are mixed into the potting soil when it is dry, according to label directions.  When wet, the crystals expand and take on the consistency of jello.  In their expanded state, they act as water reservoirs, slowly releasing water when the plant or the soil itself becomes dry.  These polymers don't eliminate the need for watering, but they do provide a little bit of a cushion for gardeners who might have things to do other than standing and watching for just the right time that their container gardens needs watering.

There is some evidence pointing to a downside of the moisture gels.  It appears they might tie up the fertilizer in the gel substance, making it less available to your plants.  As long as you are aware of this and increase the frequency of your fertilizing accordingly, the benefits probably outweigh the risks.

We'll talk more about fertilizing tomorrow.