Instructions: Watering

When to Water

Plants grow best when they are allowed to dry out somewhat between waterings (although they should never be allowed to dry out completely, or “bone dry”). They need to breathe (aka. aerate). To enable root aeration, it is crucial to allow the reservoir level to empty regularly (at least every 4 days or so).

A dipstick is included with each Gro-System pot to make it easier to tell when it’s watering time. Using the dipstick is like checking the oil level in a car, simply:

1) insert the dipstick down
the fill tube until it hits
the bottom of the pot,

2) remove dipstick,

3) check wet mark on
the end of dipstick.

Use the dipstick daily to check the reservoir level. Each Gro-System should be watered only when the water level drops to a certain level (showing no more than ¼” toward the first of the season). How quickly this occurs will vary, depending on plant type, weather conditions, and pot placement. Each pot will have different water needs. Because of this variance, it’s not a good idea to put Gro-Systems on a timed drip system since doing so would over-water most pots, but under-water others.


If the reservoir level isn’t allowed to drop down, the potting mix will remain saturated constantly, preventing proper aeration of plant roots (ie. drowning the plants). Ultimately, this results in root rot. One sign of over-watering is yellowing leaves. Over-watering can leave plants more susceptible to disease and infection (like Pithium Fungus, Powdery Mildew, and various viruses). For more information on over-watering, see “Over-Watering”.

Young Plants vs. Mature Plants

A newly planted pot may be able to go a full day before being watered (even if the reservoir is empty) because the potting mix can hold enough to meet the plant’s needs. In fact, we have found that watering from the top instead of using the reservoir provides adequate water to keep the drying cycle from 1-4 days during the first part of the season.

On the other hand, if the plants have grown large enough to hang below the bottom of the pot (especially with “water-hog” lime green sweet potato vine), they may need water when the reservoir level is at about 2” because the pot may not be able to go a full day without additional water. It is usually best to keep the cycle of drying at no longer than 4 days.

Just Because “You Can” Doesn’t Mean “You Should

Although Gro-System pots have large-capacity reservoirs, it is sometimes best not to fill them to overflowing. In the spring months of April, May, and the first part of June, plants are small and require less water. If the reservoir were filled to overflowing, it wouldn’t dry out for a week or more – causing root damage to the young plants.

This is especially harmful at the first of the season because it prevents the plants from establishing the solid root structures they will depend on during the hot summer months. Not using the reservoir, but instead watering from the top after the potting mix has been allowed to dry out a bit, is an effective way to avoid over-watering small, young plants.

Adding the Right Amount of Water

Some plants grow best with shorter drying cycles. For instance, calibrachoa (aka million bells) and some shade plants are highly sensitive to over-watering. It is important to adjust carefully the amount of water that is filled in the reservoir so the pot dries out every 2 or 3 days. If watering with a garden hose, this can be done easily by following these steps:

1) get a garden hose, an empty gallon jug, and a stop watch,

2) hook up the hose to a water-source,

3) turn the hose on to a moderate, constant water stream,

4) use the stop watch to determine how long it takes to fill the empty jug,

5) use the count from step 4 to add water (according to the current needs of the plant) into the reservoir.

For example, if it takes 10 seconds to fill a gallon jug, and the reservoir is taking 5 gallons each drying cycle, then fill the reservoir with a count of 50 seconds. *Note: it is best to cut the fill time short a few seconds to compensate for extra water metered between the time the hose is placed on the fill tube and the actual time the counting begins.