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Sub Irrigation Planters: Is A SIP Right For You and Your Plants?

Self-watering planters or Sub-Irrigation planters (SIP) are the perfect choices for anyone wanting to take up container gardening.

However, self-watering pots are ideally suited for busy individuals, forgetful people and those who have not had good luck with plants in the past.

how sub irrigation planters work

SIP provides an easy, affordable, care-free way to enjoy planting veggies, flowers and herbs on your deck, balcony or patio, in your basement (with LED grow lights) or near a sunny window in your home.

In this article, we will share answers to your questions on the use of these innovative containers. Read on to learn more.


What Are Self Watering Planters?

Regular planters and flower pots have holes in the bottom allowing any excess water to drain out the bottom or into a drip tray or saucer. Drainage holes are a good thing. Too much water causes root rot, a common reason for plant death.

Some self-watering planters also have holes in the bottom, but these holes allow water to flow in.

Instead of a drip tray, this type of SIP has a removable water reservoir which you can fill directly when the water level is low. The pot containing the plant sits above the reservoir, and water is drawn into the potting medium through a wick.

Mature plants with fully developed root systems may send roots through the holes in the bottom of the pot and into the reservoir, to access the water. Either way, this method ensures the plants get the correct amount of water.

Another type of SIP has no holes in the bottom.

Instead, the exterior of the planter has a closed bottom and holds several inches of water. Water is replenished via a tube (often a PVC pipe) running from the soil surface to the reservoir.

A strategically placed overflow hole in the side of this container ensures the reservoir level is never too high. A platform or screen holds the plant above the water level.

A small area of soil comes in contact with the water acting as a natural wick. This type of planter usually includes a gauge to inform you when more water is needed.


What Are The Advantages Of Self-Watering Planters?

Maintaining a garden can be time and labor intensive. This is especially true if you live in very challenging climate (as is more and more the case these days). If you are facing drought conditions or unpredictable, inclement weather, gardening success is at times elusive.

Even in the best of conditions, balancing all of any plants’ needs can be difficult. Providing the right amount of sunlight, nutrition, and water for plants to support healthy growth from seed to maturity is a challenge. Throughout the plant’s life, you must be vigilant about any disease, pests, and weeds.

These reasonably high maintenance requirements make gardening an excellent pastime for retired people and others who have lots of time on their hands.

Unfortunately, for the average person, it can be nearly impossible to balance the demands of everyday life, much less take care of a garden.

Since successful gardening with even very few plants is an excellent way to relax, reduce stress and potentially save some food dollars, having to forego the activity is a shame. [source]

People who travel a great deal for work or recreation also face challenges when it comes to maintaining plants.

Plants need water regularly. If you are away a great deal, it may be difficult or impossible to find someone dependable to water your plants. With SIP you don’t need to worry.

Fill the water reservoir before leaving and count on having your plants properly watered for a couple of weeks.

Self-watering planting containers solve a lot of the problems associated with traditional gardening.

Even if you live in a small apartment, have kids to care for and work several jobs, you can set up a few containers of veggies, herbs and/or flowers to brighten your space, improve air quality and make healthy contributions to your dinner table. [source]

Watering is one big gardening chore which self-watering planters can dramatically reduce. Instead of watering every two or three days, you can expect to simply check and refill the reservoir once every couple of weeks.

This interval may vary somewhat depending upon the potting medium, the size, and types of plants grown, but it is fairly constant and reliable.

You’ll want to check frequently when first starting out to get a feel for how often the water reservoir needs refilling. During very dry weather, you may need to refill the reservoir water more often.

Using SIP for controlled, container gardening also means you don’t have to do any digging, hoeing or weeding. If plants are indoors in a controlled environment, you will be far less likely to experience problems with pests.

Additionally, many pests are attracted to plants suffering from over-watering or under watering. The correctly watered plants growing in self-watering systems will be less likely to attract them.

Proper placement of planters in a sunny window and/or using grow lights on a timer eliminates worries about providing the right amount of light.


How Is Self-Watering Different From Manual Watering?

When watering plants by hand, you always run the risk of watering too little or too much. If you provide shallow watering (frequent, small amounts of water applied to the surface), you run the risk of having thirsty plants.

This method of watering also prevents plants from forming deep, healthy root systems because the water they find is always near the surface of the soil.

Manual, deep watering is another option, but it also comes with issues. When you water plants deeply and infrequently, you run the risk of over-watering and causing root rot. [source]

With SIP just the right amount of water is always available and is delivered from beneath the plant rather than from above. Using a sub-irrigation system to provide water ensures that plants develop deep, healthy roots.

Another advantage of the self-watering planter system is nutrient retention. When watering plants in the garden or in traditional pots and containers, the water runs through the soil and washes nutrients away.

With a wicking system, the provided nutrients stay in place and available to the plants. Any nutrients that do leak into the water reservoir are taken back up when the “plant drinks.”

Using just the right amount of water is good for the plants and good for the environment. When top-watering plants usually more water is used than the plants need.

Furthermore, water is lost to draining-off and evaporation. With a reservoir and wick system, only the amount needed to keep the growth medium at a constant moisture level.


How Does A Sub-Irrigation Planter Work?

When planting and growing using SIP, you will almost never need to top-water the plants.

Just fill the basin (aka water reservoir or sub-irrigation system) with clean water whenever the water level drops. The water is transported and diffused as needed throughout the plant’s growing medium.

With most styles of self-watering flower pots, the pot containing the plant sits on top of the removable reservoir, and the bottom of the pot does not touch the water.

A wick is threaded through the holes in the bottom of the pot, and draws water into the soil at a steady rate through “capillary action.”

Capillary action is defined as the ability of a liquid to move through soil or other materials. [source]

To get the capillary action started, the soil must be “primed” by giving the plant a good top-watering at the outset. Allow excess water to flow through to the reservoir. From then on, only add water to the reservoir.

With most of these planters, you check the water level by looking into the “viewing lip” of the reservoir. Some have a “viewing window“ that allows you to see the water level in the reservoir.

simulation of how sub irrigation or self watering plants work

Some brands of SIP have water indicators that stick up from the surface of the potting medium. This is handy if the plants are set up in a way that makes it difficult to see the actual water level.

With some larger planters, the water in the reservoir is not held in a separate saucer. Instead, it is separated preventing the root ball from sitting in the water.

In this type of planter, a small portion of the potting soil extends into the reservoir and the soil, itself, acts as a wick. The tank is refilled through a tube or PVC pipe that runs from the top of the pot to the bottom.

You can check the water level through the use of a gauge or by observing a viewing window.


Which Plants Thrive In Self-Watering Containers?

Generally speaking, any plant that likes consistently moist soil will do well in sub-irrigated planters. The planters were designed initially for vegetable gardening, but herbs, flowers, houseplants and even orchids can do well. It all depends upon the style of planter chosen and the substrate you use.

For example, orchids do not actually like consistently moist soil, but they can do well in a SIP when planted in a porous substrate (e.g. LECA) and provided an alteration in watering schedule as described here:

How To Water Orchids In Self-watering Planters

Here are a few examples of excellent plant choices suitable for SIP planting:

Compact Veggies

Anything that does well in a raised bed garden has the potential to do well in a SIP. Use common sense and select big enough containers and plants that are unlikely to outgrow them. Some good choices include:

  • Cherry tomatoes
  • Carrots
  • Cabbage
  • Garlic
  • Herbs
  • Lettuce

Houseplants & Tropicals

Any indoor plant or tropical that prefers consistently moist soil will do well in a SIP. Some examples include:

Perennial Plants

  • Hosta plants provide lush greenery for shady spots. (USDA zones 3-8)
  • Japanese Iris produces gorgeous colorful blooms in large planters. (USDA zones 5-9)

Annual Plants

  • Lobelia provides lots of pretty blossoms in sunny locations from springtime through autumn.
  • Snowy Meadow Foam is a pretty choice for hanging containers because of its trailing habits and frothy, white blossoms.
  • Petunias and Pansies are notoriously thirsty flowering annuals that do very well in self-watering hanging baskets or planters.

Planting Petunia in an innovative Self Watering Hanging Basket

There are many other types of plants that thrive when kept in a self-watering container. The key to success in any kind of gardening is to check a plant’s requirements for water, light, and fertilizer before making any purchase.

Then you can determine whether or not you will be able to accommodate the plant and make arrangements for it as needed.


7 Top Choices In Self-Watering Planters

Here is a quick run-down on seven of the most popular brands:

Earth Box’s Terra Cotta Garden

Earth Box’s Terra Cotta Garden kit is a high-quality sub-irrigation planter with a classic look. This large, sturdy, rectangular plastic planter box comes with a wealth of accessories and supplies to help you get your veggie or flower garden set up within minutes of opening the box. Choose from green or classic terra cotta.

Bloem Lucca Planter

Bloem Lucca planter (10”) is a durable option made entirely of recycled plastic. It is available in a lovely shade of French blue.

Lechuza Planters

Lechuza planter’s windowsill SIP is a sleek, rectangular planter made of very durable plastic with a good-looking matte finish. It features a 2-quart reservoir that can keep your plants well supplied for an extended period of time. It is available in white, taupe, charcoal and brown.

Aquaphoric

Window Garden Aquaphoric 7” Self-Watering Planter is an excellent choice for small plants such as windowsill herbs or African Violets. This little planter is available in seven colors.

Mr. Stacky

Mr. Stacky, Vertical Terracotta Stacking Planter Set is a three-tiered arrangement that gives you enough space to plant 12 smaller plants, such as herbs and strawberries in a small space.

Each stack has its own reservoir, and a conversion kit is included that allows you to set up a timer and pump for automatic watering if you plan to be away for a long time.

Misco

Misco 11.5” Flare SIP is a big, no-nonsense planter that can accommodate large plants or small trees. It is available in an attractively speckled shade of off-white.

Mayne Fairfield

Mayne Fairfield’s 20” SIP is a large, square planter that is great for a patio setting. It is made in the US of durable, recycled plastic styled to resemble wood. It is available in black, white or terra-cotta.


What About DIY Self-Watering Plant Containers?

If you are handy, you can certainly make your own SIPs. There are lots of easy and popular concepts you can find online.

Among them are ideas for using a five gallon bucket, innovative ways of using a soda bottle as a reservoir and many more. Here are a couple of good videos that clearly show how to make a bucket-style SIP and a model similar to the popular Earth Box.

Here’s a clever idea using a large planter without drainage holes. USe the idea and adapt it for use with a 5-gallon bucket.

5 minute DIY Self Watering Container Garden

Here’s an interesting video showing how to make your own “earth-box” and provides information on planting.

Making An Earthbox


How to Choose The Best Self-Watering Planter To Suit Your Needs

Clearly, there are many choices in size, shape, and design to choose from when SIP shopping. Some are traditional and not distinguishable from a regular pot or container.

These simple versions typically have a removable reservoir and are available in many colors.

Take care when selecting size. Remember, smaller planters will naturally need to have their reservoirs topped off more frequently than larger ones.

Typically, a small SIP will need to have the reservoir filled once a week. A large one may be able to get by with seasonal watering (every three months or so).

You should also think about what you will plant and determine just how thirsty the plants you are considering truly are.

Square, rectangular and window boxes allow homeowners to get just the right shape of the container to fit on:

  • A deck rail
  • A windowsill
  • A corner or other more angular setting.

These planters come in many different designs and are often so realistically wood-grained that you cannot (at a glance) distinguish them from high-end wooden planters.

The difference is that these tough resin or plastic planters are much more durable and long-lasting than their wooden counterparts.

There are also SIPs (e.g. Earth Box) that come equipped with a mulch cover which shields the surface of the soil, preventing evaporation from the reservoir.

This cover also protects outdoor SIPs from taking in too much water when it rains. This helps keep granular time-release fertilizer from becoming too wet.

If you add dry fertilizer and it becomes saturated, it will release the nutrients quickly and burn your plant’s roots.


How Do You Add Fertilizer To A Self-Watering Planter?

One downside to using SIPs is that mineral salts build up in growing medium. This happens because water is constantly drawn up from beneath and salts are never leached from the soil.

Every time your plant takes a drink, more minerals are added to the potting medium. After a while, this build-up of minerals becomes toxic.

With the exception of distilled water, minerals are present in all water. This is especially true of well water and water that has been put through a water softener.

In fact, do not use softened water to water your plants because it very likely contains high amounts of salt. [source]

Another thing that can introduce excessive amounts of minerals to the planting medium is water soluble fertilizer. Even though it is convenient to use commercial fertilizer, this is not advisable when using SIPs for the reasons mentioned above.

Instead, use a special fertilizer designed for use with SIPs. Some was probably included in the purchase of your container. If not, mix a half dose of granular slow-release fertilizer into the potting medium when you pot your plants.

Alternately, if there is a lot of soil surface area, you can sprinkle granular fertilizer over the surface, very lightly at the time of planting. After this point, do not add fertilizer to the soil or to the water in the reservoir. Doing either will cause mineral buildup.

If you plan to add granular fertilizer at the time of planting, be sure to choose a type formulated for the plants you’re growing. Understand that veggies, herbs, flowers and houseplants have varying nutritional requirements. Fertilize carefully and sparingly.

Do This To Wash Away Excess Minerals

Once a year, during the hottest, driest weather, give your plant a good top watering using collected rainwater or plain water that has been allowed to stand for 24 hours so that chemicals can evaporate.

In a SIP with a removable reservoir, remove the reservoir and water slowly until the plant is drenched and water runs out the holes in the bottom of the pot. This will flush out mineral buildup.

If you cannot remove the reservoir, tip the plant onto its side after watering to allow the excess water to run out of the reservoir. You don’t want the plant to “use” the water being flushed through the soil because it is filled with minerals.

It is advised to repot the plant every year to give it fresh, new soil not full of excessive mineral content.

You can throw the old soil into your compost heap to be mixed in and rejuvenated, or flush it with water to remove excess minerals and then mix it with fresh compost to reuse it right away.


Nutrient Rich Potting Soil Reduces the Need For Fertilizer

Using a growing medium containing lots of natural, organic, homemade compost is a good idea for many reasons.

For one, compost made from:

… and the like has a wide variety of nutrients, along with a host of beneficial microorganisms essential to thriving plants.

Store-bought compost usually consists of one or two fairly homogenized ingredients (e.g. wood shavings and/or manure) and cannot compete with compost you make at home.

If you live in an apartment and don’t have a yard (much less leaves and lawn clippings) don’t despair!

You can compost your kitchen scraps and clean paper waste (e.g. cardboard paper towel rolls, shredded newspaper, coffee filters and other clean paper products) in a small compost bin or with the help of red wiggler worms in a handy, compact worm composter. [source]

What Is The Best Potting Soil For Use With Self Watering Containers?

Because SIPs rely on capillary action to deliver moisture from the reservoir to the planting medium, ordinary garden soil will not work.

It is far too dense for use in a SIP or any other planter. It becomes compacted easily and does not allow the even distribution of water.

Instead, use a well-aerated, light potting medium that allows both air and moisture to circulate freely.

You can purchase potting soil specially prepared for use with self-watering planters. It is smarter and more affordable to make your own, using your own kitchen, yard and/or garden compost.

Here’s how:

You’ll need:

In a large bucket or tub, mix together four parts peat moss or coco coir and four parts aged compost. Add in one part perlite or LECA to help lighten the potting mix.

For every five gallons of mix, stir in a cup of agricultural lime. Water the mixture thoroughly and allow it to soak for about half an hour before using it in a sub-irrigation planter.

Wait a minute! What is LECA?

Light Expanded Clay Aggregate (LECA) sometimes called “clay pellets” or “clay pebbles.“ This product is very durable and strong. It is used as a growth medium in hydroponic gardening and for plants such as orchids. It is very porous with excellent free-draining qualities.

This pH neutral substrate can be cleaned and reused. Use LECA indoors or outdoors. To add lightness and aeration capabilities to heavy soils use it directly in the garden or in all sorts of pots, planters, and containers.

LECA has the ability to both enhance drainage when too much water is present and assist with water retention during dry spells.

Use LECA to line the bottom of planters of all kinds. It helps with drainage, and in some cases, provide a natural water reservoir in the bottom of a closed container.

For example, some SIPs designed specifically for poinsettias are meant to be lined with LECA on the bottom and sides to provide aeration and support for the plant in its original root ball. [source]

Using LECA in this way also provides good root insulation for container plants kept outdoors in cool weather.


3 Tips For Self-Watering Planter Success

#1 – Remember to top up the reservoir regularly. If it runs dry, the soil will dry rapidly. If this happens, it will not be able to wick water when adding it to the reservoir. You will need to start all over again by drenching the plant with top-watering.

#2 – Remember to empty reservoirs in unused outdoor SIPs before freezing weather comes. If the water in the reservoir freezes, it will expand and break the container.

It’s best to empty, clean and store SIPs indoors during cold weather. Simply invert them and keep the planters in a sheltered outdoor area.

#3 – Keep newly planted SIPs lightly watered until you see that water is disappearing from the reservoir.

Regular top-watering primes the soil so that capillary action can take place and draw water from the reservoir.


Enjoy Carefree Gardening, Year-Round, Indoors or Outdoors!

Clearly, self-watering planters can save a great deal of time and hassle. With a traditional garden you must water frequently and keep up with a lot of troublesome tasks.

With a standard planter, you must beware of over-watering or under-watering. Self-watering planters take the guesswork out of watering and a great option for busy people with limited space and even limited gardening abilities.

When you purchase high quality, well-made, carefully chosen, self-watering planters, to create your indoor, patio or poolside garden, you can count on years of good use, and enjoy seemingly effortless gardening success.

Sub-Irrigation planters (SIP) takes the headaches out of watering plants. ideally suited for busy individuals and those who kill plants by overwatering.