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What is a SIP PlanterWhat is a SIP Planter?

If you have a patio or container garden with traditional pots or outdoor planters, you know it takes a lot of work to maintain your plants, particularly during hot seasons. In the middle of the summer, you’ll need to water your plants at least daily and apply fertilizer regularly for them to survive. Also, if you’re not good with potted plants, you’re likely to kill them through overwatering and overfertilizing. Instead, you can create a flourishing container garden using a sub-irrigated planter (SIP), which is great for planting flowers, veggies, and herbs on your deck, balcony, or patio. A SIP planter is ideal for busy individuals and those who are poor in plant care. In this post, we’ll cover more on SIP planters to help you understand their types, benefits, workings, and more.


A sub-irrigated planter is a container with a sub-surface water chamber to provide irrigation. In this case, water wicks up to the roots via capillary action rather than from the container’s surface, like in traditional pots. They are sometimes also called self-watering window boxes and planters since they work by allowing you to overwater a planter and water less frequently. Unlike regular planters and pots, SIP planters sometimes don’t have holes at the bottom surface for draining excess water. The holes help prevent root rot, but they also contribute to nutrient loss due to constant water flushes through the soil. This is one of the reasons SIP planters make great options. This type of planter makes sense because, naturally, plants absorb water from the roots upwards. SIP planters have been used for decades to hydrate plants and create successful gardens for flowers and foods.

How SIP Planters Work

SIP planters may take various forms and designs and can be designed for indoor or outdoor use. The basic structure of the planter features several components, including.

Water-tight container: This can be a box lined with a pond liner or a plastic container for holding the potting mix
Growth medium: You can use potting mix or soil with the right ingredients to oxygenate and provide plant nutrients. If you use soil, it should be lightweight instead of dense.
Filling tube: This tube is usually on the planter's side and is used to add water or liquid fertilizer to the reservoir. Perforated aeration screen: The plant roots need oxygen, so this screen features holes for ample oxygenation. It also holds the potting mix and the plant above the water level.
Wicking medium: At the bottom of the planter, there’s a wicking medium, which can be a cord, cloth, or porous basket. Some wicking reservoir systems are also available for purchase online.
An overflow drain outlet: Near the bottom, there’s a drainage outlet for removing excess water from the reservoir. As noted, the water reservoir or chamber is usually at the bottom, and it’s useful for holding water. The reservoir can be removable or non-removable, depending on the design of the planter. Above the water reservoir, there’s an air chamber, which prevents anaerobic conditions. So basically, the growth medium is on top, while the water is underneath, and there’s an air gap or chamber in the middle. The growth medium gets moisture via the wicking medium through capillary action. As long as there is adequate water in the reservoir, the growth medium will self-regulate to ensure an even and consistent moisture level.

SIP Planters vs. Regular Containers

Patio and indoor plants are only great if they thrive and add a green touch to your space. More importantly, they should thrive with minimum effort and survive hot summer seasons without drying up. With that in mind, choosing between SIP planters and regular containers shouldn’t be difficult.

Regular Containers
Traditional containers and pots get the job done, but they need a little more work and regular attention. You’ll need to water your plants weekly and fertilize them regularly to ensure they survive. The watering frequency tends to increase during the hot seasons. With regular pots, there’s also the risk of overwatering or underwatering, which eventually causes your plants to die. Overwatering causes root rot and faster depreciation of soil nutrients, while underwatering results in thirsty plants and poor root systems.

SIP Planters
On the other hand, SIP planters feature a water reservoir, which reduces watering frequency by up to 3 to 5 times. So, if you’re used to watering weekly, a SIP container can be an excellent option for minimizing regular plant care and conserving water in your home. The use of the reservoir and wick system keeps the potting mix or soil at a constant moisture level, as long as there’s water in the chamber. Since irrigation occurs through capillary action, nutrient loss is minimized, allowing plants to flourish well in indoor or shaded areas.

Benefits of SIP Planters

Compared to traditional pots, SIP planters offer different advantages that make them perfect for gardeners, growers, or homeowners who need to add flowers or vegetables to their homes. Here are key benefits you need to know.

1. Minimized Plant Care
SIP planters minimize plant watering by up to five times, making it ideal for people with busy schedules. Optimal nutrient retention also means a reduced need for regular fertilizing. This reduces routine maintenance, especially if you live in dry climates and have many potted plants. Consequently, the planter offers an easy-to-follow and predictable routine for plant care. You can go on a long trip or vacation without worrying about your plants. More importantly, you can cut your water usage by over 50% compared to conventional top-watering practices.

2. Offers Consistency
Self-watering planters ensure plants get the amount of water they require. The wicking system means capillary action occurs based on the moisture level of the growth media and the plant’s root network. As such, as long as there’s water in the chamber, the plant will consume only what it needs to flourish, ensuring consistent growth with simple care. This way, you remove the guesswork from plant care, particularly if you’re always struggling to determine the amount of water your plants need.

3. Simple and Flexible Solutions
You can add a simple garden anywhere you want with a self-watering planter or box, including your windows. For example, we offer a patented window box water reservoir that allows you to convert window boxes into stunning planters. This flexibility means you can add plants wherever you like to improve the appeal of your home. Plus, it’s not as complicated as automated systems, which feature lots of tubing and piping and involve the use of electric power.

4. Healthy Root Growth
In traditional pots, both overwatering and underwatering affect the health of a plant’s roots. Underwatering leads to shallow root growth since the roots can easily access water near the topsoil while overwatering leads to root rot. In a SIP planter, the wicking system maintains optimal moisture level all the time, allowing the roots to grow healthily without going deep to find moisture supply. If you have the right planter size for your plant, your plants will always have the right root network to support healthy growth.

5. Nutrient Retention
SIP planters have a closed system, which allows all the nutrients to stay within the planter. Since water is added to the reservoir using a filling tube, the risk of expelling nutrients through the drainage holes or into a garden bed is minimized. As a result, self-watering planters will always have healthy nutrient levels to ensure your plants thrive. If nutrients wash into the water chamber, they’re absorbed back through the capillary action.

6. Reclaim Your Land
If you live in a paved area or land that doesn’t support plant growth, SIP planters make great options for incorporating plants into your space. While paving adds aesthetic appeal to your home, it limits your space for growing food or flowers. SIP planters allow you to set up a simple garden anywhere, including your deck, patio, rooftop, parking lot, or sidewalk. You can grow delicious foods or beautiful flowers regardless of your space.

Picking the Right SIP Planter

It’s essential to note that the success of your patio or container garden depends on the type of planters you choose. SIP planters are designed to ensure your plants flourish with minimal care, but that doesn’t mean they’ll work for every plant. With that in mind, there are several considerations you need to take into account whenever you’re buying a SIP planter.

I. Plant Type
You need to pay attention to the plants you want to grow and their water consumption needs. SIP planters are ideal for annual vegetables and plants like kale, carrots, squash, corn, peppers, tomatoes, and lettuce. Plants with more extensive roots will definitely need large pots. Note that perennial fruits and herbs are not ideal for these planters. During cold seasons, plants depend on hardiness to survive through temperate weather. Since SIP plants are above the ground, where it gets really cold, hardiness is reduced, leading plants to die.
II. Shape & Size
If you want a specific layout or design for your container garden, it’s vital to pick the ideal shape and size, like square, rectangular, window, or round planters. For example, a rectangular planter is suitable if you want to add a window box. Or, you can get one that suits your deck rail, window sill, corner spots, or other angular settings. Regarding size, smaller pots will need you to top up the reservoir more frequently, and they can’t support healthy root growth for some plants. Consider getting a planter with a large reservoir to minimize regular watering and support profound root growth for specific plants.
III. Water Capacity
Typical SIP planters have water chambers holding about 2 to 10 gallons. Still, you can find large planters that hold up to 50 gallons of water. As such, it’s vital to consider the water capacity of your desired planter, depending on your plant’s water demands and the number of plants you want to grow in a single planter.
IV. Material
Most self-watering planters are usually made of heavy-grade plastic, which is excellent for withstanding the elements if you want to place your planter outside. PVC Planters are great because they don’t get damaged by water, insects, or soil. Other great materials include treated metal, cedar, and resin, though these options can be more costly and heavy to move than plastic planters. Cedar planters are a great wood choice since the wood natural resists bugs and insects. Generally, aim to pick a material that doesn’t warp, rust, or fade over time.
V. Features
You should also look at other useful features, such as a water level indicator/gauge. The gauge will make it easy for you to know the water level in the reservoir, allowing you to refill it only when necessary. If the pot features a waterproof liner, it should be food-safe and non-leaching, particularly if you want to grow herbs and vegetables.

5 Tips for SIP Planter Gardening

SIP planters are designed to simplify container gardening, but several factors must be considered to ensure successful gardening.

1. Choose the Best Potting Mix SIP planters rely on capillary action for moisture supply to the plants from the reservoir. In this case, ordinary garden soil will not be ideal to use as it’s too dense. Plus, it becomes compacted easily in a pot, inhibiting water distribution. Instead, you need to use a well-aerated growth media that allows ample water and air circulation. There are potting mixes that are specially formulated for SIP planters. Still, you can make your own using garden and kitchen compost. To make your own, you’ll need sphagnum peat moss or coco coir, finished compost, perlite or LECA, and garden lime. Mix four parts coco air, four parts compost, and one part perlite in a bucket. Add one cup of lime and water the mixture thoroughly, then allow it to soak for 30 minutes before using it in your planter.
2. Monitor the Water Chamber Self-watering planters reduce the need for regular watering, but checking the water reservoir is essential to ensure your plant doesn’t dry out. This is particularly important when you’re traveling for an extended people. Planters with a water level indicator make monitoring easy, allowing you to top up the reservoir as needed. If yours don’t have a gauge, you’ll have to check the level manually using a flexible rod and top up.
3. Protect Your Plant and Planter During Winter During the cold season, move your plants indoors before the temperature outside starts freezing. If possible, place your plant near the window to allow it to get enough natural light to grow healthily. If you have unused planters outside, it’s advisable to empty their water reservoirs and keep them indoors during the winter season. If left out and the water in the reservoir freezes, it’s likely to expand and break the reservoir.
4. Water Your Plant Normally Bi-Yearly Just because the SIP planter is a self-watering container doesn’t mean you should completely stop watering your plant normally. In fact, it’s advisable to water your plant normally at least twice a year using rainwater or plain water.
5. Window boxes and railing planters are another option that allows you to not have to bend over to enjoy gardening from your planter. At Flower Window Boxes, we specialize in self-watering window boxes and planters of all shapes and sizes.

Matt-buquoi-author-flower-window-boxesAbout the Author
Matthew Buquoi is the owner of Flower Window Boxes, Inc., which is one of the largest online window box companies in the United States. In addition to being the owner, he is also an expert author, and regularly writes about industry topics in the window boxes, planters, exterior shutters, and home and garden industry.