Fundamentals of Sub-Irrigation
Let's be clear, the reason you're building a SIP Garden is to save water.
By saving water, you save time, while simplifying the growing process. So whether you call it a self-watering garden, a wicking bed, or a sub-irrigated planter, the principle is the same - water from the bottom up.
Instead of watering from the top down with a water wand, sprinkler, or drip irrigation to mimic rain like almost all conventional watering systems - remember that rain is fickle and prone to drought! With a SIP garden, you water directly to a hidden reservoir beneath the soil and mimic the consistency of the natural water tables found in all the worlds most bountiful growing environments.
Water the way nature prefers, results are amazing.
The Top Water Exceptions
There's always some exceptions aren't there? Well with SIP Gardens they happen right at the beginning.
- When first installing your soil, make sure that it is thoroughly moist to kick off the capillary action. Dry soil is hydrophobic; meaning it doesn't want to get wet. Think about a sponge, a moist sponge just soaks up everything, whereas a dry sponge just kind of smears liquid around. Make your soil moist like a sponge to kick off the wicking magic!
- Planting/Starting from seed. You need to make sure your plants have time to establish their root systems. If unmulched, it's very normal for the top 2-3 inches of soil to dry out a wicking bed / SIP Garden, so you have to make sure you're plants root systems are thoroughly established down into the wicking zone. So ensure the top of the soil stays moist for at least 1 week after planting established seedlings, and for at least 2 weeks after your seeds sprout and form their first set of true leaves.
- If your reservoir ever dries out entirely, thoroughly water from the top to turn it into that moist sponge again!
How much will I actually have to water my SIP Garden?
It's a good idea to make reservoir checks part of your weekly routine. Often your reservoir will still be quite full, but if your visiting your garden weekly, you'll also be able to do all the harvesting, pruning and maintenance that also play a part in your garden's success.
Throughout the year though, there is going to be some variation. Rain, sun, and where your plants are at during their growth cycle all factor in to how frequent you'll have to water. For example, during July and Aug if you get a heat wave while the tomatoes, cucumbers and other heavily fruiting plants are growing in size, you may find the need to water more than once a week.
In Vancouver, our approximate watering schedule over the last 8 years has been:
- once in April,
- once in May,
- 2 times in June,
- Weekly in July,
- Weekly in Aug,
- 1-2 times in Sept.
- For 12-14 times total per year
Here's a great comparison chart that helps contextualize some watering expectations correlated with weather forecast. It's not perfect, but it gives your a great idea of how frequently you'll be filling your SIP Garden reservoir, and how SIP Gardens stack up to over types gardens:
|SIP Garden||0-1x per month||3-4x per month||4x per month||5x per month||6-8x per month|
|Earth Garden||2x per month||4x per month||5-6x per month||10-12x per month||20-30x per month|