Last week, I gave you my top 7 tips for designing a passive solar greenhouse. But once you’ve got the greenhouse in place, how do you manage it to get the most out of it? After 5 years of operating one here in the Canadian North, I’ve learned a thing or two about how it’s done. As always, I welcome your thoughts, comments and suggestions!
And if you missed it last week, scroll down to the bottom of this blog to catch my hour-long interview with Diego of the Permaculture Voices podcast on all things passive solar greenhouse related.
Greenhouse Management Tip #1: Get the Watering Down
Watering too much or too little has cascading detrimental effects on your greenhouse’s production. Because greenhouses are artificial environments, you need to pay the utmost attention to watering. Too much water and your plants will drown. Too little water and your plants will get stressed, production will go down, and plant pathogens and pests will attack.
We’re currently growing in wicking beds, which are great because they have a self-draining/irrigating reservoir that helps to regulate soil moisture. In future greenhouses, I also would like to grow in native soil that has been built over time through cover crops, mulch and compost. Soils high in organic matter and biological activity do a lot of water regulation on their own. My main watering strategy in this future greenhouse will be drip irrigation because it’s easy to control.
In addition to water volume, quality is also important. Use rainwater if you can. Municipal water is energy-intense, costs money, and is loaded with chlorine and fluoride. Rainwater is soft, has no additives and is free once the infrastructure is set up. Hard water from the tap is also an issue for drip irrigation; in high evaporative environments it can “salt” the soil over time.
Greenhouse Management Tip #2: Mulch, Mulch, Mulch
Mulch is the number one soil amendment you should add to all your garden beds! Mulch cools the soil surface and eliminates light form hitting the soil surface. This allows underground critters to do their magic right up to the top of the soil surface, and this is how long-term soil carbon is built. In addition, mulch reduces evaporation rates, which reduces the amount of water you need to irrigate the system.
Over time mulch will be consumed by the soil microbes and you will have to add more. Practice constant mulching and watch your plants perk up!
Greenhouse Management Tip #3 Bring in Beneficial Bugs
Because the greenhouse can be hard for insects to find their way in, we have to go the extra mile by planting vibrant and aromatic flowers within the space. Ideally we want plants with small flowers as they tend to be great at attracting beneficial insects, but plant whatever you have. In addition to getting bugs into the space, your greenhouse will look much more lovely when you’re in there managing it. Some flowers we use include alyssums, marigolds, sweet peas and dill.
Greenhouse Management Tip #4: Stay on Top of Diseases
At the first sign of disease, you have to strike! That is not to say we should spray problems away with nasty chemicals, but rather act decisively to get the problem under control. Generally pest and diseases stem from a few situations:
- Soil deficiency
- Too much heat
- Too much humidity
- Not enough air movement, which can lead to issues #2 and #3
We generally take a multi-stepped approach to these issues:
- Deal with the problem plant or pest.
- Address the root cause.
- Monitor and reassess.
For example, if we notice any plant pathogens we remove them from the space. A prime example is powdery mildew – plants that exhibit this disease are pruned to remove the affected portion or are removed entirely. This disease is usually caused by water or heat stress.
For aphids or other similar pests, we vacuum them up and add worm castings to the soil, mulch to the surface, and compost extract to the mulch and leaves. When we catch it early, we can usually avoid future issues – it’s all about being vigilant.
Greenhouse Management Tip #5: Re-mineralize the Soil
Every season we re-mineralize the soil with non water-soluble minerals and worm castings. These slowly get incorporated back into the soil via the fungi and bacteria and are made bioavailable to plants. Poor soil is typically the main reason greenhouses have issues. Get your soil right and everything will fall into place. We also like to cover crop the soil and rotate our crops if possible.
It’s also good to let your greenhouse freeze for a couple of months if that fits within your management plan. This sterilizes many pathogens and ensures that your soil is ready to go by late winter. Of course, this is not possible if you’re growing subtropical plants (bananas, passionfruit) or Mediterranean perennials (olives, pomegranate), so adjust accordingly.
Interested in more tips on managing a thriving passive solar greenhouse?
Check out our design guide and course HERE.