Why is rainwater good for my plants?

I often read post on social media asking if rain water is really that good for their plants and if there is a difference.  Before I was able to collect rainwater for my plants, I didn't know what I was missing. Now that I have experienced it, it really hard to go back. There really isn't anything better than rainwater. Let's look at some of the benefits. 

It is significantly less harsh than tap water.
Rain water is considered to be "soft" compared to tap water, which is generally "hard". Soft water means it is free from any additives (e.g. salt, minerals), chemical and/or pharmaceuticals often found in municipal water. When hard water is used, salt and chemicals will build up in the soil over time and will be tough on plants. When plants are potted, the accumulation of these minerals are more concreted which is why it is recommended to flush out your soil with rainwater or softer water to keep the pH level balanced.

If you collect rainwater in any sort of container (like a bucket), the rainwater  will have traces of organic materials. Though rainwater is clean (and should run clear), when it ends up in your container(s), it has already been exposed to materials found on rooftops such as leaf litter, pollen and/or bird droppings, which is great for your plants. These are all beneficial to plants which has a similar effect to you lightly fertilizing your plants.

Rainwater is more acidic.
Rainwater is naturally more acidic. Plants often prefer soil pH level to be between 5.5 and 6.5 (pH 7 is neutral); which is exactly the pH range of rainwater. Tap water is more alkaline in order to prevent pipes from corroding and can have a pH level of 8.5 and upwards. Why is pH level important? It helps determine what nutrients are available to your plants.               

 

Plants need nitrates in order to thrive, which is found in nitrogen. Nitrogen helps in the development of foliage. Nitrates is a combination of nitrogen and oxygen molecules. 

Once you give your plants a good drink of rainwater, you will notice that the leaves will have a nice shine to them compared to those that are grown indoors and only receive tap water.

Below are before and after images of succulents that were left outdoors and watered with rain water.

Though the "stress colours" may be gone or faded, the overall health of the plant has improved dramatically.