I keep a few of my indoor sowings under the stairs.

A lot is going on in my pre-planting section indoors right now. The grow lights are not quite enough now and I started moving large troughs of plants to my south-facing window. The natural light is usually enough at the start of April. All I can do is to cross my fingers!

It's time to start fertilizing when the indoor plants have grown a little bit. I do this to give the plants an extra boost of energy to grow in their often quite small pots.

There are not a lot of nutrients in regular potting soil. When I re-plant the plants, I put them in more nutrient-rich soil. But believe me, many plants grow very fast indoors where it's nice and warm. And then all of a sudden, there are no nutrients left. It happens a lot faster than you might think. So, I always make sure to fertilize all of my plants indoors so they can grow nicely before it's time to take them outside.

Read more about diluted urine here: Using diluted urine as fertilizer

What, how and when?

I always water the indoor plants with liquid fertilizer about a week after I replant them in larger pots. In some cases, I need to water them before replanting too. I don't really have a particular fertilizing schedule. Instead, I just do it wherever there's a need.

A lot of people wonder what I use as fertilizer, how much and how often.

I fertilize with diluted urine and leachate from my bokashi compost. I will write more about this subject shortly. Believe it or not, urine is actually the perfect fertilizer. It contains everything that the plants need. For example nitrogen, fosfor and potassium. The very same things that you get in store-bought fertilizer. But urine is of course completely free! The plants absorb the fertilizer very easily, and the results are visible quickly. For anyone who wants a cheap and simple solution for their fertilizing, this is really the way to go. Start early when the leaves start to grow.

Some of you might think it sounds really odd to fertilize with diluted urine indoors, especially since you want to eat these plants later. I will get back to this shortly.

Dilute the urine

The urine you use to fertilize your plants should always be diluted. The more water you use, the less concentrated it will of course be and this also means it smells a lot less indoors. Some studies show that it's better for vegetables, flowers and regular potted plants to get fertilized often with a less concentrated solution rather than using a stronger mix more seldom.

They usually say that you should use one part urine and ten parts water, but if you want to fertilize with diluted urine indoors, I think one part urine and twenty parts water would be better. And make sure to water often. I do it around every three watering indoors. This really helps the plants grow quickly!

Vegetables that need nutrient-rich soil

• Cabbage
• Eggplant
• Celery root
• Leek
• Artichokes
• Tomatoes
• Bell peppers

How do we do it?

We have a potty in the bathroom and our younger kids use it. I fill it with water right after someone used it and then I pour the fluid in a watering can or a plastic bottle, and water my plants straight away.

I sometimes use the potty myself too. We use a combined potty/watering can later in the season, but I don't need that much fertilizer indoors that I need to put it in my bathroom permanently. There's a watering can in my polytunnel right now that I have started peeing in when I'm outside, and then I use the diluted urine to fertilize my beds. I will write more about this later.

If you don't have kids, you can of course pee in a little bucket or plastic tub once a day and water your potted plants and indoor vegetables and flowers with that.

Fertilizing tips

• Water a little bit at a time so the fluid doesn't pool on the plate underneath your pot
• Don't fertilize plants on a heat mat
• Don't fertilize self-watering troughs
• Don't leave the diluted urine outside before you use it
• Avoid using fertilizer on the leaves

Cabbage needs a lot of nutrients and grows nicely if you fertilize with diluted urine.

Three common questions

Does it smell? No, not as long as you dilute the urine properly, make sure that the urine is not old or gets warmed up by a heat mat or similar. I don't think that anyone who comes to visit us think that it smells even though I water my plants with diluted urine every day.

Can you use this method if you are on medication? This is something that people should decide for themselves. There are some studies on the subject and overall, it seems to be ok to use it as fertilizer, as long as you don't use very unusual medicines.

Can you use too much fertilizer? The plants you grow indoors are more sensitive than the large plants that grow outside in plenty of soil that can take care of the nutrients. If you use too much fertilizer, the plants might die. So try to be a bit careful. Or, why not fertilize a bit more than you think you need just to see what works and doesn't?

For the beginner

• Try watering plants that you are going to eat later in the season, if you feel a bit worried about the hygiene.
• Don't tell your family that you have tried fertilizing with urine
• Pee in a little container that you can throw away directly if you don't want to clean it
• Keep a dish brush you can use for your potty in the bathroom
• Use a mild soap to clean the potty

Fertilizing with diluted urine might be a bit controversial. Many think it's a bit yucky. This knee-jerk reaction might also come about because we aren't used to dealing with our own pee. But you should try going against that first impulse to push it away because it really is a great fertilizer! I feel like this is a great resource to use both outside and indoors. I actually think I need it indoors the most since I can't mulch or use compost inside.

Every time I write about that I fertilize with diluted urine, I get some nasty comments that might scare other gardeners. These comments are mostly built on what people believe rather than actual facts. If you want to write about how using diluted urine is dangerous or bad, I want you to really research the subject and find reliable sources that support your claims. I will be happy to discuss it if you do your research.

So, if you want to fertilize with diluted urine my advice is to just go for it! I think you will see the results really quickly. Good luck!
/Sara Bäckmo