When To Start Feeding Your Seedling

If you’re a newer grower, you may have trouble figuring out the best time to start your first feeds – it’s totally normal. The truth is that seedlings can chug along with very little nutrients for quite a while before showing any obvious symptoms of a problem, but that doesn’t necessarily mean you couldn’t be doing more to kickstart your plant’s transition into the vegetative phase.

Soil vs inert mediums

Soil growers: you don’t really need to worry about this too much, as your plants will likely only require additional feeds once they’re well into their vegetative phase. Most good soil mixes in South Africa (Atami, Freedom Farms, Orgasoilux, Organics Matters, etc) can go in a solo cup for a couple of weeks before needing a feed, while 5-10L pots tend to provide the first 3 weeks of growth, given some margin of error.

That said, it’s always worth knowing what is actually in your soil rather than assuming a particular pot size automatically means a certain amount of nutrition. Some mixes are much heavier than others, and this can make a big difference to how quickly your plant starts using up the available nutrients.

However, those growing in inert mediums like coco or rockwool have to carefully balance their nutrient loads in the early stages of growth. Unlike a good amended soil, the medium itself isn’t providing much in the way of nutrition, so you’re much more directly responsible for supplying what the plant needs.

Too much, too quickly, and you will stunt the plant and maybe even burn it. Wait too long, and you’ve missed days of potential growth due to a lack of plant fuel.

So, when should you start feeding them, and how much should you give?

Starting your first feeds

If you’re growing in an inert medium, I recommend introducing a light feed once the first true leaves (the serrated ones) have developed and the seedling is clearly established. This typically takes about 3 to 5 days after the seedling has emerged, although I’d pay more attention to the plant than the exact number of days.

The important thing here is to start low. A small amount of nutrition can encourage early root development and set the plant up for a gradual increase in growth speed, rather than hitting it all at once with a full veg feed.

Personally, I use roughly 25% of the full vegetative solution for the first week, and then 50% for the second, and by the start of the third week, I’ve typically moved to full feed.

One of the reasons growers often underfeed during the first 2 weeks is because the plants don’t show any obvious signs of problems at moderate nitrogen rates. But there is often a sacrifice in growth rate being made, as even young plants can grow very quickly when they have access to a nitrogen-rich medium with good watering and light practices.

You also don’t want to confuse slow growth with a nutrient deficiency. If your seedling is struggling because of poor light, overwatering, cold temperatures, damaged roots or another environmental issue, adding more nutrients isn’t going to fix the underlying problem. In fact, it can make things worse.

Knowing when to cut back

The easiest way to tell whether you’re pushing the feed too hard is to pay attention to the colour and shape of the leaves, particularly the newer growth.

Feeding high nitrogen too early can cause shiny, dark green leaves and some clawing. If you see that, cut back your feeds a bit until the new growth is back to being vibrant and then readjust.

The goal isn’t to give a seedling as much food as possible, it’s to give it enough to keep growing quickly without creating another problem in the process.

As your plant establishes itself and starts putting on more growth, you can gradually increase the nutrient strength until you reach your normal vegetative feed. There’s no real benefit in rushing this process. A gradual increase gives you plenty of room to react to what the plant is telling you, rather than trying to fix a problem after you’ve already overdone it.