What are Nutrients
Nutrients are food for a plant, they help it to grow and nourish it throughout its life. The 3 main nutrients are, Nitrogen, Phosphorus and Potassium, plants will also however require various other trace elements and metals for good growth. As nutrients are also salts they need to be applied carefully and as directed on the packet. Too much salt will make plants ill and eventually kill them.

Choosing a Nutrient
There are lots of ready made plant nutrients on the market some aimed at cannabis and some not. In the end there's not that much difference between them. The more expensive feeds do contain elements superior to that of regular feeds but their use is not essential. As long as the nutrients are 'complete' and given in the correct dosage results should be good.

Complete Nutrients
A complete nutrient solution contains all the nutrients, trace elements, metals and minerals a plant needs for good growth. Most nutrients mixes aimed at cannabis growing are complete nutrients and come in various blends for use with different growing mediums. Hydroponic feeds have to be complete nutrients as they provide everything for the plant.

Nutrients Aimed at Cannabis
There are quite a few benefits to using nutrients aimed at cannabis. They will usually come with helpful instructions about when and how to feed and will also have been mixed with cannabis growth in mind. A general "fed-all" nutrient may be adequate but using a nutrient designed for the purpose will often make life easier for you and the plant.

N.P.K.
Nutrients have an N.P.K. ratio on the packet. This shows the amount of Nitrogen (N, The leaf maker), Phosphorus (P, The root maker) and Potassium (K, The flower maker) the nutrient contains as a percentage. A complete fertiliser will also contain all the other nutrients and minerals a plant needs for good growth but may not always list them.

Nutrients Cannabis Likes
Cannabis is a nitrogen lover and whilst in its growing stage it will need a feed containing extra nitrogen. Once flowering starts properly however its need for nitrogen lessens and it requires a feed with extra phosphorus and potassium instead. As cannabis finishes flowering and matures its need for all nutrients gradually decreases. This is why a lot of ready made cannabis nutrients come in two or even three stage formulas.

Growing and Flowering Feeds
Unless instructed otherwise don`t change to a flowering feed as soon as you change to a flowering light cycle. Plants take time to respond to light changes and will continue to require the extra nitrogen missing in most flowering feeds until growth has slowed and flowering begun. This usually take around 2 or 3 weeks.

Mixing Nutrients Yourself
Leave this to the experts. You can end up with all sorts of problems mixing nutrients yourself or using two or more incompatible feeds at the same time. If the nutrient you are using isn`t up to the job choose another rather than trying to mix it with another to boost its performance.

Nutrients in the Medium
To easily control the rate and amount of nutrients a plant receives use bland nutrient free mediums, with or without standard potting compost mixed in. Then add a soluble complete feed to the plants water in the recommended amounts. Mixing manure's or slow releasing elements with a plants medium can lead to trouble unless you are experienced.

Organic Nutrients
Thankfully there are now more and more ready made organic feeds available. Use these if you want to grow organic and have little or no horticultural experience. Mixing up organic feeds yourself takes time and knowledge. Getting a good, safe, balanced home-made mix for plants can take months.

Using Nutrients
Less is better so start with 1/4 strength feed max. for cuttings or seedlings. Gradually increase this as the plant grows taking into account the intensity of light it is receiving. The more intense the light the more nutrients the plant will require. If you are using circulating tanks of nutrient solution change them completely every 2- 4 weeks to ensure a balanced nutrient solution. A change in feeding will take 3 days to 2 weeks to show through in new growth so be patient.

Nutrient Problems
Plants being fed as directed with a reputable feed should not suffer badly with nutrient problems. Therefore if plants begin to look unwell check elsewhere before blaming or adjusting the nutrient. Incorrect pH of the medium, nutrient solution or water will restrict nutrient uptake so test these to see if they are acceptable. (Test the solution after it has been through the growing medium to get a better idea of the levels the plant roots are actually dealing with) Meter users should also make sure their meters are calibrated correctly. Over-watering is another culprit for sick looking plants. Let soil dry a little between watering or feeding to allow the roots to breathe. Overfeeding or nutrient build up in the growing medium will also make plants sick and is easily done even by experienced gardeners when using pots. Other things to check for include pests, disease, fungus, temperature or lack of light.

Signs of Underfeeding
If you are using a complete feed correctly the only deficiency your plants may still suffer from is nitrogen deficiency. Look for purple tinges on the leaf stems or main stems and a general paling of the plant as a whole. Using a complete nutrient high in nitrogen increase the feed strength or frequency and look for good colour on new growth as older leaves may never fully recover.

Signs of Overfeeding
Very dark green foliage or leaves that twist, spiral or fold in on themselves are a sign of overfeeding. If continued plants begin to wilt and die as they loose water to the salty nutrient. Remedy by flushing the plants growing medium with lots of plain pH balanced water. Test the water after it has been through the medium and continue flushing until TDS levels are acceptable. Begin feeding again only when healthy new growth appears using a reduced strength or frequency of feeds.

Flushing Nutrients
Whatever nutrient you use you should always stop feeding at least 10 days before harvest. Only give plants pH balanced water from then on. Doing this will help "flush" the nutrients out the plant and produce better tasting and better burning buds.