From the manufacturers website:
Flower Burst is a unique new product from Buddhas Tree that has been specifically created for use during your plants pre-flowering and early flowering stage. It promotes an explosive flower set without hindering continuing vegetive growth, creates an increased number of flower sites and ensures a seamless change into the pure flowering phase of the bloom cycle in a way that more closely matches your plants needs. This results in a quicker and much more efficient flowering response. which is achieved in the kindest and safest way with a carefully composed blend that uses the same highest quality raw food safe materials that made our best selling PK 9-18 such a success.
When the photoperiod is reduced to induce the flowering response, it may seem to some growers early on that it is the beginning of a dormant period for your plants whilst you wait patiently for flowers to appear. In reality, it begins an important transitional time for your plants, both externally and internally, where many changes will take place. As we know, when these changes from vegetive to flowering growth occur, your plants nutritional needs also begin to change, hence why base nutrients are made with a separate `Grow` and `Bloom` formula to loosely reflect this changing demand. But when is the right time to change from one to the other?
When it comes to the first few weeks of early flowering the plants are in a cross over phase where their needs are different from what it is possible to give them from just a single `Grow` or a `Bloom` base nutrient. During this time your plants are doing many things. They are still busy with vegetive growth above the ground, increasing secondary leaf production, building branches and increasing the number of internodes that will eventually form the structure of your flowers and fruit. The leading element for healthy vegetive growth is Nitrogen and this is reflected in a `Grow` nutrients NPK ratio with a high N ratio and low P(Phosphorus) and K(Potassium). This sudden increase in vegetive growth during the first weeks of pre-flowering is the reason that a lot of growers keep their plants on `Grow` nutrient for the first week or so of their bloom cycle, as they know that the Nitrogen content of a `Bloom` nutrient is often not enough to maximise the plants vegetive growth spurt at this time, But herein lies an issue.
There are also huge, equally important changes happening below in the root zone that you cant see, where your plants are accelerating their production of roots so that they will be able to maximise nutrient uptake during the later most productive and demanding phase of the flowering cycle. The most important element in this phase of vigorous root growth is Phosphorus. So whilst a `Grow` nutrient ensures healthy and speedy above-ground growth it hasnt the necessary Phosphorus type and amount to maximise the below-ground root growth essential for maximum flower production.