additives are necessary during the flowering or fruiting phase of a plant.
A variety of flowering additives are available, however PK additives are
the most common type.
additives primarily contain phosphate (“P”) and potassium (“K”). These
elements are essential during the flowering and fruiting phase. Although
bloom nutrients contain phosphorus and potassium, heavy fruiting plants
such as tomatoes and peppers have an especially high demand for these
PK additives are used in conjunction with bloom nutrients
to help ensure no deficiencies occur*. They are also a more economical
alternative compared to using extra bloom nutrient.
*Note that EC readings will not help determine if sufficient potassium and
phosphorus is in reserve.
additives should generally be used from the onset of budding until flowers
or fruit are fully formed.
When choosing a PK additive choose a brand that is relatively pH
'neutral'. Many brands are quite ‘alkaline’ which causes a significant
increase in nutrient solution pH. These can quickly destabilize the
nutrient if pH is not adjusted immediately after dosing.
Organic plant-growth-regulators such as auxins, gibberellins and cytokinins are also useful components of flowering additives. These help
promote fruit set and growth (see “PGR” section).