Foliar Spray v. Slow-Release Fertilizer

By Stuart Robinson

There are two ways to feed plants and gardeners are often divided as to which method is the best. Some swear that foliage fertilizer sprays are the most efficient and effective method at delivering nutrients to a plant. Others, especially the permaculture set, are adamant that ground based fertilizers are the better of the two.

Well, it may just be that both are essential. In fact, using both foliar spray and slow-release fertilizers may be an even better outcome for you plants.

We’ve been re-indoctrinated to believe that the soil in which a plant grows is the most important element in our garden’s health. And quite rightly so. However, this has come at a cost because our perceptions of foliar spray fertilizers has become more negative.

We know and understand that plants receive most of their nutrients through their root system. If the soil is healthy and well nourished then the plant can feed well and grow with a minimum of fuss and problems. Even pests and disease are less likely to trouble our plants.

What we may not know is that using foliage fertilizers may actually increase that intake — and exponentially as well. This report explains the process;

By applying a foliar fertilizer directly to the leaf, it increases the activity in the leaf, at the same time increasing chlorophyll and thus photosynthesis. Because of this increased activity, it increases the need for water by the leaf. In turn this increases water uptake by the plants vascular system, which in turn increases the uptake of nutrients from the soil.

So, in actual fact while we need to maintain the nutrients in the soil the use of foliage fertilizers can increase their effectiveness and the plants efficiency at using them.

How to use foliar spray fertilizers

Foliage fertilizers always retail in liquid form, or at least in powder form that requires them to be dissolved in water. This is the best way for your plants to draw their nutrients from the fertiliser.

Most plants will only require a slow-release fertilizer application once at the start of each growing season. However, foliage fertilizers can be applied much more often and this depends on the type of plant grown.

  • Perennials should only require a foliar spray every 6-8 weeks during their flowering or growing season.
  • Annuals are much heavier feeders because their whole growth needs to be completed from seedling to producing plant within one growing season. Therefore, their fertilizing needs are heavier and they will require a foliage fertilizer every 3 weeks at a minimum.
  • Vegetables: On the other hand, veggies need even more and should be fed through their foliage every week during their production season. This will stave off any pest and disease problems and increase the yields of your vegetables.
  • Fruit: If you compare the speed of most fruit trees from flower to produce you will notice that it is considerably slower than say, a carrot crop which can be ready within 12 weeks. Therefore, there is less need for fruit trees to be fertilized and these should be treated the same as your annuals.