Double The Yield Of Tomatoes, Cucumbers & other Vegetables By Watering Them Immediately With This... As spring gets going, your vegetables will amp up their growth and a dose of liquid fertiliser can do wonders to ensure healthy growth. Unlike granular fertilisers, liquid fertilisers get the nutrients to your plants quickly, so you can feed them when they need it most. When using a solid fertiliser in the garden it can be easy to add too much, which in turn can be detrimental to your plants. Too much nitrogen added to beetroot, for example, will lead to big green tops and not much root.