When you walk down the aisle in the garden shop, there is often a bewildering selection of bags and boxes of fertilizer. You may find yourself wondering what your plants really want. If only you could ask them to write you a shopping list! While not too hard to master, fertilizing is a process that is easier if you just know what a few things mean. Here is our super-easy fertilizing guide that we hope helps shed some light on the subject.
Is fertilizing your plants really necessary? It depends. Many homeowners and residential gardeners feel that fertilizing regularly is their key to all landscape success, but the truth is that many people overdo it without realizing. While roses and other ‘heavy feeder’ plants enjoy regular fertilizing, most plants are simply uninterested in a constant uptake of nutrients. Some can even be adversely affected! Yikes! So the first step is to research your plants and what they do or do not want.
That being said, it is very beneficial to add either fertilizer or soil amendment to plants in certain cases. One major site for regular fertilizing is in potted plants. Especially in perennial pots, where you keep the same soil from year to year, your plants will make use of the limited supply of nutrition much faster than they would in the ground. Potted citrus and roses especially will benefit from frequent feeding.
Another major site for fertilizing is the lawn. While your grass will flourish from added nutrition, lawn fertilizer has become the major culprit in water pollution due to its overuse. An important part of sustainable gardening is keeping nutrients where you put them – not in the stormwater runoff headed to the Bay. A little goes a long way!
Do your established trees and landscape shrubs need fertilizer? What about native plants, or low-water xeric gardens? Believe it or not, the answer is usually ‘no.’ Most established plants form a unique relationship with the soil around them, and would benefit much more from a layer of bark mulch than fertilizer. As for your favorite Yucca or Protea, forget about it! While there are other things you can do to keep these plants happy, they will usually be at their best in poor soil without added nutrients, just as they are in the wild.
If you’re still standing in the aisle looking at those fertilizers, you may notice some numbers and even letters being thrown around. Something like: ‘10 – 10 – 10,’ or ‘N: 10 P: 20 K: 10.’ The key ingredients in most fertilizers are Nitrogen (N) Phosphorus (P) and Potassium (K – in the form of Soluble Potash.) If there are no letters, the three numbers will still always be in this order. Thanks to Botanical Interests Garden Co, we have this great diagram of what each of these does for your plant:
The distinction between Organic and Synthetic fertilizers is their source – either from naturally derived nutrients or from lab-produced ones. So… what’s the difference? From a plant’s view, it’s the same nutrients, only in different concentrations. Organic fertilizers tend to be lower in nutrient values (their numbers read more like 5-5-5.) Synthetic fertilizers are usually higher in nutrient value.
Synthetic fertilizing can really accelerate a plant’s rate of growth, which means shortening its lifespan. This can be a good or bad thing, depending. If you’re growing pots overflowing with annuals, maybe synthetic is the way to go, since these plants won’t live past a year anyway. If you’re going for a long life on your hedge Lavender, it may be wiser to go with something Organic.
If long life is the goal, a holistic method of feeding plants for long-term health is by applying organic compost teas to the soil or amending soil with compost in spring and fall. The compost works with the soil biota (microorganisms as well as worms) to create a healthy system. Spreading aged compost in a very thin layer over your lawn is a great fertilizer alternative, and also more eco-friendly.
One thing many gardeners don’t know is that there are good and bad times to fertilize. A lot of this is based on your plant. Azaleas, for instance, are best fertilized when they have finished blooming or when they are going into dormancy. Fertilizing before they flower can result in bunches of beautiful leaves and little or no flowers to speak of. Fertilizing citrus when there is danger of frost is also unwise – It can cause the trees to produce new growth when those succulent young leaves can get nipped in the cold. Always read the label or do a little research when you get a new plant, and you’ll be surprised to find that keeping with natural rhythms becomes second nature!
There are infinite ways of approaching gardening (and this barely nicks the surface!) but we thank you all for reading our two cents on garden subjects! We’ve been busy bees now that Spring is in full swing. If you’re looking into the future at a landscape transformation, contact our studio today!