How and Why to Use Flower Fertilizer
When you think about it, a plant’s ability to make flowers out of nothing more than soil, water and sunshine is a pretty amazing feat. As flower gardeners, all we need to do is create the best possible growing conditions for our plants to work their magic.
The plants in our gardens need access to a whole menu of different soil nutrients, in varying amounts and at different times during the growing season. Even the best garden soil rarely provides all the nutrients that a flowering plant needs for peak performance. So it’s up to gardeners to close the gap.
How to Choose a Flower Fertilizer
An all purpose flower fertilizer contains all three major plant nutrients: nitrogen (N), phosphorus (P) and potassium (K). Some fertilizers may also contain small amounts of minor nutrients such as magnesium, calcium, sulfur, iron and boron.
The N-P-K ratio on the package (such as 5-10-10 or 5-5-5) tells you the percentage – by weight – of each major nutrient. Broadly speaking, a 5-10-10 ratio is about right for most flowering plants. Here are a few other things to know when choosing a flower fertilizer:
• Granular organic fertilizers are a long-term investment in better soil. It takes time and a web of soil microbes to gradually convert these organic compounds into readily available plant nutrients. You can expect organic fertilizers to release their nutrients slowly, over the course of one or more growing seasons.
• In comparison, granular synthetic fertilizers are water soluble and begin releasing their nutrients within a matter of weeks. This is a big benefit when plants are hungry. But synthetic fertilizers do not increase the long-term fertility of the soil and they also do not feed beneficial soil organisms. It’s also important to always follow application rates on the package, as too much fertilizer can damage your plants.
More Fertilizer Options
• Time-release synthetic fertilizers (such as Osmocote) are formulated to provide a steady supply of nutrients for 30-60 days. This is a convenient solution, especially for container plants. How long the nutrients are actually available, depends on how much rain you get and/or how often you water.
• Plants can absorb liquid fertilizers (such as fish emulsion, compost tea and Miracle Gro) almost immediately. These are usually applied as a soil drench, although most can also be sprayed directly on the foliage. Foliar feeding is especially effective during critical growth stages such at transplanting time or when plants are forming buds. It is also very helpful for reviving plants that are under stress from weather, pests or disease.
If you are unfamiliar with the role of N-P-K in plant health, the differences between organic and synthetic fertilizers, and how soil pH impacts nutrient availability, visit our website to read the full article.
When and How to Use a Flower Fertilizer
Not all plants require the same amount of nutrients or need them at the same time during the growing season. Generally, early summer is the best time to fertilize annuals and perennials, because this is when they are growing most vigorously. Here are some additional recommendations for timing:
• Seedlings and other young plants should be fertilized sparingly to avoid damaging their tender roots. Mix liquid fertilizers to half strength or even less.
• Flowering annuals need to be fertilized all season long, right through early fall. Application rates vary by product, so follow the instructions on the label.
• Early spring is the best time to fertilize flowering perennials, shrubs and trees. Fertilize again in midsummer when the plants are growing vigorously. Do not fertilize in late summer or fall.
When applying flower fertilizer, here are some general rules:
• Mix granular fertilizers into the soil at planting time. For established plants, broadcast the fertilizer on the soil surface in spring and gently mix it into the top inch or two of soil.
• Sprinkle time-release fertilizers on the soil surface.
• Dilute water-soluble fertilizers at the recommended rate and apply them to the soil surface. For best results, water well both before and after fertilizing.
More Fertilizer Isn’t Necessarily Better
Though you don’t want your plants to go hungry, you also need to avoid overfeeding. Too much nitrogen will encourage plants to produce foliage rather than flowers. An excess of phosphorus can make it difficult for plants to absorb essential micronutrients such as iron and zinc. Too much potassium makes it more difficult for them to absorb calcium.
There’s another problem with applying too much fertilizer, especially water-soluble ones. Excess nutrients leach out of the soil and find their way into in streams, ponds and groundwater where they can damage ecosystems and pollute drinking water. For best results, always follow the package instructions for proper application rates and timing.
Fertilizing Flowers in Containers vs. in Gardens
Most home gardeners grow flowers in containers as well as in their gardens. Container-grown plants call for a slightly different approach to fertilizing.
The best growing medium for pots and planters is a soilless mix that contains peat moss, perlite and vermiculite. These mixes encourage good root growth and resist compaction, but they contain few if any nutrients. At planting time, it’s good to fortify the soil with compost and granular fertilizer. But within a couple of months, daily watering will have washed most of these nutrients out of the soil.
Have you ever wondered why the planters at high end restaurants and public gardens always look so great? It’s because they are on a regular fertilizer program and are probably being fed every week from May through September.
You can achieve the same success by watering your container plants once per week with a water-soluble fertilizer mixed to half strength. Alternatively, apply timed-release granules to the soil surface and reapply every 6 weeks or so (depending on rainfall and how often you are watering).
Make this year’s flower garden more beautiful than ever by giving your plants the nutrients they need to produce an abundance of colorful blooms.