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.
Dahlia HS Flame
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.
Asiatic lily Patricia’s Pride
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.
I understood all annuals are not the same when it comes to fertilizers. Particularly dahlias. What should be used with them?
Hi Cindy –
In general, flowering plants should be given a low-nitrogen fertilizer such as 5-5-5 (nitrogen-phosphorus-potassium). If they get too much nitrogen, they will produce more foliage than flowers. I fertilize my flowering annuals (in containers and in beds) every two weeks. It seems like they just can’t get enough.
As for dahlias, there are many different opinions about how often to fertilize. I’m sure much of it is location based, due to variations in temperature, soil and moisture levels. My current strategy is to fertilize every couple weeks during the first half of the season. My goal is to help the plants bulk up quickly to outrun the slugs and get to flowering stage as fast as possible. Then for the rest of the season I back off and fertilize just once a month with a 5-5-5 liquid fertilizer. Also, I have found dahlias love compost, so I dig that into the soil when planting and also top-dress around the plants in early July, before they get too big.
Fertilizing, like all things gardening, requires some experimentation to discover what works best in your location. Weather conditions also have a big impact on performance, so even the same fertilizing strategy won’t always give you the same results. Just part of the fun!
I planted Shasta daisies about 6 weeks ago. After the blooms that were on them died they haven’t bloomed again. They were planted in a sunny location and I gave them about a tbsp of an organic fertilizer. The same thing happened last year and I pulled those up. I have planted other perennials and they are thriving and blooming. I would appreciate any help. This is an excellent article and in general very helpful. Thank you.
Hi Becky – Did you cut off the spent flowers? This encourages plants to rebloom. Not all perennials bloom more than once during the growing season. Some of this depends on the variety and some on weather/climate. Most perennials flower during their specific bloom time and then rest for the remainder of the year. Peonies, poppies and lilies behave like this. Some early summer perennials will re-bloom after a few weeks or start up again in the fall. I grow a Shasta daisy named ‘Becky’ that I have found is a good re-bloomer as long as I cut off the flowers as soon as they go by — and fertilize after the first big flush of blooms. Hope this is helpful!
How much liquid bloom fertilizer should I put in a gallon of water.
Hi – I am not familiar with the product. Check the label or contact the manufacturer.
Great article, bookmarked for future use, thanks! I bought a potted plant (leaf looks like a mum, but yellow flower looks like a daisy?)) that I cut back after first blooms were spent earlier this summer. Replanted in a 10″ pot using potting soil with vermiculite and peat, and a layer of gravel for drainage, set out on the deck and pretty much forgot about it for the rest of the summer, except for watering and a little liquid 10-15-10 fertilizer every few weeks. To my surprise, now in September, it’s 2 feet tall and covered with a massive amount of buds. But the bottom leaves are yellowing. I’m hoping it will get to bloom before a killing frost (I’ve since been sheltering it at night, I live in zone 6) but worry about the loss of leaves. Any suggestions? I hope to overwinter it as well. Thank you again for such a helpful article!
Hi Jennifer – There are mums with single, daisy-like flowers, so I’m going to assume that’s what you have. Mums and asters often lose their lower leaves before or during the time they are flowering. Does’t look good, but there’s no need to worry (and nothing you can do!). Sounds like you are doing the right thing. Hopefully the weather will hold and you’ll get to see the flowers. Do you plant to overwinter it in the ground? If so, and assuming it survives, next year the plant will sort itself out and probably bloom a little earlier. If this is a tall variety, you can pinch it back in early summer before the buds form. This helps keep mums from flopping. Though they flower a week or two later, but it’s worth it.
what fertilizer is best for angel wing begonia. want blooms plant is 5 ft. tall and very healthy.
Hi Candice. That’s a very large begonia! It may not need much fertilizer if it is growing well and staying healthy. It would be safe to use any all-purpose liquid plant food that’s recommended for indoor plants. Just don’t overdo it.
I have a huge shasta daisey which I planted several years ago. I usually don’t cut it back but wonder if I should???
Are there different varieties of shasta daisey?? Mine bloom in late September/October in zone 7a/Virginia
Hi Donna – there are quite a few different Shasta daisy cultivars, but are you sure what you have is a Shasta daisy? From the bloom time, it sounds like it may be an aster. Asters are often purple or pink, but they also come in white. It’s almost always good practice to cut perennials back in fall or early spring. This keeps the garden looking neat and gives the plant a fresh start in the spring.