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, our task is to create the best possible environment for our plants to work their magic.
Plants need access to many 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. It’s up to gardeners to close the gap.
Dahlia HS Flame
How to Choose a Flower Fertilizer
Most flower fertilizers contain all three major plant nutrients: nitrogen (N), phosphorus (P) and potassium (K). Some also contain small amounts of the minor nutrients magnesium, calcium, sulfur, iron and boron. The N-P-K ratio on the package (such as 5-10-10) tells you the percentage – by weight – of each major nutrient. Broadly speaking, a 5-10-10 ratio is about right for flowering plants. Here are a few other things to know about flower fertilizer:
- Most granular organic fertilizers release their nutrients slowly over the course of one or more growing seasons. In comparison, granular synthetic fertilizers are more water soluble and begin releasing their nutrients within a matter of weeks. Most of these fast-release nutrients will either be absorbed by the plants or washed out of the soil by rain or watering.
- Time-release fertilizers (such as Osmocote) are formulated to provide a steady supply of nutrients for 30-60 days. How long these nutrients are available depends on how much rain you get, how often you water, and how hungry your plants are.
- Liquid and powdered fertilizers (such as fish emulsion, compost tea or Miracle Gro) are water soluble and plants can absorb them almost immediately. They are usually applied as a soil drench or can be sprayed directly on the foliage. Foliar feeding is effective during critical growth stages such as transplanting time and bud formation. It can also be used to help plants overcome 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, the best time to fertilize plants is early summer when they are growing most vigorously. Here are some additional recommendations for timing:
- Seedlings, transplants and other young plants should be fed lightly until they have established a good root system. Dilute liquid fertilizers to half strength.
- Annuals should be fertilized consistently all season, right through early fall. Application rates vary by product, so follow instructions on the label.
- Perennials, shrubs and trees, may be fertilized in the spring as soon as the soil warms up. Fertilize again in midsummer when the plants are growing vigorously. Do not fertilize in late summer or fall.
Asiatic lily Patricia’s Pride
When you’re 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 and lightly mix it into the top inch or two.
- 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 both before and after fertilizing.
More Isn’t Always Better
Though you don’t want your plants to go hungry, overfeeding can cause problems. An overabundance of nitrogen encourages plants to produce foliage at the expense of flowers and fruit. Too much phosphorus can make it difficult for plants to absorb essential micronutrients including iron and zinc; too much potassium makes it difficult for them to absorb calcium.
There’s another problem with applying more fertilizer than your plants need. The excess nutrients may leach into in streams, ponds and groundwater, where they can damage ecosystems and pollute drinking water. For best results, follow package instructions for proper application rates and timing.
Fertilizing Flowers in Containers vs. Gardens
Most home gardeners grow flowers in containers as well as in a garden. These two different growing environments call for two different approaches to fertilizer.
The best growing medium for pots and planters is a soilless mix that contains peat moss, perlite and vermiculite with little or no nutrients. At planting time, it’s good to fortify the soil with compost and granular fertilizer. But in most cases, your plants will absorb those nutrients within about a month. The rest will be washed away by daily watering.
To keep container plants lush and healthy, and to ensure they have enough energy to produce flowers, you need to feed them regularly. Have you ever wondered why your planters never look as good as the ones at high end stores, restaurants and public gardens? It’s mostly about fertilizer (and partly about dead-heading). Water your container plants with a water-soluble fertilizer every 1 to 2 weeks or apply timed-release granules to the soil surface about every 6-8 weeks.
Summer is here and the growing season is in full swing. Now is the most important time to be feeding your plants. Give them a boost and enjoy the rewards!
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.