If you want your dahlias to grow strong and keep those gorgeous blooms popping all season long, regular feeding is the secret sauce. Here’s the lowdown on how and what to feed your dahlias for the best results.
The Best Fertilizers for Dahlias
Dahlias really thrive when you stick to organic options. My top picks for keeping them happy are:
- Cow manure
- Pigeon manure
- Well-aged compost
- Horn meal or horn shavings
If you don’t have access to the “farm-fresh” stuff, you can also use pre-fertilized potting soil or a standard slow-release universal fertilizer from your local garden center.
A Quick Warning About Horse Manure
While horse manure is a popular garden amendment, be careful! It needs to be well-aged and properly composted. Fresh horse manure contains a lot of ammonia, which can actually “cook” or overheat your dahlia tubers, causing permanent damage.
Skip the Synthetic High-Nitrogen Fertilizers
It’s tempting to grab a standard synthetic fertilizer, but be careful with anything too high in nitrogen. While nitrogen is great for leafy growth, too much of it will leave you with a giant green bush and zero flowers. The plant puts all its energy into the stems and leaves rather than those beautiful blooms we’re after.
Feed Them Right at Planting Time
The best time to start your nutrient program is the very day you put them in the ground. I always recommend mixing some fertilizer directly into the soil when planting or transplanting. This gives the tubers a “power breakfast” that supports them right from the start.
Feeding Potted Dahlias
If you’re growing dahlias in pots, start with a high-quality, nutrient-rich potting soil. A good pre-fertilized mix acts like a slow-release fertilizer, keeping your plants fed for quite a while. If they need a little boost later in the season, a liquid universal fertilizer or a bulb-specific fertilizer works great. Just make sure you don’t exceed the dosage on the label—more isn’t always better!
When to Stop Fertilizing
If you used a slow-release fertilizer at planting, you’re usually set for the season. You can add a little universal fertilizer here and there if the plants look like they need a pick-me-up, but stop everything by August. Dahlias can easily be over-fertilized; if they have too many nutrients in their system late in the year, the tubers won’t “harden off” properly for winter storage and might rot or die before spring.
Pro Tip
Many expert gardeners swear by adding a small handful of horn shavings to every single planting hole. It’s a fantastic way to ensure your dahlias have a steady supply of nutrients from day one, leading to impressive growth and stunning flowers!
