Dahlias are prized for their beautiful, colorful blooms that brighten up gardens from midsummer into fall To get the most prolific flowering from your dahlia plants, proper feeding is key. One fertilizer that works exceptionally well on dahlias is tomato feed The high potassium content helps produce stronger stems and more abundant blooms.
Why Tomato Fertilizer is Ideal for Dahlias
Tomato fertilizer is formulated to promote fruiting and flowering in tomato plants. The same properties that make it great for tomatoes also benefit dahlias. Here’s why tomato feed is an ideal choice:
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High potassium content – Potassium is the nutrient most vital for flowering Tomato feed has extra potassium to fuel fruit and flower production
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Low nitrogen – Too much nitrogen leads to excessive foliage at the expense of blooms. Tomato fertilizer has reduced nitrogen.
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Added micronutrients – Micronutrients like magnesium and calcium contribute to plant processes needed for flowering. Many tomato feeds contain these.
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Acidity – Tomatoes and dahlias prefer slightly acidic soil. Tomato fertilizers help maintain ideal pH levels for these plants.
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Liquid application – Liquid tomato feeds allow for foliar absorption and quick nutrient delivery to aid flowering.
When to Start Using Tomato Fertilizer
When should you start feeding your dahlias with tomato plant food? Follow this guideline:
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Planting until sprouting – Use a balanced starter fertilizer to give developing tubers an early boost.
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Spring growth – Early rapid growth requires more nitrogen, so use a balanced all-purpose fertilizer.
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Flower bud formation – As soon as buds begin to form, switch to tomato feed to nourish the blooms.
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Peak flowering – Continue applying tomato fertilizer every 2-3 weeks through the main flowering period.
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Fall – Taper off fertilizer as plant energy goes back into the tubers in fall.
Adjust timing appropriately for your climate and the variety of dahlia you are growing.
Application Rate and Method
Always follow label instructions when applying any fertilizer. For tomato feeds, typical application rates are:
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Dry tomato fertilizer – Apply at 1-2 tablespoons per square foot. Scratch into soil around plants.
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Liquid tomato fertilizer – Mix according to label and apply 1 quart diluted solution per square foot.
Two key tips:
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Never apply dry fertilizer directly on plant leaves, as it can burn.
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For containers, use half the recommended rate to avoid buildup in the potting mix.
You can apply liquid tomato feed via soil drenching or foliar spraying. Foliar feeding is great for a quick boost when buds or flowers are developing. Homemade compost tea also makes an excellent foliar spray.
The Best Tomato Fertilizers for Dahlias
There are many quality tomato feeds on the market. When choosing one for your dahlias, look for:
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High potassium – Should be the first number on the NPK ratio.
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Added calcium and magnesium
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Options for liquid application
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Organic or synthetic formulas
Here are some top tomato fertilizer picks for dahlias:
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Espoma Tomato-Tone – Organic granular, also contains beneficial mycorrhizae
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FoxFarm Big Bloom Liquid – Concentrated organic formula for foliar or soil feeding
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Miracle-Gro Tomato Plant Food – Popular synthetic liquid fertilizer
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Neptune’s Harvest Tomato & Veg – Liquid formula with fish & seaweed oils
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Jobe’s Organics Tomato Granular Fertilizer – Time-released organic nutrient source
Tips for Using Tomato Fertilizer on Dahlias
Follow these tips to safely and effectively use tomato fertilizer on your dahlias:
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Test your soil pH and amend if needed – Tomatoes and dahlias prefer slightly acidic soil.
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Rotate fertilizers for balanced nutrition – Don’t rely solely on tomato feed; alternate with compost tea or all-purpose fertilizer.
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Watch for burn signs – Leaf burn can occur from excessive or direct application to foliage.
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Adjust rate for container plants – Use half strength tomato feed for potted dahlias.
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Complement with compost – Compost provides nutrients and improves moisture retention.
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Stop fertilizing in fall – Allow tubers to harden off naturally as foliage starts dying back.
The Results of Feeding Dahlias Tomatoe Fertilizer
When fed with a quality tomato fertilizer, here are some of the results you can expect:
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More blooms – The high potassium fuels increased flower production.
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Larger blooms – Key nutrients result in bigger individual blossoms.
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Bright colors – Pigments are enhanced, creating more vivid flowers.
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Stronger stems – Thicker, sturdier stems keep top-heavy plants upright.
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Extended flowering – Plants continue blooming prolifically into fall.
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Plant health – Nutrients strengthen the overall plant for better resistance to diseases.
Avoid Overuse of Tomato Fertilizer
While tomato feed is beneficial for dahlias, overfertilizing can be detrimental. Use the fertilizer as directed to avoid issues like:
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Excess foliage growth – Too much nitrogen leads to more leaves rather than flowers. Stick to the lower nitrogen tomato formulations.
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Root damage – Concentrated dry fertilizer on roots or tubers can burn and damage them.
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Flopped stems – Weak, floppy growth results from unbalanced nutrition.
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Fewer blooms – Excess nitrogen triggers more leaf growth instead of flowers.
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Smaller flowers – Some nutrients in excess can limit bloom size.
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Inhibited tuber growth – Too much fertilizer inhibits nutrient storage for next year.
Pay close attention to how your dahlias respond and adjust your feeding accordingly.
The Ideal Flower-Fueling Feed
Tomato fertilizer contains the ideal blend of nutrients, in the right ratios, to coax the most blooms from dahlias. Follow best practices for using tomato plant food, and your dahlia garden will put on a spectacular floral display!
The Value of Pinching and Staking
When the plants are 12” tall, pinch off the top of the main stem. This will stimulate lateral branching and result in more stems and more flowers. For instructions, see HERE.
Border dahlias are self-supporting, but full size dahlias can grow 3 to 4 feet tall and benefit from being staked or caged. Read about staking options HERE.
Know Where and How to Plant
Dahlias bloom best when they are planted in full sun and fertile, well-drained soil. Border dahlias can be planted 15” apart from center to center; standard types are usually spaced about 18” from center to center.
Loosen the soil to a depth of 12”. Add compost and all-purpose granular fertilizer to the planting area and mix well. Dig a hole and plant the tubers, keeping the stem(s) or sprouts upright. The top of the tubers, where the sprout emerge, should be positioned no more than 1-2” below the soil surface. Backfill the hole with soil.
Fast growing Dahlia and Tomatoes
FAQ
Can I use tomato feed on dahlias?
I’ve used tomato feed in the past as it’s formulated to grow huge tomatoes and will do the same for dahlia blooms. Nowadays, I generally use fertilisers with a ratio of around 2-12-8 from late summer onwards and it works perfectly.
What is the best fertilizer for dahlias?
According to the experts, “Dahlias require a low nitrogen fertilizer, such as used for vegetables. We recommend high percentage potassium and phosphorus fertilizers such as a 5-10-10, 10-20-20, or 0-20-20. First applications should be within 30 days of planting and repeated again approx. 3-4 weeks later.
What do dahlias like to be fed?
Apply an all-purpose 5-5-5 fertilizer at planting time and when they start blooming, feed them once or twice a month with a low nitrogen liquid fertilizer.
What is the best food for dahlias?
Bat guano and blood meal are good fertilizers. Of course all types of aged manures are the classic fertilizers for organic gardeners. Chicken manure works great but needs to be applied in the Fall as it is too “hot” (too much nitrogen all at once) for dahlias.