Learning how to fertilize dahlias is easy, and one can break it down into three easy steps. They include knowing the best fertiliser, when to fertilise, and how to fertilise dahlias correctly in the United Kingdom. You don’t have to feel overwhelmed with the information about fertilising these flowers because they are generally easy to grow anyway.
However, like all plants, knowing the fertiliser needs and practices for dahlias is crucial to their growth and survival. You can also consider cultivating them or starting them in the greenhouse to maintain their ideal growing conditions. This way, you don’t have to worry about fluctuating weather and temperatures that can affect their growth and health.
How To Fertilize Dahlias Correctly
More often than not, the most crucial factor to remember when fertilising dahlias is the soil itself. It’s also worth noting that the plants do not require fertiliser when you have just started them because they have no feeder roots to use the fertiliser yet. And if you’re establishing dahlias, whether outdoors or in the greenhouse, moist soil and mulching are enough, and adding water is unnecessary since overwatering can cause rot.
Know the best fertiliser
According to the American Dahlia Society, the best way to determine your dahlias’ appropriate fertiliser is by checking your soil. Checking the soil is perhaps one reason why the growth in the polytunnel puts you at an advantage since you can modify the dahlias environment. After you checked the soil’s pH and composition, you can then decide on the fertiliser to use.
Dahlias can use high nitrogen fertiliser throughout the season but remember to minimise the nitrogen at the end of the season. Nitrogen will encourage bush growth and large flowers, but you have to control its amount since too much can lead to poor growth and low-quality tubers. Instead, potassium is more vital in helping create vibrant dahlias while also developing their roots faster.
Oregon State University also recommends 5 pounds of a 0-20-20 fertiliser per 100 square feet for dahlias. Emphasis is necessary for monitoring the nitrogen and focusing on potassium and phosphorus. If you’re new to planting, you’ll find formulas where the first number is lower than the last.
When to fertilise
The University of Vermont Extension mentioned adding manure or compost in the soil before planting. Then you can add a quarter pound of a balanced fertiliser per 10 square feet after a month. You’ll benefit from fertilising dahlias 30 days after planting because it encourages the tubers to produce sprouts and stems.
You can also fertilise after the plants’ sprout, then every four weeks from the middle of the summer until the beginning of autumn. This way, dahlias can enhance their root system and have enough energy to enhance flower production. Dahlias are heavy feeders, and following these schedules should give them their requirements to grow well.
How to fertilise
First, you want to know how much fertiliser you’ll give to your dahlias. Fertilisers often show their recommended amounts per square foot, so check it first to avoid over-or under-feeding. But in general, you can have half a cup of fertiliser around your plants to create a 2-foot ring that you’ll work into the soil.
Creating a ring is best when you’re just starting, and then water it up to help with absorption and prevent burning the roots. While dahlias are heavy feeders, it can be confusing as some UK gardeners swear that they don’t even need fertilising. Therefore, checking your soil beforehand should give you the gist of your plant’s needs for feeding.
Another tip that you have probably read for fertilising dahlias is treating it similarly to a tomato plant. Treating similarly to a tomato plant means dahlias will work well with an all-purpose fertiliser when you plant them and then switching to a low nitrogen liquid fertiliser once a month when they start blooming. If this is the practice you chose, remember to stop fertilising early in September if you want to use tubers later.
Additionally, you can promote better aerial growth if you fertilise with a high-phosphorus feed in the early summer every three weeks. You can then stop feeding when dahlias die back in late summer as the plants will soon be undergoing dormancy in winter. You want to discourage dahlias from producing foliage by the end of the season so that they have enough nutrition in their tubers.
You can ensure flowering plants like dahlias grow and bloom healthily regardless of your location by using a greenhouse. However, a significant part of their success is on you, including knowing how to fertilize dahlias properly. Start by identifying the best fertiliser, when it is the right time to fertilise, and how to fertilise dahlias.
One gardener in the UK might say dahlias are heavy feeders, while another can swear that they are low maintenance when it comes to feeding. With the many tips for fertilising dahlias from various gardeners in the UK, the concepts can be contradicting. To avoid getting overwhelmed, remember that your soil is the first factor to consider and that until there are no feeder roots that have developed yet, fertilising has no use.
Therefore, check your soil quality to adjust the feeding accordingly. You can also treat dahlias the same way you’ll fertilise tomato plants and start from there.