If you want to grow a beautiful delphinium flower, let me suggest you stick to a few basic techniques.
The first is to give this plant full sunshine. Reduce the sunshine and you ‘ll reduce either the size or the quality of the bloom.
The second is to understand this plant is a greedy feeder. It is one of the few perennials that thrives on a little extra food without getting long, leggy and falling over. The easiest way to do this is to toss an extra shovel of compost around each plant in the spring.
Or, give the plant a monthly watering with liquid fish emulsion. Either of these gardening tips will work. What is clear is that if you don ‘t feed this plant, it will not grow as big or have as many flowers as it could. Overfeeding with nitrogen will shorten the lifespan of the flowers so don ‘t overdo it with chemical fertilizer and think you ‘re doing a good thing.
Third, it does help to stake each delphinium flower. These flower stalks are going to be in the 5-6 foot tall range and a little support goes a long way. I use old Christmas tree branches stuck at the base of the plant. This gives the first few feet of growth adequate support but doesn’t stand out like a sore thumb in the garden.
Mind you, it also helps not to plant them in a direct windy garden location in the first place.
Starting your own seed is not overly difficult. The seed does require a pre-chilling to get a good germination rate. Some gardeners suggest you put the seed in the freezer for a week or two to chill it.
Putting dry seed in a freezer is often a very good way to kill it.
Instead, put the seed in a baggie with a handful of just-damp vermiculite. Put this baggie in the crisper of the fridge for 90 days, then sow the seed.
Space the delphinium flower seed 3/4-inch apart in the flower pot when sowing. Barely cover the seed – the objective is to keep the damp soil around the seed, not eliminate all light. Keep the soil damp – not swampy. Always water with warmish water. You ‘ll see germination in 14-21 days.
Transplant into individual pots when the seedling has 4 true leaves (not the first seed leaves). Grow cool at 55-60 F in full sunlight to avoid stretched ugly plants.
The delphinium flower will not emerge until the second year from seed.
A delphinium can also be divided if strong and healthy and believe it or not, tip cuttings of delphiniums can also be rooted if you know what you ‘re doing. Rooting tip cuttings is not for the faint of heart or beginners without equipment.
Delphiniums make excellent cut flowers (if you can stand to cut such a lovely spike) and will last upwards of 14 days from a freshly cut stem.
You can expect a delphinium flower plant to last 3-5 years in the garden without renewal and then they ‘ll likely weaken and die off. Be prepared to collect your own seed and sow it as replacements.
Can You Grow a Delphinium in a Pot?
Any plant can be grown in a pot if you give it a big enough pot. In this case, a delphinium is a rather tall plant so you really do want to use a big pot (16″ will do) so it doesn’t tip over the pot. Small and light pots will flop all over the place in any kind of wind once the plant starts to bloom and you’ll regret it when you break off the stem.