Canada Day long weekend is at our doorstep and each year we like to highlight a Canadian Classic plant. So, for this year, let’s talk about Delphiniums and describe who they are, what their place is in the garden cycle, and how to best care for them.
Lovers of cool weather, Delphiniums have graced Canadian gardens for decades adding height to gardens with their tall stately spires. Delphiniums are native to the northern hemisphere, growing in mountainous regions of places like northern Africa and the Alps. Delphiniums hail from the Buttercup family (Ranunculaceae) and there are now over 400 varieties available. Delphiniums range in colour offerings from white to pinks and lavenders to shades of blue. One of the draws to this summer blooming flower is their true blue colour. Not many flowers are truly blue. Delphiniums also make great cut flowers. Delphiniums are a shorter lived perennial, spanning 3 – 4 years.
Delphiniums are divided into 3 basic classes:
- Delphinium cultorum (also known as Delphinium elatum) – the tall group
- grow 3 – 6 feet tall
- have complex or double flowers
- series such as: Magic Fountain & New Millenium
- Delphinium belladonna group – the midrange group
- grow 3 – 4.5 feet tall
- series such as: Conneticut Yankees
- Delphinium grandiflorum (also known as Delphinium chinensis) – the short group
- grow 1.5 – 3 feet tall
- varieties such as: Blue Butterfly, Blue Pygmy
Delphiniums grow best:
- in full sun areas with a minimum of 6 hours of sunshine. Because of their susceptibility to powdery mildew, be sure to keep good air circulation around the stalks by thinning back leaves when the foliage becomes very dense
- with fertilizer – Delphiniums are heavy feeders, so a slow release fertilizer (10-10-10) plus compost and mulch would work well. Another option to meeting their feeding needs is to fertilize every week or two with a soluble 20-20-20 or 15-30-15 or Nature’s Source fertilizer.
- when staked – the tall varieties can be staked with a tomato cage while they are just beginning to grow and weave them through as they continue to lengthen.
- when deadheaded – cut off the spent flower spires where they meet the main stalk and it will sprout new shoots lower down, which will lengthen their period of bloom.
One last thing to bear in mind about Delphiniums is that all parts are poisonous, so plant them in a place where young children won’t get at them. Eating any of the plant parts can cause nausea, vomiting, abdominal pain or muscular spasms.