The genus includes over 300 species;Delphinium elatumis most easily recognized.
This species towers from 5 to 6 feet tall and 2 feet wide.
The flowers are most commonly blue but also come in shades of pink, purple, and white.
The Spruce / Evgeniya Vlasova
Some types feature a contrasting eye and others produce semi-double or double blooms.
They have a sporadic growth rate, seven to 21 days from sowing.
Bloom time starts from late spring to early summer and can continue all season.
The Spruce / Evgeniya Vlasova
They are toxic to people, pets, and horses.
Spots with well-draining and loamy soil are best.
Delphiniums do best when they are transplanted, meaning they start growing indoors.
The Spruce / Evgeniya Vlasova
Get your seeds started roughly 10 weeks ahead of the last frost of spring.
The seeds will germinate sometime between 21 and 28 days.
Water frequently until baby plants spring up.
The Spruce / Evgeniya Vlasova
Delphinium Care
The Delphinium group of plants offers plenty of versatility for the home gardener.
However, this is not a plant that does well in dry heat.
A location that offers a morning sun with light afternoon shade during hot weather can improve and extend flowering.
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Soil
Well-draining loamy soil with a slightly acidicsoil pHof 6.5 to 7.0 yields the best results.
Adding compost at planting time boosts growth for these heavy feeders.
Water
Water regularly especially during hot weather.
Keep soil moist but not waterlogged because these plants are vulnerable to crown rot.
The planting bed should never dry out completely.
Water at ground level, do not wet the foliage, to discourage fungal and leaf spot problems.
A two to three inchmulch layerpreserves moisture in the soil.
These plants dislike high humidity and heat, and humidity can encouragepowdery mildewto develop.
Most perennial types are fully cold hardy to -30 degrees Fahrenheit.
Fertilizer
Delphiniums need plenty of nutrients to produce their showy flower spikes.
Work well-aged compost or abalanced fertilizersuch as a 10-10-10 into the soil at planting time.
A second system mid-season might prolong bloom and support a second bloom period.
When leaves start to turn yellow, it’s often a sign a nutrient boost is needed.
Types of Delphinium
Many popular and widely available delphiniums are cultivars ofD.
elatumorD, grandiflorawith crosses between the two identified asD.
x belladonna.Some are series of plants that share identical features but bloom in varied or combinations of colors.
Pruning
Removing mature flower spikes encourages flowering on developing side shoots.
Cutting back is repeated either in autumn or early spring to encourage new seasonal growth.
During the bloom season, deadhead delphiniums regularly to promote healthy growth.
Remove each flower individually as it fades,snipping upto the closest set of leaves or nexus of stems.
Propagating Delphinium
Delphiniums grow and multiply rapidly and are propagated by division and basal cuttings.
These methods are most successful in spring when new growth first appears.
The plants also self-seed around one year of being in the garden.
Transplant as soon as possible and keep them in a shaded spot.
Avoid materials like clay or terracotta that dry out quickly.
Pots need frequent, regular watering and a balanced fertilizer every two to three weeks.
To pot, fill the container with a loose mix of potting soil and compost or fertilizer.
Fill with potting soil or compost.
Water thoroughly at the soil level, but do not wet the foliage.
Place the pot where it will receive plenty of morning sun and filtered afternoon shade.
Overwintering
Perennial delphiniums are frost-hardy but can be damaged by cold wet soil.
Delphiniums are vulnerable to leaf spot, blight, stunting, root-knot nematodes, and viruses.
And also topowdery mildewis triggered by high humidity and a soil-borne fungus.
Healthy plants are the best defense.
Remove diseased plants immediately (especially in the case of crown rot).
Avoid soggy soil and overhead watering, keep the planting bed weed-freem and plant disease-resistant varieties.
How to Get Delphinium to Bloom
Failure to bloom can result from inadequate growing conditions.
What Do Delphinium Flowers Look and Smell Like?
They smell light and sweet and are fairly subtle in comparison to other flowers' scents.
Overcrowding inhibits air circulation which can lead to powdery mildew and the spread of other fungal and bacterial problems.
Divide or thin new growth in early spring to alleviate this problem.
Yellow leaves
Delphinium foliage should be uniform blue-green in color.
Yellowing foliage is brought on by overwatering and also could be a sign the plant lacks nutrition.
Grow delphiniums in a location or in pots with good drainage and feed them regularly.
Drooping Plants
This is a problem especially with tall varieties.
Hollow stems with heavy flower spikes need support.
Install stakes or grow delphiniums against a trellis or fence.
Flimsy plants can also result from not enough sunlight.
Plant them far enough apart to ensure each plant gets good air circulation.
Mostlarkspurare annuals while most delphiniums are perennial.
The two plants can usually be identified by differences in foliage and flower size which is larger in delphiniums.
Larkspur, ASPCA
Delphinium Plant Health Problems,Connecticut State University
