- Delphinium flowers beautify the summer garden with showy, spiky blooms on a tall, sometimes towering stem. Delphiniums come in a range of shades. Many gardeners wonder how to grow delphinium and some avoid planting them after hearing that the plant is difficult to grow. What are the secrets to the correct care of delphinium? Read more for tips about delphinium planting and how to get the best performance from growing delphinium plants. - One commonly thinks of delphinium plants (Delphinium) as having true blue flowers, which is the most common color. But numerous hybrids are available in shades of pink, lavender, red, white and yellow. Blooms may be single or double. - Delphinium planting is normally at the back of the bed, where flower spikes can reach 2 to 6 feet tall. Delphinium flowers are often planted in masses or groups. Shorter varieties are useful in other areas of the garden. - Planting Seeds - 1. Fill a seed tray to within 1/2 inch of the top with sterile seed-starting compost. Mist the compost with water until the top 1 inch feels wet and let it soak in for five minutes before sowing the delphinium seeds. - 2. Place the delphinium seeds on the surface of the compost, spacing them one inch apart. Cover them with a 1/4-inch-thick layer of seed-starting compost. Mist it with water and gently firm the surface. - 3. Place the seed tray outdoors in a sheltered, lightly shaded garden area where temperatures stay between 65 and 75 degrees Fahrenheit during the day. Provide warmth with a propagation mat if the weather is unusually cool. - 4. Maintain a light level of constant moisture in the top 1 inch of compost while the delphinium seeds germinate. Let the surface dry slightly between waterings to keep the seeds from rotting. - 5. Watch for germination in 10 to 20 days. Water carefully after germination to prevent fungal infections. Drizzle the water directly onto the compost rather than watering from above. - 6. Grow the delphinium seedlings in their nursery tray until they reach at least 1 inch tall and have two pairs of true leaves. Scoop out the seedlings and transplant them into individual 3-inch pots filled with potting soil. - 7. Keep the delphinium seedlings well-watered for the rest of the summer. Feed them with 12-12-12 fertilizer diluted to one-fourth strength six weeks before transplanting them. - 8. Place the pots at the intended planting site every day. Extend the time by one hour every day for one week. This acclimates the delphiniums to normal outdoors conditions before you transplant them. - 9. Plant the delphiniums in a partly shady bed with deep, moist and fast-draining soil. Space the plants approximately one foot apart. Mulch heavily and water regularly during dry weather." - Grow delphinium plants in a sunny area with soil that is consistently moist. Don’t let them dry out. Mulch helps retain moisture and keeps roots cool. Performance of this specimen is enhanced when growing delphinium plants in neutral to slightly alkaline soil pH. Soil should be well-draining. - Care of delphinium should include regular fertilization in spring when the plant begins to grow, and during the flowering period. Work in well-composted organic material such as rotted cow manure, or use a basic 10-10-10 granular fertilizer. Yellowing foliage or stunted growth often indicates the plant needs more fertilizer. - Sun exposure is another aspect of care of delphinium that the gardener must get right for the showy blooms to appear. Gentle morning sun is preferable to the delphinium plants, which are picky about extreme differences in temperatures. Provide afternoon shade, especially when planted in hotter zones.