Growing Delphinium: A Complete Profile
By Growing Home Greens Team · July 29, 2026
Delphinium produces some of the tallest, most dramatic flower spikes of any garden annual or perennial, in blues and purples that are hard to find elsewhere in a flower bed. It also comes with a serious caveat: every part of the plant is toxic if ingested.
Starting it (from a nursery pot, not a seed packet)
Delphinium is almost always grown from a nursery start rather than seed. Its seed needs cold stratification and germinates slowly, often not blooming until its second year even when it does sprout. Set transplants out about 3 weeks after your last frost, and expect around 150 days to bloom. It struggles in hot summers above zone 7 under a normal spring planting. Zone 10 gardeners get around this by planting in fall instead, for bloom over the cooler winter months.
Keeping the spikes upright
Toppled stalks are the most common frustration with delphinium, and staking at planting time, not after the plant has already grown tall, prevents most of it. If staking every year sounds like too much upkeep, a compact type like Magic Fountains still needs support but carries less top-heavy risk than a full-height Pacific Giant.
Because every part of the plant is toxic if ingested, keep it out of reach of pets and children who might chew on it. This is worth deciding on before you place it, not after.
Back of the bed, away from kids and pets
Delphinium isn’t linked to specific companions or antagonists in our data. See the full companion guide for delphinium for how it’s tracked. Given its height and toxicity, place it toward the back of a bed or against a support in the Garden Designer, away from where kids or pets typically reach.
Sources: Magic Fountains Mix Delphinium Seed, Johnny’s Selected Seeds.
Companion planting guide for Delphinium · Find your planting dates
Typically viable in USDA zones 3-10. Not sure your zone? Look it up by ZIP code.
Method: Buy as a start: Buy as a nursery start and transplant outside. Delphinium is slow or unreliable from seed, so most gardeners skip seed-starting it entirely.
See exact start-indoors, direct-sow, and harvest dates for your zone →
How many Delphinium plants fit per square foot?
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 3-6 ft.
Varieties worth considering
- Magic Fountains (Delphinium elatum, Dwarf Pacific type): Johnny's Selected Seeds lists it at 36-48 inches against the 5-6 feet a full-size Pacific Giant reaches, with the same wide color range. It still needs support, delphinium spikes are heavy no matter the height, but a shorter plant is a shorter lever arm, and it's noticeably less prone to snapping over in wind than the tall types. (source)
- Pacific Giant 'Galahad': Chicago Botanic Garden lists this white-flowered Pacific Giant at up to 6 feet, taller than Magic Fountains' dwarf 3-4 feet. Grow it if you want the full dramatic height and have a wall or sturdy stake ready, not a compromise on staking effort. (source)
- Pacific Giant 'Black Knight': Also a full-height Pacific Giant per Chicago Botanic Garden, deep indigo-blue rather than Galahad's white. Same staking commitment as Galahad, just a different color at the top of the spike. (source)
Cited from the source shown next to each variety. We haven't grown these ourselves yet, so treat this as a research-backed starting point, not a personal endorsement.
Where to buy delphinium starts
Delphinium is almost always bought as a nursery start rather than seeded. Check a local nursery or garden center; we haven't vetted online start/plant suppliers yet.
See it growing
Search YouTube for "growing delphinium" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
%20placement%20well%20away%20from%20pets%20and%20kids.)
Pin this for later
Growing Delphinium: A tall, dramatic spike flower that needs staking, patience, and (in most households) placement well away from pets and kids.
Save to Pinterest