If you've ever dreamed of growing those towering blue flower spikes in your garden, let me tell you: growing delphiniums from seed is totally doable — you just need to know the one trick most beginners miss. I've killed my fair share of delphinium seedlings over the years, and I can tell you from experience that it's almost always because I skipped the cold start. Pop those seeds in the fridge for a week before planting, and you'll see germination rates jump from nearly zero to about 80 percent. In this article, I'll walk you through the exact steps I use to get tall, healthy delphiniums from seed every time — no expensive equipment, just patience and a few clever tricks.
E.g. ：Persimmon Tree Fertilizer: How Much to Use (and When to Stop)
- 1、Growing Delphiniums from Seed
- 2、How to Plant Delphinium Seedlings
- 3、Common Delphinium Growing Mistakes and How to Avoid Them
- 4、Delphinium Care Through the Seasons
- 5、Getting the Soil and Timing Right for Seedlings
- 6、How to Plant Delphinium Seedlings Like a Pro
- 7、Common Delphinium Growing Mistakes and How to Avoid Them
- 8、Delphinium Care Through the Seasons
- 9、FAQs
Let me tell you something about delphiniums — they are the ultimate "looks good, high maintenance" plant. I've seen them tower over 8 feet in a friend's garden, absolutely covered in vivid blue and violet flowers. It's a jaw-dropping sight. But getting there from a tiny seed? That takes a bit of know-how. I've grown them a few times now, and I'll walk you through exactly how to do it without pulling your hair out.
When it comes to growing delphiniums from seed, most people get tripped up right at the start. They either skip the cold period or they plant them too late. I've made both mistakes myself, and I'm here to tell you: it's totally avoidable. The trick is to understand what the seed needs before it even touches the soil. Once you get that right, the rest of the process is just about good habits and a little patience. Stick with me, and you'll be rewarded with those incredible towering flower spikes in no time.
Growing Delphiniums from Seed
Understanding the Cold Start Process
You absolutely have to trick delphinium seeds into thinking they've been through winter. That means a cold start. Don't skip this step — I learned the hard way that it's non-negotiable. If you treat these seeds like tomato seeds, you'll be staring at empty trays for weeks.
I remember the first time I tried growing delphiniums from seed. I was so excited, I just planted them straight into some potting soil like I would with zinnias. Nothing happened. I waited two weeks, three weeks, four weeks. Not a single sprout. I was about to throw the whole tray out when a friend asked, "Did you cold-stratify them?" I had no idea what that meant. That's when I learned about the cold start. Now, I pop the seeds in the fridge for a full week before I do anything else. You don't need a special machine — just your kitchen fridge. I put the seeds in a sealed plastic bag with a damp paper towel. It's called stratification, and it mimics the natural winter cycle. For successful growing delphiniums from seed, this one step makes the difference between a tray full of seedlings and a tray full of nothing. After the week is up, I plant them immediately. They usually germinate in 10 to 14 days. The science is simple: the cold breaks the seed's dormancy. Without it, the seed thinks it's still winter and refuses to wake up.
Indoor vs. Outdoor Sowing: Pros and Cons
I'm a big fan of starting most seeds indoors. For delphiniums, it gives you way more control. You're not fighting birds, weather, or forgetfulness — well, mostly not forgetting. Indoor sowing gives you a longer growing season, which means taller, more impressive flower spikes.
Let me break down the options so you can decide what works best for your situation. I use this little comparison every spring to make my choice. If you want to grow delphiniums from seed with the highest success rate, indoor sowing is the way to go. But direct sowing has its perks too, especially if you hate dealing with seed trays and hardening off.
| Method | Germination Success | Best For | Common Challenges |
|---|---|---|---|
| Indoor Sowing | About 80-90% with fresh seed | Cold climates, early blooms, rare varieties | Requires lights, space, and hardening off |
| Outdoor Sowing | Around 40-60% depending on weather | Mild climates, low-maintenance gardens | Vulnerable to slugs, birds, and heavy rain |
If you start indoors, plant seeds about eight weeks before the last frost. If you're direct sowing, wait until after the last frost has passed and the soil is workable. I prefer starting indoors because I'm impatient and want to see progress. Plus, I love babying the seedlings through those last chilly weeks of spring. It gives me something to do while I wait for the garden to wake up. For growing delphiniums from seed, indoor sowing is the safer bet, but outdoor sowing can work if you're feeling lucky and have mild weather.
How to Plant Delphinium Seedlings
Photos provided by pixabay
Hardening Off and Transplanting the Right Way
Hardening off is just a fancy term for "toughening up." You can't just throw a pampered seedling outside. It will go into shock. I lost an entire tray once — complete disaster. I left them out in full sun on day one, and they all flopped over like sad little noodles.
If you want to know how to plant delphinium seedlings correctly, hardening off is the absolute key. I don't think enough people take this seriously. You can't just take a seedling that has lived its whole life in a perfect 70-degree room and throw it into a windy, sunny garden. That's a recipe for transplant shock, and the plant will struggle for weeks. I learned this lesson the hard way when I lost half my seedlings in one afternoon. Now, I start the process about a week before I plan to transplant. I put the trays outside in a shaded, sheltered spot for just an hour or two on the first day. Each day, I increase the exposure by an hour and move them into slightly more direct light. By day seven, they're staying out all night. Planting delphinium seedlings this way builds tough, resilient plants. They'll have thick stems and dark green leaves — the kind of plants that barely notice the transition. When you do finally put them in the ground, water them in well with a liquid seaweed solution to minimize stress. Space them at least 18 inches (46 cm) apart. I know it looks empty at first, but trust me, they'll fill out. Better spacing means better air circulation, which means less mildew. And delphiniums are mildew magnets.
Soil Preparation and Feeding Your Young Plants
Delphiniums are heavy feeders. They love rich soil. Before planting, I dig in a generous amount of compost or well-rotted manure. Your plants will thank you with taller spikes and deeper colors. This is not a plant you can neglect and expect miracles from.
I once planted straight into my native clay soil without any amendments. Worst mistake ever. The roots just sat there in a puddle, and the plants barely reached 3 feet tall. Now, I always do a simple soil test before planting delphinium seedlings. These plants prefer a slightly alkaline to neutral pH (about 6.5 to 7.5). If your soil is acidic, add a little garden lime. If it's heavy clay, work in some sand or coarse grit to improve drainage. I'm not a fan of synthetic fertilizers right off the bat — the compost provides a slow, steady release that builds strong roots. After they're established, use a liquid flower fertilizer every couple of weeks. It makes a huge difference in the depth of color and the height of the flower spikes. Think of feeding as the secret weapon for 6-foot giants. I have a personal rule: I feed them once when the flower spikes start to emerge, and again right after the first bloom fades. This keeps the energy flowing and encourages that second flush of flowers later in the season.
Common Delphinium Growing Mistakes and How to Avoid Them
Overwatering and Poor Drainage
How many times have you killed a plant with kindness? For delphiniums, the #1 killer is overwatering. These plants hate sitting in wet feet. This is the most common mistake I see in forums and garden groups.
I've done it myself. You see the leaves drooping and think, "Oh no, it's thirsty!" and you water it more. But drooping leaves can also mean root rot from too much water. Think about where delphiniums come from — mountainous meadows with well-draining, rocky soil. They don't sit in bogs. Delphiniums need consistently moist soil, but it must be well-draining. If your soil is heavy clay, amend it with sand or grit, or grow them in raised beds. A good rule of thumb: stick your finger an inch into the soil. If it feels wet, wait another day. If it's dry, then water deeply. You want to encourage the roots to go deep, not just hang out at the surface. When you are growing delphiniums from seed, this is especially important because young seedlings are extremely prone to damping off — a fungal disease that thrives in wet, cold conditions. Use a well-draining seed starting mix and water from the bottom to keep the tops dry. Trust me, your delphiniums will be much happier if you err on the side of underwatering rather than drowning them.
Photos provided by pixabay
Hardening Off and Transplanting the Right Way
Here's a scene you don't want: a massive thunderstorm hits, and your 7-foot delphinium spikes are snapped in half on the ground. It happens to everyone who skips staking. I've seen it happen to neighbors who thought staking was 'ugly.' A snapped stem is uglier.
Imagine a 6-foot tall plant covered in heavy flowers. Now imagine a summer thunderstorm rolling through your yard. It's a disaster waiting to happen. I use bamboo canes or metal ring stakes. Put the stakes in early, when you transplant the seedlings. If you wait until the plant is fully grown, you risk spearing the roots or stems. Individual spikes can get incredibly top-heavy with those flowers. Tie the stems loosely to the stakes using soft garden twine. Don't tie them too tight — you want room for the stem to thicken up. It's a five-minute job that saves you from a heartbreak of a cut flower garden. Honestly, it's just part of the delphinium routine. I use a grid system now — a few bamboo stakes with twine woven between them creates a support web that catches the stems as they grow. It's almost invisible and handles the weight beautifully. If you're growing delphiniums from seed for the first time, don't skip this step. You'll thank yourself come August when the storms hit and your flowers are standing tall while your neighbor's are flat on the ground.
Delphinium Care Through the Seasons
Managing Pests and Diseases
What's the point of beautiful flowers if they're covered in black spots or being eaten alive by slugs? Exactly. You have to stay on top of this. These plants are magnets for all sorts of garden troublemakers.
Slugs and snails are the biggest enemies of young delphiniums. They will decimate a seedling overnight. I use organic slug pellets or beer traps early in the season. I also go out every morning with a flash light and a bucket of soapy water to pick them off by hand. It sounds gross, but it works. Later on, powdery mildew becomes a problem, especially in humid climates. To prevent it, water the soil, not the leaves. Give them plenty of space for airflow. If you see mildew, act quickly. A spray of milk diluted with water (1:10 ratio) actually works well as a preventative. Don't ignore it — the mildew can weaken the plant enough that it won't bloom next year. Japanese beetles can also be a problem. They love the tender new growth and the flower buds. I knock them into a bucket of soapy water every evening. Healthy plants are naturally more resistant. Keeping them fed and properly spaced goes a long way toward preventing major outbreaks. When you're growing delphiniums from seed, you're starting with clean, healthy plants, which gives you an advantage over buying stressed nursery stock. Use that advantage by keeping your garden clean and watching for problems early.
Encouraging a Second Bloom
Here's the pro tip: cut the spent flower spikes down to the base right after the first flush of flowers fades. You don't have to be gentle — just snip them off. Most people treat delphiniums as a one-and-done plant, but they don't have to be.
If you cut them back hard and give them a dose of liquid fertilizer, delphiniums will often produce a second, smaller flush of flowers in late summer or early fall. It's like having a bonus season. I always do this with my "Pacific Giant" series, and I get a nice show in September. Just make sure you don't let them go to seed, or the plant will think its job is done for the year. Also, leave some of the basal foliage in place — the plant needs it to gather energy for next spring. This technique reliably extends your bloom time by weeks. After the second bloom, I cut them down to about 6 inches above the ground and mulch heavily for winter. In colder climates (Zone 4 and below), you might want to add an extra layer of straw or leaves to protect the crown. When spring comes, remove the mulch and watch for new growth. The whole cycle starts again. Growing delphiniums from seed and getting them to rebloom in the same season is incredibly satisfying. It makes all the careful watering, staking, and feeding feel completely worth it. You'll be the talk of your garden club when you show up with delphinium bouquets in June and again in September.
Getting the Soil and Timing Right for Seedlings
Photos provided by pixabay
Hardening Off and Transplanting the Right Way
Here's a fun fact that most people miss: The pH of your soil actually affects the color of your delphinium blooms. I didn't believe it until I tested it myself, but it's true — at least to some degree. Alkaline soil tends to produce richer, deeper blues, while acidic soil pushes flowers toward pinkish tones. That's a big deal if you're chasing that classic electric blue.
I once grew two identical "Blue Bird" delphinium plants — one on the east side of my garden with neutral soil, and one on the west side where I'd been mulching with pine needles for years. The difference was subtle but real: the west-side plant had flowers with a faint lavender blush instead of the deep royal blue I expected. That's when I started paying attention to pH in my growing delphiniums from seed routine. You can adjust this before they even go in the ground by testing your soil and adding lime if needed. I aim for a pH of 6.8 to 7.2. I mix a handful of garden lime into the planting hole of each seedling before transplanting. Don't overcorrect, though — delphiniums can handle some variance, and adding too much lime can lock up other nutrients. If you're planting into pots, use a quality potting mix and check the bag for pH levels. Most commercial mixes are slightly acidic, around 6.0 to 6.5, which is okay for general growth but not ideal for peak blue color. You can add a teaspoon of hydrated lime per gallon of potting mix to bump it up. I do this every time I pot up delphinium seedlings, and I see a visible difference in the depth of color compared to plants in plain mix. It's a tiny extra step with a huge payoff.
Light and Temperature During Germination
Why do your delphinium seeds sometimes feel like they're napping instead of growing? The answer is almost always temperature. These seeds don't just want cold — they also need the heat to be just right after they come out of the fridge. I've found that 65 to 70°F (18 to 21°C) is the sweet spot.
After stratification, delphinium seeds need consistent warmth and some gentle light to poke through. But here's the thing — light is actually a trigger for germination, so don't bury the seeds deep. I press them lightly into the surface of the seed starting mix, just enough so they're held in place, and then I leave them uncovered or barely covered with a dusting of vermiculite. A seedling heat mat is worth the investment if you're serious about growing delphiniums from seed. I use one set to about 68°F, and I get sprouting in 10 days without fail. Without heat, it can take three weeks or more. Too much heat is also a problem. If the tray sits in a windowsill with direct sun streaming in, the soil can hit 85°F, and the seeds will just cook — they stop germinating entirely. I had that happen once when I left a tray on a south-facing counter during a warm spell. I came home to bone-dry mix and zero sprouts. Now I keep my trays under fluorescent shop lights in my basement, about 2 inches from the tubes, and I check the soil temperature with a simple probe thermometer every other day. Bright indirect light and a consistent 68 to 70°F give me the most reliable results. You'll see the first tiny cotyledons push through within two weeks, and from there, it's full speed ahead to your first set of true leaves.
How to Plant Delphinium Seedlings Like a Pro
Handling Root Systems with Care
Here's something I wish someone had told me years ago: delphinium seedlings have a taproot that doesn't like to be messed with. If you catch them too early or wrong, you'll stunt the whole plant. I lost an entire batch of 20 plants once because I was too rough when separating a clump.
The taproot is a single thick root that shoots straight down, and if you damage or pinch it during transplanting, the plant will never reach its full height potential. I learned this after a particularly rough transplant session where I separated a tray of crowded seedlings by pulling them apart like I do with tomatoes. The delphiniums barely grew 3 feet tall that summer, and the flower spikes were thin and wimpy. Now, I start each seed in its own small pot to avoid root disturbance entirely. If you're using a shared tray, use a butter knife to carefully lift each seedling with a generous plug of soil around the roots. Try not to handle the stem — always hold a leaf or the soil ball. Handle it like you'd handle an expensive cheese: gently, and with purpose. If you are planting delphinium seedlings from a community tray, wet the soil well before you start so it holds together. Then use a small trowel or a chopstick to loosen the roots. The fewer roots you break, the faster the plant establishes in the garden. I now use 4-inch pots for each seedling, and I skip the tray method entirely. The extra potting mix and space cost a few dollars, but the difference in plant quality is massive.
Spacing and Companion Planting Tips
You need space. And I mean real, generous space. At least 18 inches between plants, and if you're in a humid area, go for 24 inches. Delphiniums that can't breathe get mildew on every leaf. It's a fight you don't want.
I once crammed three delphiniums into a 3-foot wide bed because I was impatient and wanted a dense flower show. It looked amazing in June — then July humidity hit, and every single leaf had powdery mildew by August. The plants looked terrible, and the second flush never came. Now I treat spacing like a rule, not a suggestion. When you figure out how to plant delphinium seedlings, consider what you'll put around them. They grow tall and upright, so I like to underplant with lower-growing perennials like catmint (Nepeta) or lady's mantle (Alchemilla mollis). These cover the bare stems at the base of the delphinium, suppress weeds, and add texture. Catmint blooms purple-blue too, so it creates a nice color gradient. Avoid planting delphiniums next to other heavy feeders like roses or peonies — they'll compete for nutrients. Instead, pair them with plants that like similar conditions: moist, well-drained soil and full sun. Foxgloves, lupines, and campanulas all fit the bill. And here's a weird trick I use: plant a few marigolds nearby. They attract beneficial insects that eat aphids, and the scent confuses pests looking for delphiniums. It's not a silver bullet, but it reduces the need for sprays. With good spacing and thoughtful neighbors, your delphiniums will be healthier and more impressive.
Common Delphinium Growing Mistakes and How to Avoid Them
Ignoring the "Crown Rot" Danger Zone
What's the sneakiest thing that kills established delphiniums? Crown rot, without a doubt. It's not as obvious as slugs or mildew, but it's far more destructive. You usually notice it when the plant collapses mid-season with a split at the base.
I have a friend who grows delphiniums in a gorgeous English-style border, and she lost three of her prize-winning "Pacific Giants" in one July. The plants looked fine, then suddenly the stems flopped over. When she dug them up, the base was mushy and brown. That's crown rot, caused by a fungus that loves wet soil that sits around the stem crown. The mistake most people make is planting too deep. When you are growing delphiniums from seed, the crown — where the stems meet the roots — needs to sit right at or slightly above soil level, never below. In heavy soil, I actually create a small mound or raised ridge using gravel or coarse sand around each seedling's base to keep water from pooling against the crown. The single best preventive step I know is making sure you don't contribute to crown rot through poor drainage. Also, make sure you clean up any dead leaves in fall. The fungus can overwinter on plant debris. I lost two plants last year from simply forgetting to remove the old stems after the first frost. Now, in late autumn, I cut each plant down to about 4 inches and toss all the trimmings in my yard waste bin, not the compost pile. Crown rot can survive in mulch, so don't add infected material to your compost. It's a simple clean-up routine that saves you from heartbreak in spring.
Not Replacing Plants Often Enough
I'll be blunt: delphiniums are not perennial in the way peonies are. They can be short-lived. After about three years, even the healthiest plants start to decline. A lot of gardeners let them languish instead of starting fresh from seed.
Every good guide on growing delphiniums from seed should warn you about this. The plant's root system gets woody and old, flower spikes get shorter, stems get thinner, and color starts to fade. I used to think I was being wise by keeping my plants for five or six years, layering compost every spring and hoping for the best. But their performance dropped noticeably after the second year. The third year was a sad, pale imitation of the first. Now, I start new delphinium seeds every single year, even if my old plants are still going okay. That way, I always have a batch of vigorous first- or second-year plants ready to replace the aging ones. It's the same approach professional rose growers use — they keep a rotation of young stock. If you propagate from seed every year, you also keep genetic diversity, which makes your whole garden more disease-resilient. You don't have to tear out the old plants immediately. Plant the new seedlings nearby, and as the old one fades, cut it down and let the new one take over. This continuous cycle means your flower border always has peak-performing delphiniums, and you never experience that disappointing lull.
Delphinium Care Through the Seasons
Winter Protection Strategies for Colder Zones
If you live in zones 3 to 5 (or even zone 2 in a sheltered spot), winter is the real test. Delphiniums don't always survive harsh winters. I'm in zone 5, and I've lost good plants to freeze-thaw cycles that heave the crown out of the ground.
Here's what I do every fall after a hard freeze kills the top growth. I cut the stems back to about 6 inches. Then I pile a thick layer — about 4 to 6 inches — of loose straw or shredded leaves over the crown. I top it with a layer of evergreen boughs or brush to hold the mulch in place against wind. One key point: do not use packed-down leaves or heavy mulch, because that can trap moisture around the crown and invite rot. Airy insulation is the goal. In late winter, I remove the boughs and gently rake away the straw so the crown gets light and air as days get warmer. This happens anytime between late February and late March, depending on your local weather. I watch for the first green shoots appearing at the base — once I see them, the mulch has to come off quickly. I also purposely plant delphiniums in raised beds or slopes so winter water drains away from the crown. If your soil is clay, a raised bed can make the difference between survival and death. Growing delphiniums from seed and getting them through their first winter is a huge milestone. Treat the crown with care, and your plants will reward you with years of tall blooms.
Dividing and Propagating for Longevity
Instead of letting your plants get old and woody, you can divide them every two to three years. It's a way to rejuvenate the clump and get more plants for free. But be careful — older plants don't like their roots disturbed too much.
I divide my delphiniums in early spring when I see about 2 inches of new growth. I dig the entire clump up, fingers crossed that the crown isn't too tangled. Then I use a sharp, clean spade to cut the clump into sections, making sure each section has at least two to three healthy shoots and a good chunk of root. I replant these at the same depth they were growing, spacing them as if they were new seedlings. The new divisions take a while to establish, but by midsummer, they produce impressive spikes. This method works well if you have a favorite variety and want to keep its lineage going without buying new seeds. However, I recommend this as a complement to growing delphiniums from seed, not a replacement for it. Division keeps your garden full quickly, but seed-grown plants often have more vigor in the long run because they build a fresh root system from the start. I personally run a mix of both: I start seeds every spring for genetic strength, and I divide my best established clumps every third year for insurance and quick fill. If you have a particularly stunning bloomer, propagation by division preserves that exact plant's genetic makeup. Seeds from the same plant can vary quite a lot. Keep both strategies in your gardening toolkit, and you'll never run out of tall, gorgeous delphiniums.
E.g. ：How to Grow Delphinium Flowers From Seed - YouTube
Growing Delphiniums From Seed - Good Soil Nursery
How to Plant and Grow Delphinium from Seed - YouTube
How to Plant Delphinium Seeds - Eden Brothers Planting Guides
How to Grow Delphinium From Seed - YouTube
FAQs
Q: Why won't my delphinium seeds germinate — what am I missing?
A: This is the most common frustration I see when people start growing delphiniums from seed. The number one reason for failure is skipping the cold stratification step. I made this exact mistake my first time — I planted them like tomatoes and got absolutely nothing for weeks. Delphinium seeds need a cold period to break dormancy. Without it, they just sit there. Pop your seeds in the refrigerator for a full week before planting. I put them in a sealed bag with a damp paper towel. Don't skip this step. Another big issue is planting them too late. Start seeds indoors about eight weeks before your last frost. Even if you use perfect soil and water faithfully, if you miss this timing, the plants won't have enough energy to produce those 6-foot spikes. Also, make sure your seed is fresh — delphinium seeds lose viability fast. If you're buying from a nursery, check the pack date. Old seeds will give you spotty germination at best. I've had nearly 90% success with fresh seed versus barely 30% with old seed.
Q: Should I start delphinium seeds indoors or outdoors — which is better?
A: I always recommend indoor sowing for growing delphiniums from seed if you want the best results. You get way more control over temperature, moisture, and pests. I start mine indoors about eight weeks before the last frost, and I get around 80-90% germination with fresh seed. Indoor sowing gives you a longer growing season, which means taller flower spikes and earlier blooms. Outdoor sowing works too, but you're at the mercy of weather, birds, and slugs — germination drops to about 40-60%. I only direct sow when I'm feeling lazy or if I have extra seed. If you do sow outdoors, wait until after the last frost and keep the soil consistently moist. Cover the seeds with about an eighth of an inch of soil. The real benefit of indoor sowing is that you can baby the seedlings through those tricky early weeks. You can control light, temperature, and humidity. Plus, you avoid damping off, which is a fungal disease that kills young seedlings in wet, cold soil. I've lost entire trays to damping off when sowing outside in a rainy spring.
Q: How much space do delphiniums need — and do they need special soil?
A: Yes, these plants are picky about soil. When planting delphinium seedlings, space them at least 18 inches apart. I know it looks empty at first, but they fill out quickly. Crowded plants get powdery mildew, and you don't want that. For soil, delphiniums are heavy feeders. They need rich, well-draining soil with a pH between 6.5 and 7.5. Before planting, I dig in a generous amount of compost or well-rotted manure. If your soil is heavy clay — like mine was — add sand or grit to improve drainage. Standing water is a death sentence for these plants. I learned that the hard way when I planted straight into clay and got stunted 3-foot plants instead of 6-foot giants. Do a simple soil test before planting. If your soil is too acidic, add garden lime. If it's too sandy, add organic matter to hold moisture. After they're established, feed them every couple of weeks with a liquid flower fertilizer. It makes a huge difference in flower spike height and color intensity. Think of feeding as your secret weapon for those Instagram-worthy blooms.
Q: How can I get taller, stronger flower spikes from my delphiniums?
A: The secret to towering flower spikes is a combination of three things: proper staking, heavy feeding, and deadheading. First, put stakes in early — when you transplant the seedlings. I use bamboo canes or metal ring stakes. If you wait until the plant is fully grown, you risk damaging the roots. Tie the stems loosely with soft garden twine, leaving room for growth. Second, feed them well. Delphiniums are heavy feeders. I apply compost at planting time, then use liquid flower fertilizer when the flower spikes start to emerge and again after the first bloom fades. This keeps energy flowing for that second flush. Third, cut spent flower spikes down to the base right after they fade. This tricks the plant into thinking it needs to bloom again. I reliably get a second, smaller bloom in late summer or early fall using this technique. Also, never let them go to seed — once they set seed, the plant thinks its job is done. With the right care, you can get spikes over 6 feet tall. It's incredibly satisfying watching them tower over the rest of your garden.
Q: What's the best way to overwinter delphiniums — will they come back next year?
A: Absolutely, delphiniums are perennials, and with proper care, they'll come back bigger and better each year. Here's my winter routine. After the second bloom fades in fall, cut the stems down to about 6 inches above the ground. Leave some of the basal foliage — the plant needs it to store energy for next spring. Then mulch heavily with straw or leaves, especially if you're in a colder climate like Zone 4 or below. I add an extra layer of leaves on top of the mulch for insulation. In spring, remove the mulch as soon as you see new growth. Don't rush this — cold snaps can damage tender new shoots. Delphiniums are hardy to Zone 3, but they need protection from wet winter soil. Good drainage is critical. If your soil stays soggy over winter, the crown can rot. I've lost plants to winter rot more than once. To prevent it, plant them in raised beds or on a slight slope. Also, divide mature clumps every three to four years to keep them vigorous. Old clumps get woody and produce fewer flowers. When you divide them, replant the healthiest sections with fresh compost. With this care, your delphiniums will reward you with spectacular blooms for years.
