Lin's Plant Files: Delphinium

My experience:

I think delphinium (aka larkspur) is one of the most beautiful flowers of summer, and it is available in so many amazing colors.  It is one of my current favorites.  I bought some seeds on a whim, despite having no idea where I would put them.  The majority of my yard is shady, and I knew delphs liked sun.  I finally spread the seeds along the side of my garage and around the back corner.  I like growing tall flowers along a wall, and this area gets more sun than most other places I had available.

I will readily admit that I did everything wrong with these seeds and put in very little effort.  I didn't give the seeds any cold treatment before planting.  I put them out in late May, weeks later than I would consider ideal.  I didn't till the ground, I just threw the seed down, sprinkled a little potting mix on top, and watered.  I watered the area when I thought of it, but certainly not regularly.  I let weeds grow up around the area, because I wasn't sure what the plants would look like when they appeared. 

I eventually scoured the Internet and came up with a few pictures of delphinium seedlings, so I at least knew what to look for.  And lo and behold, a few weeks ago I noticed some small plants with the characteristic lobed delph foliage.  I don't have nearly as many as I had hoped for with the amount of seed I put down, but I am holding on to some hope that after laying around in the cold this winter, perhaps next spring I will have some more plants popping up.

Here is a pic of one of my little seedlings:

I guess I am just lucky.  By all accounts, my delphs shouldn't have survived my haphazard planting.  They are pretty small, only about 6 - 8 inches tall right now.  Since they came from seed, it will take a while for them to reach full height.  And they may never be huge in their partially shady spot.  But against all odds, I have blooms in the first growing season - which doesn't usually happen unless you winter sow or start the seeds inside very early, which I did not. The first bloom is small but so gorgeous.  Here is a pic:

Pictures don't really do this baby justice.  It is a deep purple with blue streaks, and it is really gorgeous.  I haven't taken the time yet to try and figure out what kind it is - I planted several varieties, all in shades of blue, purple, and white.  But I am thrilled to see these little blossoms.  I have a couple more small purple ones blooming, and several with buds that haven't opened yet. 

Since I have become very fond of these flowers this summer and have been waiting impatiently for them to grow, I did a little more research.  I may need to plant more next year.  So if you would like to know more about growing delphinium, the right way instead of using my crazy method, read on.

How to get started:

You can buy delphinium plants and put them in your garden.  This is the fastest way to get large blooming plants.  It is worth noting that many people report that mature delphs don't like being moved, so you may have to baby them a little if you go this route.  Delphinium can also be propagated by taking cuttings from mature plants and rooting them.  This is only recommended if you are experienced at taking and rooting cuttings, as they may not root as easily as other plants.  The third option is to purchase seed and grow them from scratch.  

Growing from seed:

I have seen a lot of gardening message boards with people lamenting their inability to get delphinium seeds to germinate.  It seems a lot of those who do succeed winter sow their seed.  If you don't know how to do this, look it up or wait for me to get around to writing about it (yes, it's on the list).

Not everybody likes winter sowing, so you can try stratifying and planting.  First, delphinium seeds must be fresh.  They lose their vitality after a year.  Your best bet is a supplier, especially if you want a particular color, as garden seeds may be hybrids.  Next, they do need to be stratified.  I know, I didn't stratify mine and they came up.  But I was lucky.  We had a cool spell a week or two after I put the seed out, and that is probably the only reason any of mine germinated.  My germination rate wasn't great.  To stratify, you need to put some potting mix in a baggie, dampen it slightly, and add the seeds. Label the baggie if you want to know what type of seeds are in there.  Put the baggie in the fridge, and check it every week or so.  The soil needs to stay moist, and you want to watch for germination - root tips or plants sprouting.  If you want more in depth info about stratification, check out my post about growing roses from seed.  It's the same process.  Some people put their seeds in the freezer for a day or two before stratifying.  It may be worth a try if you have had trouble germinating delphs in the past.

Delphs need to be stratified for at least a couple of weeks, and they need cool dark conditions to germinate.  I would leave the seeds in the cold treatment until you see germination, but if it has been several weeks or you are just too impatient, make sure to put your planted seed tray in a cool, dark location until you see growth.  You will want this location to be warmer than your fridge, though - around 65-70 degrees.  Move them into the sun as soon as you see sprouts.

Plant your seeds in a seed tray, or if it is late spring & the seeds are germinating, plant them outside.  Seeds need to be covered shallowly and kept moist.  First year plants usually don't bloom unless they are started inside very early.

Growing needs:

Delphiniums like rich, well draining, neutral to slightly higher pH soil.  They don't like having wet feet in winter, so modify your soil if you need to.  Adding a small amount of lime to your potting medium or soil may be beneficial.  Delphs need plenty of water during their heavy growth period - usually May - July, so be sure to water them if Mother Nature is slacking.  Don't overdo it, or you may end up with crown rot.  But don't let them go thirsty, either. 

These plants are also heavy feeders - they will need to be fertilized often throughout the summer.  A liquid fertilizer is probably best for these beauties, since it will be immediately available to the plant.  Liquid fertilizer can usually be applied every couple of weeks.  Be careful not to overdo nitrogen - liquid fish emulsion is suggested as a good option for fertilizing.

Delphiniums like plenty of sun, but they may tolerate partial or dappled shade.  Especially if you live in an area with intense summer heat.  My baby delphs are probably only surviving and blooming because they get some shade during these oppressive days of IL summer.  So take your climate into account when you choose your planting site, because your babies will go dormant or even die off if they get too hot.

You can get delphs in small sizes that only grow to about a foot, all the way to the giant breeds that stand 6 feet tall.  If you have the taller varieties, they will need to be staked.  Using 4 stakes to create a cage is a great way to keep them from falling over.  You can tie the lower part of the plant to a stake, about a foot from the ground.  Further up, you will want to tie more loosely to allow some movement, or the spike will break off in the wind.  This is why a cage setup is sometimes best.  Make your last tie just under the bottom spike. 

 
Dividing:

Plants that are getting crowded need to be divided.  For delphinium this is about every 3 years or so.  Making sure to divide and spread out your plants will help them last longer in the garden.  Dig up and carefully divide in the early spring, just as the first shoots are starting to emerge.  Each piece needs plenty of roots and at least one strong stem.  When you replant them, the crown should be about 2 inches under the soil.

Spike culling:

For healthy plants, you don't want too many spikes.  First year plants usually only have one flower spike.  Second years can handle three, and older plants can have up to five.  As the plant begins to put out spikes in the spring, select the spikes to keep and cut off the rest.  Older plants will produce more spikes. But too many spikes will deplete the plant and make it unhealthy, and crowding promotes fungal problems.  I know it's hard to cut off those potential blooms, but it really will make your plant healthier.

Pests:

The biggest pest problem comes from slugs.  Crushed eggshells around your planting area may help, or sinking a partially full beer can into the ground near your plants to act as a trap.  Slugs can take out your entire delph population, so take the threat seriously.

Diseases:

Keep an eye out for powdery mildew, black spot, and crown rot.  Treat with an anti-fungal if necessary.  Keeping your plants uncrowded and free of weeds will allow better air circulation, which in turn will cut down on fungal diseases.

Fall care:
When blooming is done, cut the spike off the plant.  It may rebloom in late summer or fall.  Allow the rest of the plant to stay and build up its food supply.  In fall, cut the plant to the ground and clear away all debris.  Slugs may take up residence and do a lot of damage if you leave the clippings laying around.  Also, spreading a little sand over the area will help deter them.
Life span:

Most delphinium will last about 3-5 years if kept healthy.  If you divide and replant as they spread, you should have delphs for many years.

Interesting facts:

Delphinium gets its name from the word dolphin, due to the shape of the bloom spike.  They are in the buttercup family.  The flowers can be used to make blue ink.  All parts of the plant are poisonous to humans & most animals if consumed, although it is thought that very small amounts can be used to treat asthma (but not sure I would try it!)

Good luck with your delphs & enjoy!