Delphiniums, family and fun

Wednesday, June 11, 2008


At this time of year, when northern hemisphere gardens have delphiniums either blooming or heading that way gardeners often write with questions about how well, or not, their delphiniums are growing.

Usually they have been growing well but as the flower spikes reach, say a metre tall, we begin to get reports of lower leaves dying, or a paleness of colour in the leaves or maybe short, thin stems. What is causing all this? Is the question, and how do I fix it?

I thought it may be a good idea to run through a few common problems and their cures, for the benefit of any reading this blog who may like to know.

It will help to list those conditions that delphiniums like and to also tell you that they are gross feeders. Not gross feeders as in gluttonous individuals eating a hundred and forty four giantburgers in the minimum time possible and slopping tomato sauce over a “once white” tee shirt t-shirt; no, not at all. There’s a big difference. Delphiniums don’t like hamburgers, or tomato sauce for that matter. What they do like however is plenty of food, particularly when they first begin new growth. They like plenty of NPK. Go more heavily on the nitrogen at the start, gradually easing off and putting more emphasis on the potash as the stems grow tall and the buds begin to form. If you have access to animal manure you probably won’t be able to give them too much no matter how hard you try. If you are relying mainly on chemical fertilisers then using a 12-10-10 fertiliser at rates just as much as you dare will give great results. As a rule of thumb feed delphiniums about 1 ½ times what you would feed your roses.

Be sure your soil ph is above 6 and preferably closer to 7. If not add lime, lots of it.

Delphiniums also like that ideal type of soil that most growing books and planting instructions demand ......well drained, holds lots of moisture, doesn’t dry out too quickly, doesn’t go puggy and get too wet, not too fine, not too course and obviously after all this, it should be covered in at least 2 inches of good, rich, brown, friable organic mulch. If your soil is like this then I’ll send a truck right over. If not then just be sure that the ph is high, the plants don’t get waterlogged and they have plenty of tucker, plenty of tucker, plenty of tucker.

If mulching, make it thick. If mulching with wood products then be sure to add more nitrogen.

Delphiniums like lots of sun so give them plenty of room in a sunny spot.

Delphiniums do not like lots of heat so if your summer temperatures regularly exceed 25 degC then plant them in a position that gets afternoon shade.

Keep them damp, but not wet.

Place slug pellets (or sharp sand or something similar) on the crowns to deter slugs and snails.

Remember, feed them often and well, water them often and well, sing to them often and well and to enjoy them. If you can’t sing well – practice.

Beware of the wind. Delphiniums are a bit like you, they enjoy a good steak and remember, if your delphiniums don't look like these you need to give them more fertiliser. If they still don't perform, buy some of our seed. You will really see the difference.

Take care. Have a great time in the garden.

1 comment:

KL said...

Hi Terry,
Haven't visited your blog for a few months. Glad I finally did! This post about the hunger of delphiniums was great. I now have 82 little ones growing in 4" pots behind my greenhouse. My friend Sue has the other 82. I grew all of these from 4 packets of seed that Sue purchased from you last September.

The plants were seeded in early March and now, after transplanting, they have about 4 true leaves of a massive size!

We've had a very wet spring and the D's didn't like that at all. But the weather is warming up and drying out and they're perking up and starting to grow! Tonight, after reading your post, I put 1/4 tsp of Osmocote into each pot to ensure they don't go hungry between feedings of a more organic nature.

I see you have linked to our blog from your website ( Thanks very much for doing that. David and Ann and I are having fun with it.
Warm good wishes from Vermont,
Kathy LaLiberte