While I along with many others have dabbled with no dig methods of gardening, in truth I have yet to find anything that works better when establishing a new bed than digging the bed throughly over and incorporating a good amount of organic matter. This holds true for growing Kniphofia, where good preparation of the soil helps significantly helps in permitting a nice open and well drained soil structure – conditions which Kniphofia thrive in.
When it comes to when to plant Kniphofia , as herbaceous perennials, conventional wisdom holds true that Spring and Autumn are the best planting times. Of these two however, I have had the most significant success with spring plantings – with Autumn planted Kniphofia occasionally struggling through the following Winter. I chalk this up to Spring planted Kniphofia simply having a longer season to grow and bed in before having to face the daunting winter cold and wet. Autumn plantings do work well though for larger plants.
Having decided when to plant your Kniphofia and prepared your soil the next question is how to actually plant it. Conventional wisdom tells us that when planting a herbaceous perennial it should be planted at the exact depth it was in the pot. But is that the best advice for Kniphofia? This all depends upon who grew the plant, in general though I have found that Kniphofia are very commonly planted too deep in pots!
If these plants are planted out at this exact height, while they may well be ok for a season or two, I find that increasingly such plants are at risk of crown rot – resulting in failure to thrive or death of the plant if left unchecked.
Through a process of trial and error, I have found that the optimal Kniphofia planting depth is to have the woody crown of the plant slightly proud of the soil surface – akin to how bearded Irises are planted. By planting at this depth you are actively removing the susceptible portion of the plant from the soil. This also encourages more stems to grow by exposing the crown to light.
The only caveat of this method is winter cold. Kniphofia in extreme winters can succumb to the cold and die. I have found however that the old leaves typically form a natural insulating layer for the crown, protecting it from all but the most severe cold – in which even deeply planted plants could succumb anyway!
I advocate that before planting out a Kniphofia, it Is important carefully inspect the base of the plant. Can you see the crown? Is it just a mass of leaves arising from the soil? If so always begin by stripping away the upper layer of soil until the crown or base of the stems are exposed – sometimes plants are not yet old enough to have developed a noticeable woody crown.
During this process you may well be removing some surface level roots but, in my experience, this does no harm to the plant. It is far better to ensure the Kniphofia is planted at the correct depth than worrying about a few lost roots! Only once you are happy that you have exposed the crown should you dig a hole for the plant.
Dig a hole just deep enough to ensure the crown sits slightly proud of the soil. Double check the crown is not buried, add a little grit to the base of the planting hole if planting in a heavier soil and carefully bring back the soil and firm in well, ensuring the plant cannot rock in the wind.
Then give the Kniphofia good water, taking care not to unduly soak the crown. Keep the plant relatively well watered for the first couple of months – a good soak once a week should suffice. Once settled into the new bed, slowly taper down your watering to encourage the plant to find its own water source. Once established and mature, Kniphofia need little to no additional water.
Aftercare cultivation tips
Just because your Kniphofia is now planted at the correct depth, crown proud, and growing well your job is not done! Every Spring there is work to do to ensure your Kniphofia stays healthy! Typically Spring is the time of the year where mulching is the most important job in the garden. With Kniphofia though take care!
Having taken so much effort to ensure the plant crown is not buried don’t undo this good work by burying the plant in mulch, instead leave a good circumference around the plant un-mulched as a precaution against crown rot. Other important Spring jobs for Kniphofia include giving them a generous handful of your favoured fertiliser and tidying up the plant by removing all dead or dying foliage. Such foliage will be immediately obvious, being brown/yellow and dry or slightly mushy.
As this dead foliage is unsightly, removing it immediately improves the appearance of plants but more importantly by removing this dead foliage you are both removing a hiding place for slugs and snails and also removing a potential source of rot – rot which could well spread into the crown later in the year.