NPK values for chilli plants

We humans are fussy eaters. Chillies are not. Chillies will take whatever meal you throw at them and, feast-or-famine, they will still grow, flower and fruit. Mostly.

However, the subtle science of feeding chilli plants well is a true art form that takes many a Summer to perfect. The variations of an ever-changing, seasonal menu for your chilli babies are as endless as Annabel Karmel recipes for troublesome toddlers. A good diet will hopefully produce a bounty of flavoursome, aromatic & glorious chillies to make your friends go oooh and ahhh. Much the same effect as when your young child selects an olive instead of a chicken nugget in front of an audience of NCT peers.

What does a chilli like to eat?

Let’s stick with the core ingredients for now: NPK, or Nitrogen, Phosphorus and Potassium to the uninitiated. Pretty much all feeds, fertilisers, composts, sprays, granules, enhancers, hydroponic potions contain these wonder components. As do most soils around the world. These macronutrients are the backbone of a good chilli plant diet. The most basic of fertilisers will provide an NPK ratio on its label. But just what are they and what do they do?

Nitrogen (N)

Why is Nitrogen necessary?

Think healthy leaves.

It is a key component of chlorophyll, the green stuff in plant cells. Chlorophyll uses sunlight to convert water and carbon dioxide into sugars as plant energy. Nitrogen is also a major component of protoplasm, the sappy contents of plants cells. Protoplasm is the vessel which holds trace minerals throughout the plant.

What does the correct supply of Nitrogen do to your plants? Healthy, green, lush plants. Strong stems and perky leaves. Speedy new shoots and flower bud formation.

What does the wrong balance of Nitrogen do to your plants? Too much Nitrogen will cause rapid growth, causing the plant to over commit. High Nitrogen feeds will inhibit flowering. Not enough Nitrogen and growth will be slow and the plant will end up stunted.

Traditional growers will add Nitrogen to their plants through blood meal, composted manure, composted coffee grounds. Blood meal is high in Nitrogen (12%).

Phosphorus (P)

Why is Phosphorus necessary?

It’s all about those roots and fruits baby!

Phosphorus is essential for plant cell division and development of new tissue. Think about when your chilli seedling is just getting going. All those new leaves, all that stem and root to grow, maintain and look after. Phosphorus is the ultimate support partner. It is in charge of seed development and as a result, timely flower formation, good sized and uniform fruit development and maturity.

What does the correct supply of Phosphorus do to your plants? Get the phosphorus levels right and you can expect strong early growth; plants reaching maturity earlier and roots showing through the bottom of the pot quickly. When potting on the first time, a good root system will be visible. It can also stimulate tillering, shoots springing from the bottom of the original stalk. making bushier plants.

What does the wrong balance of Phosphorus do to your plants? An excess of phosphorus in chilli plants can cause leaf issues, ending in leaf death. Too little Phosphorus and the plants may just not mature. In a few more detailed trials, it seems that less capsaicin and less fructose was found in plants that grew and fruited with lower levels of phosphorus. Not what is intended at all!

Bonemeal is high in Phosphorus (18%). Hoof and Horn is even higher (29%) Phospohrus is tricky to uptake, especially at low temperatures, low pH or in conditions with excessive iron in the soil.

Potassium (K)

Why is Potassium necessary?

Hearty growth and protection is the name of Potassium’s game.

Potassium regulates the closing and opening of stomata, and so can affect the amount of CO2 supply to the plant. CO2 is essential for photosynthesis and energy production. Low Potassium=low energy. Potassium plays a major role in the regulation of water movement within plants, in the roots and again the stomata. Essential transportation of nutrients, water and other minerals are also dependent on Potassium. Potassium is also a major player in cell wall thickening. This means that stems are stronger and all cells are less susceptible to disease.

Potassium has been proven to increase the likelihood of fruit setting in chillies. Not more flowers but definitely more fruit set.

What does the correct supply of Potassium do to your plants? Generally healthy plants with good tolerance to changes in environmental factors. Good drought and cold resistance in chillies. Allows fruit to develop and set well.

What does the wrong balance of Potassium do to your plants? A sad, stunted, yellowing plant will be on your hands if it is lacking in Potassium. More susceptible to drought, cold, pests as it will have thin cell walls. Less likely to grow quickly with strong stems. Waste products are not removed well, with yellowing of the leaves, ultimately ending in leaf drop. When seedlings first emerge they are vulnerable to damping off. Correct potassium levels at this stage can mean more seedings survive.

Potassium is linked to many growth enzymes in plants. Get the balance wrong and growth can be stunted. Too much Potassium may inhibit uptake of Nitrogen and Phosphorus as well.

Seaweed is a traditional plant treatment containing high Potassium. As is a more modern banana tea.

Is that it? Get the NPK value right and the chillies will be perfect?

Well, yes. And, no. Getting the NPK values balanced correctly for the plant’s needs at key points in the growing season is a huge, important task. BUT there are other factors too though. Other macronutrients (Sulphur, Magnesium and Calcium), micronutrients (Iron, Boron, Chlorine, Manganese, Zinc, Copper, Molybdenum and Nickel), micro-organisms, micro rhizomes, humidity, pH, pests, light levels, leaf quantity and size, pests, electronic conductivity of water, air flow and music choice.

The factors are myriad. Plenty more Googling to be done.

Homegrown Jalapeno chillies, the first of the season
Homegrown jalapeños, the first of the season

The science of feeding your chillies is in your hands. Maybe that weekly slosh of tomato feed needs rethinking?

Time to shed some light on the chillies

It’s that time of year where the sun is lovely & warm and the nights are not too chilly. We’re racing towards longest day: action stations everyone.

The Birdhouse greenhouse is brimming with leafy specimen. No longer a cocooned sanctuary from the Night King but a claustrophobic bubble isolating the chilli babies from the real world. Time for the babies to grow UP and for the bubble wrap to come DOWN. It has served its insulating purpose well but now it is shading a little too much; stopping the auto ventilation window doing its thing; trapping pollinators and taking up precious ceiling height. Roll it up for next year.

Suddenly, the whole space is flooded with clear light. Wonderful.

The light issue continues…

A quick stock take reveals that we are seriously running out of space. How this has happened is beyond us but it seems to be a phenomenon known well to Chilliheads across the land. Each season we go through a number of cullings. Precious plants are sorted into ‘keepers’ and ‘the rest’. And yet, despite this harsh practice, there still seem to be more pots than ever before.

We sorted at chitting/germination point. Some seeds just didn’t look right and didn’t get potted up into wee paper pots. The compost heap was the destination for these leggy seedlings. The next couple of rounds of sorting happened at potting on stages. Weedy plants, non-thrivers or just varieties where we had too many plants were all thinned out.

The thinnings will populate our local school Summer Fete’s plant stall. They have been potted into non-conformist pots that we do not wish to keep for re-use; kept outside in temperatures of nearly zero; unceremoniously plonked into multi-purpose compost and barely kept alive on a lean diet of fresh air and rain water. They are, however, tall and flowering away, so all is good. They should sell well!

And now, we should be at the point where the perfect number of plants has been achieved. And how many do we have? 110 to be exact. We couldn’t possibly manage with less that that number of plants.

110 plants and counting

But hang on a mo, there STILL doesn’t seem to be space for them all in the greenhouse. We are having to utilise the floor for trays of plants. This is not ideal as the light levels are lower down there. Rotation of plants is tricky but absolutely necessary. On top of the overcrowding issue, lots are yet to go into their final (bigger) resting pots. So after all that sorting there are still too many plants.

Family, neighbours and friends beware, you will have to adopt some chilli babies…Momma’s about to get mean.

Meanwhile, in happier news, some of the bigger, earlier fruiters are just getting on with their thing. Golden Greek Pepperoncini is smothered with flower and fruit. Oh, and the roots are out the bottom again. Time to reach for the soldering iron and make some holes in the bottom of those flower buckets because potting on is in the diary for the weekend AGAIN.

Begone Fiendish Frosts

UK frosts are a damnable thing…dominating our lives for weeks on end, with never the same frost twice. Omnipresent during the darker months. No way a chilli plant is growing out there…not a snowball’s chance in Hell.

In early Spring, just when the birds are a-nesting, Jack Frost STILL manages to sneak up on you at the most unexpected times. You assume he’s gone, but then, BOO, there he is again! In the air, on the ground, feathered across the windows, wiping out blossom and melting soft new growth left, right and centre. He’s a real pain in the backside.

Luckily things start to change: the mercury creeping up the thermometer gives us a glimpse of light at the end of the tunnel. This cold WILL NOT last forever, we CAN do this.

Some nights are mild, then back to cool, then a few nights are colder. Watch out for the occasional late season sub zero arctic blaster though. No predictability leaves us doing the dance of a thousand plants, in and out we go. In the hope to harden off but not kill off.

Suddenly, ta-dah, there are no more frosts and all is forgotten (and forgiven). We go forward to salad days.

In our corner of Hampshire, the second week of May is scheduled as the last frost this year- pah, as if it is that easy to predict! Still, it does seem the worst is over and we can finally get on with the task of growing some chillies. And growing they are….

All plants are in the greenhouse or outside. Feeding and watering when the leaves look droopy. A twice daily check for aphids and an invitation to a ladybird or two over for dinner if any ‘phids are found.

Buds aplenty, some flowers are open, a few chillies have set and most plants look pretty happy with life.

Long may it last.

Tangy Prawn and Coconut Curry

It’s a bank holiday weekend and we are cooking on an Aga. Life is pretty good. So, what to cook? OK, how about something with chilli? Sure thing!

It’s Aga time!

Gather and prepare the ingredients before you start as the cooking of this dish is fast and furious. Make your chilli and spice selection. Will it be chilli powder, fresh chilli, chilli paste, chilli flakes, chilli sauce, homemade spice mix, fermented chilli paste. In the ingredient list below is our choice. Go with whatever flavours suit your mood, palette and heat tolerance. The choice is all yours!

Choose wisely.
  • sunflower oil
  • 2 red onions, sliced
  • a spoonful of gochujang (such an amazing, yummy product, adding depth and umami to dishes like this)
  • 2 cloves of garlic, sliced
  • a thumb of ginger, peeled and grated
  • a chilli of your choice, sliced
  • small handful of garam masala (we ground our own for this recipe with coriander seed, cumin, fennel seed, white peppercorn, lots of cardamon, cloves and cinnamon)
  • a finger of fresh turmeric, finely grated
  • 4 tomatoes, chopped roughly
  • 2 tsp of runny honey
  • a handful of desiccated cocount
  • a can of coconut milk
  • bunch of coriander, chopped
  • a whole lot of prawns (100 g per person)
  • green pepper, sliced
  • pak choi, leaves and stems chopped
  • a lime for squeezing

Now you’re ready to cook up one tasty prawn dish.

  • Heat a wide pan, big enough to fit the entire dish in it. We opted for a 30cm almond Le Creuset shallow casserole, needs must and all that.
  • Add the sunflower oil and onion. Fry until the onions start to take on a little colour.
  • Add ginger, garlic, chilli and turmeric. Fry for 30 seconds. Don’t let the garlic burn now. That’s why we tend to slice garlic, not crush. Less chance of burning.
  • Add garam masala, gochujang, honey and tomatoes. Allow it all to smoosh together.
  • Now for the coconut. Chuck in the dessicated stuff and let it absorb the liquid from the tomatoes. Then give the can of coconut milk a good shake and tip it in. You might need to scrap the more solid part out if the can is cold.
  • Let the sauce come up to a bubble and thicken slightly.
  • Thrown in the peppers, pan choi stalks and the prawns.
  • When the prawns are pink, stir the pan choi leaves in and serve.
  • Add a squeeze of lime and a sprinkle of coriander leaves.
Ready to be served on a bed of spicy noodles. Just squeeze on some lime and garnish with coriander sprinkles.

Topping for a second time

We’ve learned a lot from the first topping…

Different varieties of chilli like topping in different degrees. Some just don’t seem to understand what to do and others get it right first time.

A good example of a slow learner is Poblano. At the initial topping, Poblano was topped carefully to leave four true leaves. All seemed well. However, each of the plants has grown just one (or maybe two) new branch from the leaf node. This has then become the main growing stem again. It’s like the Auxin only made it down as far as that node and stopped there. Result: minimal branching, one main growing point AGAIN.

Topped Poblano, falling back into its old habits: one growth spike, minimal branching.

The best in class when it comes to branching out has got to be the Chinense group. Again, they were topped to leave four true leaves. This was difficult as they were tightly packed. Every single node has sprouted a new branch. Result: lush, dense plants with plenty of growing branches to bear lots of fruit.

Just look at all those new shoots. The Chinenses may be slow to grow but when they do it is ALL GOOD.

Espelette seems to know what to do with itself once its top has been whipped off. The difference is obvious looking at plants that have and haven’t been topped. Well done Espelette. We salute you.

Left: topped plant with branching at every leaf node. Right: taller plant, no branching, beginning to show a Y at the top. Flower buds.

Overall, topping HAS resulted in the chilli plants growing extra branches, lower down, before they form the Y. It has delayed flower formation and therefore flower drop or fruit developing too soon. Sometimes chillies forget to produce more flowers if they have an early fruit or two.

The Demon Scissor Snipper has been back. A second topping has occurred. Any plant that had not yet formed a Y has had its new branches topped too. Mwwwhhhhhaaaaarrr!

Why? In aid of even bushier plants, with more flowers, less chance of branch snapping and plants that topple over. And of course, many more chillies!

Pinching out, plants, progress and potting on.

The last few weeks have been busy. Spring has finally sprung in Hampshire. The garden is waking up and our Family and other Animals are demanding attention. The chillies have been quietly doing their thing on the window sill. After a sunshine-tastic Easter Bank Holiday it is time for a progress report.

Potting on…

Roots were starting to appear at the bottom of the smaller pots. A sure sign it is time to pot on. Not too big too soon or the plants will spend all their time growing new roots to fill the massive pot and forget to grow up top.

The same mix of soil was used. Seemed to work well for the first round of pots so why change it? No need for staking any plants yet. This time last year the Jalapeños and Big Bombs were already needing a small stake to stop them flopping over. Topping has helped the plant stability.

86 plants potted on. Very satisfying.

As a result of topping…

The plants have responded well to their growing tip being pinched out. Some plants were showing signs of branching anyway but others, less natural spreaders, have really bunched up and sent out side shoots galore. Excellent work. Although none of the topped plants have flower buds they all have many, many more growth points, rather than one leading spike.

A comparison of topped and not topped plants show significant differences (significant to us, anyway) Topping has slowed flower development, created more leaves, bushier and shorter plants. The non-topped plants are destined to be sold at a Summer Fete. They are tall, flowering plants with big leaves. They should do well in their new homes.

The late-to-be-sown Rocoto plants have just been topped. They are rapid growers and have a good number of true leaves. Snip snip snip. Time to bush out.

Last year the solo Rocoto plant we grew was a real pain in the greenhouse. Sprawling and brittle, it decided it needed other plants to support it. This made moving them around almost impossible. It was definitely worth the hassle (as is clear from the last minute seed planting) but there is nothing wrong with attempting to keep them more compact this year.

Rocoto chilli plants freshly topped.

Moving up to the greenhouse…

The plants been up in our heated, bubble wrapped greenhouse for nearly a week and the results are good. All round light, controlled temperature and gentle air flow has really allowed the plants to flourish. We’ve been trying to keep the temperature above 15 degrees at night, so far no problem, despite outdoor temperatures hovering around zero. Temperatures during the day are less than perfect. It can often be well over 35 degrees in there, with window and door open. We’ve attempted some strategic placing of the hotter types on the South side and the ones that are less tolerant of high temperatures on the North side or somewhat under the shelving. Generally all the plants have added a couple of extra sets of leaves and are looking tip top.

There are a selection of plants that will be gifted to friends and family. These are not necessarily going to be potted on or placed in prime location though, just kept ticking along. They will be left in their first pots or potted on into odds and sods pots. A good chance to clear out any unwanted pots. These are in the cold frame, covered over at night and will be fleeced if a cheeky frost makes a surprise appearance.

Potted on ready to sell at the school Summer Fete.

All the Trinidad Perfume plants are showing good growth but have odd looking central new leaves. Pale and crinkly. Investigations and results will follow.

Trinidad Perfume plants showing signs of nutrient deficiency. Time to investigate.

Time to consider the feeding regime again. Should we increase the Chilli Focus mix to 10mls per litre? Should we go to twice a week or stick with once a week? Is an Epsom Salt spray needed again? And what about banana tea?


How and when to top your chilli plants?

Our chilli plants are progressing nicely. Lighting has been au natural so they are not the deep, dark, dense green & glossy beasts that some people have lurking beneath their grow lights. Maybe Father Christmas will bring us lights this year, who knows. Until such time, we have our lovely honest plants that have germinated and grown in a UK Winter. As a result, they have slightly petite leaves, longer stem spaces between pairs of leaves and a grassier green colour.

It is time to top.

What does that mean?

You might call topping, pinching out, top pruning or even FIMming (Google that for an explanation). The Chelsea Chop works on the same idea too. They are all pretty much the same thing. Snipping off the growing shoot at the top of an immature chilli plant, before it has split to a Y or produce flower buds.

You can tell if the plants might benefit from a topping if they are leggy. Look at the space between each set of true leaves. Is it bigger than you would like? Does the plant bend a little too much? Are you worried you might snap the plant when you move it around? If yes to these questions then your plant is ready to take its top off.

Why? What are the benefits:

More fruit: the removal of the main apex growing shoot sends the key plant growth hormone, auxin, down the stem to encourage many more growing shoots to develop further down the plant. The result is more growing branches, more flowers and ultimately more fruit. Yay! Better order that chest freezer now.

More compact plants: naturally grown plants can be a little leggy at this time of the year. This can be dealt with in a few ways. When repotting they can be buried up to their seed leaves, encouraging more roots to grow and reducing the height of the plant. Topping also deals with a plant that is undesirably tall early in the season. Don’t be scared now, it will all work out fine.

More stable plants: another benefit to reducing the height of the plant and sending it out sideways will become apparent later the season. Some chilli plants (jalapeño, guajilo, padron to name a few) could reach up to 2 metres tall. By encouraging a bushy style plant you will avoid plants that can be blown over in the wind, or knocked over if they are dry. Single tall stems can be easily snapped, especially ones that have larger fruit. Multi stems not so much. All that hard work could end up for nothing. You might find there is less need for staking too.

Are there any negative effects?

Delayed flowers and fruit: so of course, by topping the lead growth shoot you are delaying the onset of flowers and fruit, essentially checking the plant. If you have a short growing season and are only interested in a smallish crop then go right ahead, let the chilli plant grow as it wants, with little interference, and you’ll be harvesting your chillies a week or two before us toppers. Although, you might find that those early flowers do not hang around to set fruit as the plant is too immature to support them.

Less side shoots: Hmm, maybe. If you have a chilli plant that likes to bush out and make side shoots all on its own then cutting off some of the plant will leave less leaf joins to sprout new shoots. Don’t top if you have all the space in the world. A side shoot variety (padron for example) will just get on with things itself. As long as you are prepared to stake and support as the fruit sets and enlarges.

Does this work for every type of chilli?

The topping principal totally works on any chilli. But, with naturally small, bushy plants, or plants that send out side shoots you might choose not to bother. Our Chinense types are half the height of the larger Annuums at the moment. No need to do anything with them just yet, maybe not at all. They take a lot longer to get on with things. Bactuum types are often spindly and branched anyway. Topping could help keep them more sturdy.

Top left: Trinidad Perfume (Cap. chinense), bottom left: Aleppo (Cap. annuum)

How to top?

Well now, if you are a You Tube kinda chillihead then settle down to watch Veronica Flores explain all things topping. You’ll be rushing off for your tiny scissors in no time at all.

  1. Wait until the plant has between 3-5 sets of true leaves.
  2. Find a nice sharp pair of scissors.
  3. Take a deep breath.
  4. Snip out the main growing shoot. Leaving one or two pairs of true leaves, depending on how brave you are.
  5. Sit back and watch the side shoots grow.
  6. The side shoots can also be topped later on in the season if they are leggy.

Five days later and our plants are already showing sign of side shoots.

Do be warned: topping is addictive.