Identifying Nutrient Deficiencies in your Garden (Part II)
Hello and welcome to the second instalment of ‘Identifying Nutrient Deficiencies in your Garden’ - aka the section where I actually talk about how to identify nutrient deficiencies in your garden.
If you’ll remember, Part I (which you can read here) got somewhat derailed by a tangential rant about soil pH, which - though ever-so-slightly off topic - really does play a massive role in plant nutrient deficiencies. So I’ve decided that was ultimately a very good thing. BUT if last week’s post left you feeling a little… deficient in your capacity to identify deficiencies - fear not! I’m back to finish the story!
Side note: you know when you learn a new word and then suddenly everyone seems to be saying it all the time? Turns out the same thing happens with nutrient deficiencies and now I can’t bloody drive down the highway without diagnosing the root cause of all sickly plants! Which is fun but also distracting. If you are prepared to suffer this same obsessive fate, read on.
Yellowing older leaves with green veins are characteristic of a magnesium deficient plant
Signs of a nutrient deficient plant:
Ok, so. Let me begin by saying that quite unhelpfully a lot of different nutrient deficiencies cause very similar symptoms in plants. Typically, some kind of yellowing or discolouration of their leaves. This makes diagnosing the deficiency a bit tricky, but don’t worry! I’ve created a Pinterest board containing images of plants with various nutrient deficiencies, plus a heap of handy infographics to help you work out what’s ailing your garden buddies.
Mobile and immobile nutrients:
One thing to bear in mind when trying to work out the cause of your plant’s nutrient deficiency is whether the discolouration is affecting old or young leaves. This will often give you clues about what nutrient may be deficient.
Certain nutrients (nitrogen, phosphorus, potassium, magnesium and chlorine) are classed as ‘mobile nutrients’ which means that the plant is able to move them around, sending them to the areas that need them most. This means a plant that is just becoming nutrient deficient will preferentially shuffle these nutrients from its older leaves towards its younger leaves (which need them the most). As a result, the signs of mobile nutrient deficiencies appear on the older leaves first.
On the other hand, some nutrients (boron, calcium, copper, iron, manganese, sulfur and zinc) are immobile nutrients, meaning once they’ve been incorporated by the plant they cannot be shuffled around inside the it. This means even if the older leaves contain adequate amounts of the nutrient, once the plant becomes deficient the nutrients cannot be moved into the younger leaves. As a result, the signs of immobile nutrient deficiencies appear on the younger leaves first.
And now, here’s a brief rundown of the more common nutrient deficiencies, their trademark symptoms and how to address them:
Bleached or yellowing young leaves with green veins are characteristic of an iron deficient plant
Nutrient deficiencies up close
Primary macronutrient deficiencies:
Nitrogen deficiency: Old leaves turn from a dark green to pale green and then progressively turn yellow. This starts with the older leaves and then progresses through to younger leaves. Usually the entire leaf (including the veins) turn pale green or yellow (see photos here). The solution: add a good quality animal fertiliser to your soil.
Phosphorous deficiency: Old leaves turn a darker green followed by a purplish tint that starts around the edges of the leaf. Leaf tips may turn brown (see photos here). The solution: add a good quality animal fertiliser and/or sprinkle some blood and bone on top of your soil.
Potassium deficiency: Old leaves turn pale and yellow, beginning at the edges. The plant does not wilt, but older leaves may develop dead brown spots, or the entire leaf may turn brown and die (see photos here). The solution: add a good quality animal fertiliser, a high potassium fertiliser (e.g., sulphate of potash or tomato feed), wood ash (in small amounts) or banana peels to your soil. Note: generally I think it’s better to add animal manure rather than liquid/powder fertilisers, as manure improves the structure of the soil as well as adding nutrients.
A happy hyacinth. Because we can’t ONLY stare at photos of deficient plants.
Secondary macronutrient deficiencies:
Calcium deficiency: Young leaves are small and misshapen; they may become crinkled or torn and develop dark veins or brown spots (see photos here). In tomatoes, calcium deficiency can lead to blossom end rot. The solution: Calcium deficiency is often associated with overly acid soils, so check your pH to rule out soil acidity. Add organic matter to the soil to improve moisture retention. You can also return calcium directly into the soil by adding gypsum or bone meal.
Magnesium deficiency: Old leaves turn pale or yellow between veins while veins themselves remain green. Brown spots may develop between veins (see photos here). The solution: Add Dolomite to the soil (about 1 handful per square metre) once a year in autumn. In tropical climates where the soil receives a lot of rain, add Epsom salts diluted in water and spray directly on the plant’s leaves about once a month. Note: magnesium deficiency looks similar to iron deficiency except magnesium deficiencies affect old leaves while iron deficiencies affect young leaves.
Sulfur deficiency: Young leaves turn from a dark green to pale green and then progressively turn yellow. This starts with the younger leaves and then progresses through to older leaves until the entire plant has yellowed. On each leaf the veins also turn pale green or yellow - in some cases the veins may be even paler than the rest of the leaf tissue. Sulfur deficiency can look very similar to nitrogen deficiency, so pay attention to which leaves are affected first. If old leaves are affected first, it is likely a nitrogen deficiency. If young leaves are affected first, it is likely a sulfur deficiency (see photos here). The solution: Add a good quality animal manure, gypsum, ammonium sulfate or elemental sulfur.
Micronutrient deficiencies:
Boron deficiency: Young leaves (as well as the roots or fruits of affected plants) may appear deformed or stunted. Tips of leaves can become brittle and yellow (see photos here). The solution: A small amount of boric acid can be diluted in water and sprayed onto the leaves of the plant. However, excess boron is toxic to plants so it’s important to be sure that boron deficiency is really the problem before adding additional boron. Boron also becomes less available in alkaline soils, so check your soil pH as well.
Chlorine deficiency: Older leaves start to develop small, white necrotic spots along their edges. Unlike spots caused from other leaf diseases, spots caused by chlorine deficiency tend to have distinct, abrupt boundaries between the damaged parts of leaf tissue and healthy leaf tissue. The tips of the plant’s leaves may also curl or wilt (see photos here). The solution: Add a good quality organic fertiliser or a chlorine containing fertiliser such as muriate of potash (potassium chloride or KCl).
Copper deficiency: Young leaves turn pale green or yellow and may become deformed or curled. Initially, the veins may remain green, but can turn pale green or yellow in the case of a prolonged copper deficiency. Leaves can also develop brown spots and wilt (see photos here). The solution: add a good quality organic fertiliser or animal manure.
Iron deficiency: Young leaves turn pale green, yellow or (in extreme cases) white between veins while veins themselves remain green (see photos here). (Note: iron deficiency looks similar to magnesium deficiency except iron deficiencies affect young leaves while magnesium deficiencies affect old leaves). The solution: Iron is typically abundant in most soils, so usually you don’t need to add more iron, rather, you need to fix whatever is preventing your plants from absorbing the iron. Improve soil structure by adding organic material into the soil (e.g., a good quality compost), if your soil is very wet or compacted add grit, and avoid using high phosphorous fertilisers (which can impede iron availability).
Manganese deficiency: Young leaves turn yellow while their veins remain green. Looks a lot like iron and magnesium deficiencies. Unlike magnesium deficiencies, however, manganese deficiencies appear on young leaves (making them harder to distinguish from iron deficiencies). To distinguish manganese deficiency from iron deficiency look out for burned brown spots on the outer edges of leaves. These changes become more severe as the manganese deficiency progresses (see photos here), while plants that are iron deficient turn progressively white. The solution: manganese deficiency is often associated with poorly draining soils, so improve your soil structure by adding grit and organic matter. Also test your soil pH as manganese can become unavailable when soil pH is high.
Zinc deficiency: Young leaves show stunted or deformed growth and turn a pale green or yellow colour. Leaves may develop brown necrotic spots or turn a bronze colour (see photos here). The solution: add a good quality organic fertiliser or animal manure and check your soil pH as zinc may not be available in highly alkaline soils.
A few other thoughts…
Well blimey. Aren’t there a WHOLE lot of ways plants can get malnourished?! Who knew! At this point, let me tell you what I intend to do in the future.
Preeeeeetty much nothing. Apart from what I’ve already been doing for the last six years, which is: feeding my plants a steady diet of lupin mulch and animal manure and thinking mostly about nice things like butterflies, sunflowers and ladybird larvae. At the end of the day near enough is totally good enough. Your plants will be fine, just make sure you do the most important job of actually enjoying your garden.
I’m also going to attempt not to worry too much about my alkaline soil, and instead of trying to change the pH with any whacky amendments, I’m going to continue focusing on creating a really healthy topsoil layer that covers my entire garden, using a combination of lupin mulch, animal manure and homemade compost.
(Maaaaybe I’ll scatter a tiny bit of sulfur around the citrus trees…just to see what happens).
Good to keep things (relatively) simple.
(Incidentally if you’re considering adding rock dust to your soil - which I was - have a read of this article discussing whether or not the whole ‘rock dust’ thing is a giant myth. I’m starting to think it might be worth saving the dolla$ and spending them on a whole heap of cow dung instead - now that’s what I call no bullshit bull shit)
And lastly…
…let it be known that I usually like to imagine you all reading these blog posts somewhere comfortable and sunny, with a hot cup of tea beside you and some kind of pleasantly chilled out saxophone playing in the background. So I try to write posts that compliment that overall …vibe.
Needless to say a comprehensive ~ DEEP DIVE ~ into leaf deformities and nutrient deficiencies does not seem entirely fitting with that peaceful, sunshiney picture. But I have to admit, forcing myself to trudge through the quagmire of internet agriculture websites to distill the relevant information has proven highly educational!
So even if this was not the most emotive, jolly, lyrical or romantic read, I do hope it will prove repeatedly useful for you and your plants over the next days, months, years, lifetimes! Next time a plant is looking at you funny, race back to your computer, get your befuddled butt back to this blog and work out, once and for all, exactly what ails it!
(Unless, you know, it’s got one of the other bazillion fungal infections, mite infestations and general plant plagues that ravage the planet. In which case I guess today is just not your day)
Sigh. It’s a tough job being a gardener. Lucky it’s so bloody pleasant! :D
