Lemandarangequatelo,

Sorry to hear about the damage to your trees. Just wondering if there is anywhere in your house that you could overwinter them?

Also, it might be an idea to take cuttings from each of your trees and propagate them just in case the worst case scenario happens.

We had -6C here two night ago and I had the fan heater on in the conservatory the whole night. Thankfully, the weather has improved now.

All the best,

Simi

Hi Simi, thanks for replying and for the good wishes. I wish I could propagate them from cuttings, but I've had zero success with citrus cuttings in the past, they are so hard to root. My greenhouse is getting heat again so hopefully no more problems till winter is over. I hope your citrus are doing good.

Hi Darkman, thanks very much for your reply and advice, I found it very helpful. I'll do as you suggested and I won't use the 5-5-5. I'll look for the individual components instead, thanks for the tips!

Thanks again Darkman, I will bear that in mind.

I cannot offer with any certainty the best ratio of NPK to apply to an ailing citrus. The 1-1-1 (such as a 5-5-5) with an additional micro-nutrient boost is what I've used and here was my reasoning: The goal we're hoping for is increased root development, which (over-simplified) comes from the P component. But plants rarely absorb more P than K (so a 1-3-1 isn't any better than a 1-1-1). Since it's normally recommended that healthy growing Citrus get N in (almost) a 2:1 ratio as K, then cutting the N in half for this situation would be 1:1 ratio. Given the P to K limit above, a 1-1-1 made sense.

Or explained another way, using a balanced 1-1-1 fert with micros is a basic way to apply nutrients to container trees. You would most likely hit a N deficiency first for a healthy Citrus in full growth, but a reduction in N is exactly what we're looking for.

But I'm always open to learning why a 1-1-1 with micro boost wouldn't be appropriate.

The idea of applying individual NPK components is good, but I'd be hesitant to recommend it to someone without experience -- or unless someone with the experience gives them the exact individual products to buy and the ratio to apply them. While generally being safe individually, mixing different products can cause excess of specific micro-nutrients of which some are hard to correct (i.e. balance or leach them out).

I would be careful about using individual organic ingredients unless you know exactly what it is you are using and the consequences of using it. For example, applying a good/correct qty of wood ash (also for K, Potash) can problematic for drainage by clogging up the macro pores in a good mix. You'd need to be aware of the time it takes for plant absorption before inadvertently applying more via another method.

You are still definitely in the wait-and-see phase so I wouldn't buy much of anything yet.

Organic fertilizing is one method of growing citrus, and organic growers use various organic ingredients to supply nutrition to their trees. In my personal opinion, for container citrus, or for that matter in ground citrus, I personally would never use this method. When I say this, I usually hear form an organic grower or two. However, citrus are heavy feeders, and therefore require a lot of nutrition to preform at their best. Research has found that citrus absorb nutrients in the NPK ratio of 5-1-3. Meaning that for every 5 parts N, the tree absorbs 1 part P and 3 parts K. You being in the UK, I doubt very strongly if you will be able to locate a fertilizer with this ratio. Try to find one as close as possible. What ever fertilizer you use be sure it also contains all the trace minerals. Actually, citrus trees growing in the ground, are not all that finicky about the fertilizer formulation used. This is because fertilizer applied over the soil is absorbed by the tree and and is also flushed away with each watering or rain, but like all citrus tees, in ground citrus still absorb nutrients in a 5-1-3 ratio. For trees growing in enclosed container this ratio becomes quite important. Fertilizers must be chosen according to the replacing the minerals absorbed and their ratio. - Millet (770-)

Hi C4F, thanks very much for your detailed advice. Wow, this is getting complex now, you can tell I'm a newbie lol, but it's great to learn. I certainly wasn't rejecting your earlier advice, it made sense, I just couldn't find a 1-1-1 fert. As you said Darkman's advice was also good, but also you are right that an inexperienced grower such as myself would have trouble finding and using individual NPK components.

Darkman I'm certainly not rejecting your advice either, it was good but I realise now I'm just too inexperienced to implement it. Upon further investigation I just can't seem to find products with individual NPK components that are easy and straightforward to use. I found some root and bloom stimulators but they never give their NPK ratios.

Millet, thanks very much for your input. You're right I can't find a 5-1-3 fert here in the UK. The closest I can find is 28%-7%-14% which if I calculated correctly would be 4-1-2 ratio fert, and it says it contains all the trace minerals too. This is what I usually use and it seems to work ok for most of my citrus plants.

I thank everyone for their input and advice so far, I really appreciate it. I think I will wait and see with my trees and seedlings. They are all looking pretty sorry at the moment. No leaf drop yet, but all the leaves are still drooping and looking to turn brown or pale, and on some trees look really brown and dead. On one tree there is drying out of the very top leaves. Fingers crossed they will all survive. The greenhouse is heated again but not to a high temp, just to keep everything above freezing.

If N is wit held, or worse depleted, the tree will die. - Millet (769-)

Darkman,

I'm being lazy atm to lookup my research material but you are correct there are relationships between the NPK and also between the macro and micros as far as uptake problems. Which is why I was offering safe advice of just going with a simple 1-1-1 that is available at big box stores and then buying a micro-nutrient "boost" which you can get at most nurseries.

Stan,

If you really want to simplify everything and have some peace of mind for your citrus AND if you are used fertilizing with a soluble solution (like Miracle grow or Miracid drops), a great product is DynaGro Foliage Pro. It is about 6 yrs old (fairly new on the market) but is finally showing up in my local Hydroponic stores. DynaGro has many other products that are on the shelves, but the Foliage Pro product is a 3-1-2 ratio that has all the micros you'd need for citrus, including Magnesium and Calcium (two of which can be finicky if not given in balance). If you only used this product by the label directions, your tree would very likely never suffer from nutrient issues caused by over, under or imbalance fert applications. To date I have yet to see a product that contains all the micros needed, almost all are missing Ca and Mg (and for citrus, Ca is definitely needed).

If you currently fertilize only a few times a year by throwing the pellets (a.k.a. granular feeding) then switching to soluble is probably too much work for you (it was for me). Ideally, you'd apply it at every watering during peak growing season, but twice a month normally and a small dose once a month during winter.

It's moderately priced for a small bottle, but it lasts a long time since you only use 1/4tsp per 1 gallon during most months of the year. It's only $13 for 8oz via Amazon free shipping, which makes almost 200 gallons at maintenance ratio (every watering) equivalent to at least 400 feedings for a typical sized container citrus tree.