Fertilser Reccomendations for Adenium Obesum

Hi there.

I noticed on some of the leaves on my desert rose that there's a slight yellow discolouration. It's very limited but still there. I think that it's because it's only been watered and not fed with anything. If I'm wrong what else could it be? But if it is that could you recommend a fertiliser I can use for it?

Thanks for your help.

This message was edited Aug 21, 2011 9:55 AM

Can you post a picture? The other common thing that can cause yellowing leaves is overwatering...Adeniums don't need a ton of water so it wouldn't be hard to overwater it. Things like insect damage can also cause yellowing. I have an Adenium that I hardly ever fertilize and its leaves are fine, so while it wouldn't hurt to give it a balanced fertilizer every now and then, there's a good chance it's something else that's causing the yellowing.

Thanks for the reply. Perhaps it could be overwater. What kind of insects could damage the plant? I wouldn't have thought that it was insect damage, but only because i've never seen insects on it. I'll try and post a picture up of it soon.

It sounds like you need to start eliminating some of the possible causes so you can narrow down the list and concentrate on what's PROBABLE.

Insects, under-fertilizing, over-watering/a poor soil, and a high media or media solution pH constitute the short list of most likely suspects, based on the limited info we have to go on. Containerized plants DO need fertilizer, and WE need to shoulder the burden of ensuring they get all the nutrients essential for normal growth, and not depend on the soil to provide the plant's nutrition. If you ARE depending on the soil to supply the plants nutritional needs, I can guarantee that you're leaving a considerable amount of potential growth/vitality lying on the table.

Since we KNOW you need to address nutrition, regardless of what other issues might be in play, let me say there is little variation in the RATIO of nutrients used across the board by plants, even though some plants use more nutrients than others. Here (below) is a range of relative (to nitrogen) nutrient usage that covers nearly all plants. I gave Nitrogen, because it's the largest nutrient component, the value of 100. Other nutrients are listed as a weight percentage of N.

N 100
P 13-19 (16) 1/6
K 45-80 (62) 3/5
S 6-9 (8) 1/12
Mg 5-15 (10) 1/10
Ca 5-15 (10) 1/10
Fe 0.7
Mn 0.4
B(oron) 0.2
Zn 0.06
Cu 0.03
Cl 0.03
Mo(lybdenum) 0.003

To read this chart, compare (for example) the P usage to N usage. On average, plants use 13-19 parts of P for every 100 parts of N (an actual average of about 16 parts per 100 or about 1/6 the amount of P as N. You can run down the list and see that plants don't use the same amounts of the various nutrients, so it doesn't make good sense to supply them equally, because it ENSIRES either excess or deficiency - it can't be any other way, and an excess can be as limiting as a deficiency.

In the end, after the calculations are made for how P and K are reported in fertilizers, the commonly found NPK RATIO that is pretty much dead on in its ability to provide nutrition in the ratio used by most plants is 3:1:2. RATIO is different than NPK %s. 24-8-16 and 12-4-8 are very common NPK %s that supply nutrients in a 3:1:2 RATIO. I suspect that you probably have something there that is available in a 3:1:2 ratio; perhaps it's even packaged as an 'All-Purpose' fertilizer as it is here in the US. I prefer, for several reasons, Foliage-Pro 9-3-6 soluble fertilizer, another very good 3:1:2 ratio fertilizer that contains ALL the essential elements in a favorable and well-considered ratio.

I grow DRs in a very coarse soil and water/fertilize abundantly while they are actively growing, and they grow extremely well. DRs don't use less water than most other succulents, they just don't tolerate wet feet as well as some other plants. Providing a very well-aerated soil to minimize excess water retention, and fertilizing plants you want to increase the mass of at full recommended strength every week or two while the weather is warm, should find you producing fast growing and healthy plants.

Al

Thank you very much for both your replies, they are extremly informative and have really helped a complete novice (me). I managed to take a few pictures, unfortunately at the moment, I can't take anything better. Today I noticed the tips of a few of the leaves with yellowness are dieing, it's become a greyish colour and appears that the tips are dead. I'll try and get more detailed pictures sent soon! But these will have to suffice for the time being, I hope they're clear enough to extrapolate some useful information.

another pic....

and one more for now...
Thank you for your help

Are you using a fast draining soil? They don't like their roots to stay wet for long periods. Regular potting soil has alot of peat for water retention, you need to use a cactus mix or something that has fast draining soil. Acts

The soil i used was a catus/succulent mix. It came ready made.

as to whether it's fast draining enough, i don't know

Here is a picture of what 'fast draining' looks like. 'Fast draining' may not be enough unless it's also well-aerated. Fine sand might be considered a fast draining medium, but it's wholly inappropriate as a primary fraction of a medium for most plants - especially those like Adenium and other succulents, because of its excess water retention and the ht of the perched water table/column it supports. This becomes even MORE important in shallower containers, where excellent drainage/aeration approaches the critical point.

You might wish to bare root the plant, inspect the roots, remove any decaying tissue so that only sound and viable tissue goes back in the pot, and repot into a suitable soil. WHAT the soil is made of or what the package it comes in says it's good for are far less important than how the soil is structured.

For more info on soils: http://davesgarden.com/community/forums/t/1073399/

Al

I forgot to mention that if you find root rot, you might wish to consider a dip in a 10% solution of unscented household bleach, or a dip in a 10% solution of 3% hydrogen peroxide. Alternately, a dusting with powdered sulfur would be very helpful if you discover a case of the fungaluglies.

Al

Notice how well these succulents are doing in the less than 2" deep collection saucer. That is very difficult to do in/with a soil that supports any significant volume of perched water, but easy when using a highly aerated and fast draining soil.