ms-minnamouse,
I don't know what you are growing to need all that. I have a mix of lawn grass, oak leaves composted and use 2 parts with 1 part peat moss and 1 part mushroom compost and add a little 10-10-10 guano what ever I think my plant will need to grow good and produce. I have a beautiful self watering bucket garden now useing the mix that I had for last summers garden, I just mixed more 10-10-10 into the top half of the bucket and planted.

DAN

I also forgot, there's no way my mom would want guano in the house.

And also, that's a BUNCH more stuff than just three items that I use.

There are some unwanted repercussions that could occur if you were to simply add Epsom salts to the fertilizer water. Mg and Ca are antagonistic elements, which means that too much of one can affect the uptake of another. Generally, the Mg component in container soils is furnished when the soil is made, when dolomitic lime, CaMg(CO3size>)2size>, is added to buffer the pH upward into the 6-6.5 range. This material supplies both Ca and Mg, and it supplies it in roughly a 4:1, Ca:Mg ratio. When this ratio gets too far out of balance, as in when we add either Ca or Mg w/o adding the other in a favorable ratio, an antagonistic deficiency of one element, and even a toxicity of the other can occur.

Generally, if your plants are exhibiting a Mg deficiency, a Ca deficiency will soon follow (after all, they are both supplied in the dolomitic lime). If you can, it is better to try to supplement Mg with dolomitic lime, which will keep the ratio in balance & supply the Ca which is likely to be in short supply as well.

If by chance, you or the soil packager used gypsum as a Ca source, CaSO4size>, it would be appropriate to supplement Mg by adding Epsom salts to the fertilizer water (if the fertilizer doesn't contain it) at the rate of approx 1/8 tsp/gallon.

Side note: Many granular/soluble or liquid fertilizers contain no Ca or Mg for several reasons, so read your fertilizer labels.

Al

Forgot to answer your Fe chelate question - sorry. ;o)

Fe and Zn become increasingly unavailable in soils as the pH rises. To compensate for the unavailability, we take advantage of chelates or chelation, which is simply the bonding of these elements to organic molecules, which increases their solubility and thus, availability. No one can really answer whether you need them or not, w/o knowing something about your soil solution pH and existing Fe levels. I know that my water pH runs high, especially in the summer, so I compensate for the inevitable pH induced Fe deficiency by using "Sprint 138" an Fe chelate especially formulated for high pH applications. I suspect that if you have a known high pH in your water supply, that the chelate applied within suggested guidelines would likely be appropriate. If your water is near neutral or on the acidic side, it's probably not needed.

If you're only talking about a few plants, often the Fe & Zn is present in ample amounts in the soil, but is unavailable because of the pH issues noted above. If this is the case, acidifying the irrigation water with a Tbsp. or two of vinegar/gallon is often enough to correct the deficiency.

Al

Q: How much and how often should I use Epsom salt... chelated iron and zinc?

What are you growing and in what root medium with respect to your questions? Is your plant exhibiting symptoms and what are they?

The more information and history you can provide about your plant and your gardening practices, the more precise we can troubleshoot and offer relevant options.

There are technical papers refuting and disputing an ideal Ca:Mg ratio exists or should be used as a reliable parameter in fertilizing and maintaining productive plants.

Just in general. I grow many different, varied things and use different brands of potting soil all the time. And sometimes it's for plants in the ground.

I really don't know what the pH is here, I keep forgetting to check it.

I forgot to say that epsom salts have helped in the past with tropical hibiscuses in both the ground and potted, when they were yellowing.

For general use of Epsom Salts and chelated iron and zinc, I would always follow manufacturers instructions and recommendations.

For hibiscus, I would maintain the root medium slightly acidic at pH of 6.5-6.8 to help the hibiscus absorb nutrients. I would fertilize differently and less in dilution and/or frequency as recommended on the label for indoor hisbiscus than outdoor ones. Fertilize more during the growing season only (March-October for hibiscus I believe) to help keep hibiscus blooming and looking their best.

Iron and zinc are minors so most plants including hibiscus shouldnÂt need much or duplicated supplementation and/or on a regular basis. However, keep doing what you are doing on duplicating the supplementation of iron and zinc if your hibiscus does not show symptoms of nutrient disorders (either deficiencies and toxicities) and/or should there be identifiable signs of iron and zinc deficiencies. ItÂs also possible that with your regular iron supplementation, especially in containers, the root medium isnÂt deficient in iron but instead is alkaline (high pH), which makes less iron sufficiently accessible to hibiscus. In which case (confirmed by a high pH test of your root medium), you could also lower the pH of your root medium/soil by amending it with agricultural sulfur (fine grade for pots) instead of wasting money by adding more unavailable Fe and create more potential problems. Your plants are your best guides in letting you know if you are ultimately meeting and providing all the cultural and nutrient requirements qualitatively and quantitatively. Experiment and see what works well for your local growing conditions. Due to changing seasonal conditions, stages and cycles of maturation, and water quality, it makes sense to maintain and adjust your fertilizer regimen accordingly by observing the changes exhibited by your plants in addition to a set fertilizer formula, regimen, and schedule. The same principle would apply with your skin care, exercise regimen, or diet. Similarly, you will need to observe symptoms and undesirable/unusual changes in context of changes in your root medium pH, relevant environmental changes, and your horticultural practices in order to diagnose possible nutritional disorders to take proper and relevant corrective action.

Depending on the growing conditions and types of root medium of your hibiscus, it appears that hibiscus may have a special need for supplemental magnesium as suggested by some hibiscus specialists. I would follow the application instructions recommended by your Epsom salts manufacturer. And if you still see magnesium deficiency on your hibiscus, then use either more of it or more regularly. Use diluted amount and more regularly is the safer way for a plant and more user friendly for a gardener.

Hope this is helpful.

Ahhh, Ms M - you didn't mention you were talking about hibiscus! ;o)

This is one of the few plants that generally prefers a little more Potassium (K) than Nitrogen (N), but something more more important - and what many people are unaware of, is that hibiscus neither need, nor want, high amounts of Phosphorus (P, the middle number in the fertilizer blend), so NEVER use a "bloom boosting" fertilizer on hibiscus. The best choices of tropical hibiscus fertilizers will have ratio numbers similar to 9-3-13, 10-4-12, or 12-4-18.

I have found that I can take a slightly different approach in fertilizing the plants I care for by adding a rounded Tbsp. of potash per gallon of soil when I pot the plants in spring. This adds the extra K the plant craves and allows me to use the easy to find 12-4-8 MG liquid fertilizer that I use on almost all my plantings. BTW - I do also recognize the plants preference for added Mg and I usually always add about 1/8 tsp per gallon of Epsom salts in my fertilizer water. I fertilize these hungry plants very often (weekly at least, if the soil is fast-draining) at about 1/2 recommended strength.

To recognize a Mg deficiency in tropical hibiscus, look for older leaves to turn bronze yellow with green persisting at their tips and lower central vein areas. The plant is slow to react to Mg deficiency correction if you add it to the soil, so if you suspect a Mg deficiency in hibiscus, the best and fastest way to alleviate it is to prepare a foliar spray of 1 tbsp of Epsom salts dissolved in a gallon of water & spray leaf & branch surfaces.

Take care.

Al

Just want to make sure it was clear to you that you would only need to pH down to the stated ideal pH range by adding agricultural sulfur to increase iron uptake by the hibiscus if you see BOTH iron chlorosis (yellowing with thin green veins, interveinal chlorosis, of upper new leaves) on your hibiscus AND the pH of the root medium pH is also greater than the ideal pH suggested above in the presence of your regular supplementation of iron and zinc. On the other hand, if there are existing signs of iron chlorosis, a little added sulfur will not be too detrimental to your hibiscus in altering the pH too much even without a soil pH test (but may reduce the availability of Mg) as long as you use less or follow the recommended use, but have a soil pH test done before and after amending with sulfur will give you added confirmation, assurance, and relevant feedback that ideal conditions are supplied for your hibiscus or the plant in question.

In several plant species and due to the extent and length of time of a nutrient deficiency and possibly several related defiencies (or toxicities), symptoms of iron chlorosis and magnesium deficiency (as well as manganese deficiency) can be indistinguishable. Broadly speaking but with variables and conditions indicated above and because Fe is classified as a non-mobile nutrient, any iron chlorosis (deficiency) would affect the upper young leaves first whereas magnesium deficiency would be identified by the affected older and lower leaves first because magnesium is classified to be a mobile element in plants and soil. My approach would be to "engine search" images (Google Image) of iron and magnesium deficiencies FOR hibiscus and the cultivar you are growing if possible for identification if you suspect iron and magnesium deficiencies that make sense in context of your watering and fertilization practices and any measurable conditions of a root medium. Preventative and light use of epsom salts will generally keep plants and grass green and likely to be harmless because of the added sulfur and magnesium. However, to me and I prefer that all or most of the puzzle pieces and clues have to fit together before I make a diagnosis to determine a probable cause somewhat systematically and accurately to take major corrective actions because any changes affecting the balance and availability of one element will often affect the availability of other associated elements in soil chemistry.

But then again and speaking in general terms for your outdoor and indoor gardening needs as you were asking, much of these problems with first, secondary, and trace elements can be somewhat self-regulating if you incorporate sufficient inorganic and organic amendments such as greensand and compost instead of relying mostly on soluble and leachable chemical fertilizers and as witnessed and shared by Dan above and demonstrated in many greenhouse comparison soilless trials. It's true you lose some control and there are some risks of crop losses when a learning curve is involved gardening with clean finished compost in soilless containers, grow boxes, and soil-based gardens (even the hydroponic and semi-hydroponic crowds are doing it), but you may also discover what you were unable to duplicate or like what you see by gardening with less effort, monetary output, and more pleasure. In case you are not aware, gardening with compost is also soilless gardening.

p.s. The NPK ratio of your Miracle Grow (w/ low phosphorus) looks like a good fit to me for your hibiscus.