General garden fertilizer question

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Title: Guest
Joined: 2010-03-01
General garden fertilizer question

A spring bulb catalog suggests fall fertilizer for Narcissus-- as well as 2 spring applications.
I never thought about fertilizing spring blooming bulbs in the fall, but would like to have them as vigorous as possible.
Is there evedence that fall fertilizer is beneficial, and for what plants?
Thanks for any thoughts.
Charles Swanson Massachusetts USA

Hoy's picture
Title: Member
Joined: 2009-12-15

As  many bulbous plants do grow a lot of roots in fall I would say it is a sound advice. But it has to be done before the soil gets too cold. And anyway before the soil freezes solid!
I don't fertilize in fall though.

Rogaland, Norway - with cool, often rainy summers  (29C max) and mild, often rainy winters (180 cm/year)!

Title: Moderator
Joined: 2009-09-21

the Daffodil Society is a little ambiguous on this, if you ask me.

It says in #3 to amend the soil with compost or the like in the fall before planting, and does not mention fertilizer per se.
But in #5 it says to top dress again (?) with 5-10-10 at leaf tip emergence and another time with 0-10-10 as they flower.

So maybe just a little fertilizer in the fall?

I have some hybrid daffs from the previous owner of my house that grow in crappy brown clay.  I never fertilize them, and the clump has double in size in 10 years.

Rick Rodich    zone 4a.    Annual precipitation ~24 inches
near Minneapolis, Minnesota, USA

Gene Mirro
Title: Guest
Joined: 2010-02-25

If you fertilize in Fall, a lot of nutrients are going to leach away over the Winter and early Spring, at least in my rainy winters.  The plants are not very active in Winter, because of the low soil temps.  I wait until Spring to fertilize and lime.  The rain washes the nutrients down to the root zone pretty quickly, and the plants are actively growing, so it seems to work well.  Phosphorus and Calcium are not very mobile in the soil, but they do eventually make their way down to the root zone.  Also, they are not easily lost by leaching, again because they are immobile.  So you only need to apply Phosphorus and Calcium once every year or two.  Also, you don't want to overdo the Calcium, because it will make your soil alkaline.  Although in Massachusetts, I doubt that you need to worry about that.  Ideally, your soil pH should be in the 6 - 6.5 range.  

Nitrogen and Potassium are very mobile, so a Fall application is likely to be leached away before the plant can use it.  

Experience is the best teacher.  I get very good results with Spring fertilizing, just as the foliage emerges.  For Dutch bulbs, I apply dolomite lime (Calcium and Magnesium), bone meal (phosphorus), and a little NPK commercial fertilizer (but don't give bulbs too much N).  I also apply a little Micromax trace element mix once every couple of years.  

As far as soil preparation, I find that the best soil for nearly all bulbs is sandy loam.  I always seem to end up with clay loam, so I spend a lot of time adding sand to the soil.  I know you're not supposed to add sand to clay, but if you read a little, you'll find that people have been doing it for at least 1,000 years.  I've been improving heavy soil with sand all of my life, and it has always been successful.  If you've got heavy soil, add about an inch of coarse sand and till it in thoroughly about 6 - 7 inches deep.  My soil requires about 2 inches of sand.  I buy sand by the dump truck load.  This is really heavy work, and it helps to rent a little tractor with a bucket and tiller on it.  You will not believe the improvement in plant growth once you've got sandy loam soil.  All sorts of mysterious problems just disappear.  BUT:  if you've got impenetrable subsoil clay, like the kind that developers like to leave around new subdivisions, forget about the sand.  You will need to purchase topsoil and put it on top of the clay, or replace some of the clay with topsoil.  And you must fix drainage problems, which are death to most bulbs.    

Another thing that works well is raking your soil into raised beds.  You can almost double the effective topsoil depth that way, and greatly improve drainage and aeration.  And it is easier to weed.  Also, it never hurts to till some organic matter into your soil, and/or mulch with organic matter.

Once you've lightened your soil, and adjusted the acidity by adding lime, and started applying fertilizer annually, you will find that most bulbs will thrive and multiply rapidly.  You'll be giving them away.  This assumes you are growing them in full sun, which most bulbs need. With partial day sun, the plants will be less vigorous, and will not bloom every year.  In extreme cases, you will get leaves only.

If you grow bulbs under trees, they will be shaded, and the trees will grab all the fertilizer once they break dormancy in late Spring.  So feed the bulbs early, while the trees are dormant.  

SW Washington state, 600 ft. altitude

deesen's picture
Title: Guest
Joined: 2011-01-31

The bed I use in the garden for Daffs gets top dressed each year in mid-late Summer with potting mix from the re-potted bulbs I grow under glass (a good gritty/sandy mix). This usually provides me with a little crop of miscellaneous bulbous seedlings that I've missed collecting too. I usually give the bed a sprinkling of bone meal at the same time. As the bulbs are just beginning to go over they get a feed of sulphate of potash applied in powder form and watered in, in the unlikely event of it being dry here! If dry too during the growing season they get a half strength dose of tomato fertiliser.

David Nicholson
in Devon, UK  Zone 9b

Title: Moderator
Joined: 2009-09-21

I've never believed the myth that clay + sand = cement.  Yes, wet clay mixed with sand gives "cement".  Wet clay mixed with anything (even more wet clay) will yield "cement".  And herein originates the myth: people not understanding that soil structure is more important than soil composition.  Not realizing that wet clay should never be worked with, novice gardeners try to "dry" it by mixing in sand.  Wrong!  In the process, they have worked all the tiny air pockets out of the clay, destroyed the soil structure and have in effect, produced cement.
Gene, I'm not sure why you purposely wait until spring to add lime.  If the calcium is relatively immobile in the soil, and the purpose is to raise pH, would in not be better for it to do its job through the fall and winter, ready to go in spring?  Later, you mention you use dolomitic lime.  Is the purpose, then, to add magnesium?

Rick Rodich    zone 4a.    Annual precipitation ~24 inches
near Minneapolis, Minnesota, USA

Gene Mirro
Title: Guest
Joined: 2010-02-25

Yes, the dolomite lime adds both Calcium and Magnesium.  About the Spring liming: we get an amazing amount of rain from late Fall through early Spring here.  So I don't apply any nutrients in the Fall.  Also, I find that plants respond pretty quickly to lime when it is applied in Spring, especially in sandy soil.  So I apply everything in Spring.  Wood ashes are good fertilizer for bulbs, but if you apply them in Fall, everything leaches away.  When I lived on the East coast, I applied lime in Fall, since the ground is frozen all Winter, and there is very little leaching.

One problem with applying everything in Spring is that Ammonia in NPK fertilizer will react with lime, and be lost as Ammonia gas.  So I apply lime first, and wait a couple of weeks before applying NPK fertilizer.  I'm not too worried about it anyway, since bulbs usually don't like too much Nitrogen.

Anyway, once you've gardened in an area for a while, the immobile nutrients accumulate, and you don't need to apply more every year.  Organic matter is great for binding to nutrients and keeping them from washing away.

In lawns or pastures, the leaching problem isn't as bad, because the plants absorb the nutrients before they wash away.  But in a clean-cultivated garden, that doesn't work, because there isn't enough plant cover.

The sand/clay cement theory may come from certain types of clay (which I've never encountered) that don't mix well with sand.  For example, pure clay (which I call subsoil clay) is almost impossible to improve with sand or anything else.  This is why I very carefully state that I am amending clay loam, not clay.  If your native soil will grow a good crop of weeds, you should be able to amend it with sand and compost into something more civilized.  But it has to be COARSE sand.

Or maybe people have tried to amend clay with 1/4 inch of sand.  After a few rains, the soil is almost as hard as before, and they think it's even harder.  That's because they don't remember how bad it was before.  You need to get the sand up to around 30 - 40% in the soil.  Google "soil triangle".  That's why I add a couple of inches of sand to my very stiff clay loam.  For alpines and cacti, some people use nearly pure sand.  

By the way, the soil triangle also shows that pure clay cannot be turned into loam by adding sand.  The only thing to do with pure clay is to cover it with good soil, or haul it away.

Organic matter is very beneficial, but it disappears after a couple of years.  The sand is permanent. Lime is also helpful in improving soil structure in certain types of clay loam soils.

The time to do this soil improvement is before you plant a large number of plants.  That way you can do it with a tractor  with a bucket and tiller.  Once you plant, you have to do everything by hand, and it's a backbreaking job.  Sometimes I find that my amended soil is still a little too stiff in places, so I will add more sand with a wheelbarrow and a small rototiller.  But it would have been one tenth as much work if I had tilled in more sand the first time, using the tractor.

[attachthumb = 1]

Of course, none of this is must-do, life-and-death.  I do it this way because I am trying to optimize results.

Some bonus info about fertilizer elements:  
Proteins and most other components of living organisms are composed primarily of CARBON, HYDROGEN, OXYGEN, NITROGEN, PHOSPHORUS, and SULFUR. Carbon dioxide is the carbon source which, via the process of photosynthesis, is converted into larger organic molecules like sugars. Hydrogen comes from water. Oxygen comes from carbon dioxide, water, and oxygen gas. Nitrogen, phosphorus, and sulfur are all taken up by the plant roots in ionic form from the soil. ALL PLANTS NEED THESE ELEMENTS. Green plants contain chlorophyll, which is made up of carbon, nitrogen, and MAGNESIUM. POTASSIUM is a vital catalyst in many critical chemical reactions within plants. CALCIUM is vital to the development of buds and root tips, leaf development, and protein synthesis. IRON, MANGANESE, COPPER, and ZINC are needed for the functioning of plant enzymes, chlorophyll, and protein synthesis. It is very likely that all seed-bearing plants need all of the above elements. In addition, some plants utilize the following: MOLYBDENUM, BORON, CHLORINE, SODIUM, COBALT, VANADIUM, SILICON, AND SELENIUM.

Nutrient groupings:
1. The primary nutrients: Nitrogen (N), Phosphorus (P), Potassium (K) These are the three active ingredients of most fertilizers, and are all needed by all green plants. Sulfur (S) should also be a part of this group, since it is needed by many plants in about the same quantity as phosphorus.
2. The lime elements: Calcium (Ca), Magnesium (Mg). Dolomitic limestone contains both these elements. Some limestones contain only Calcium. Limestones make the soil more alkaline (less acid). Gypsum (Calcium Sulfate) adds calcium but does not affect soil acidity. Epsom salts (Magnesium Sulfate) is a Magnesium source which increases acidity.
3. The trace elements: Iron (Fe), Manganese (Mn), Copper (Cu), Zinc (Zn), Molybdenum (Mo), Boron (B), Chlorine (CI), Sodium (Na), Cobalt (Co), Vanadium (V), Silicon (Si), Selenium (Se). These are available as trace element fertilizers, as part of regular fertilizers, in compost, in fish fertilizer, etc.

SW Washington state, 600 ft. altitude

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