NPK what?

     If you’ve even gardened for a little while chances are you’ve purchased fertilizer. One of the top 5 questions I’m asked is “what should I feed my plants”? Well, in order to answer that you need to understand some of the basic physiology of plants.

     First, there are two types of nutrients plants need, macro and micro. The primary, or macro, nutrients necessary are nitrogen, phosphorus and potassium, commonly referred to as “N-P-K”.  Others that are necessary in small, or micro, quantities are minerals such as calcium, magnesium, sulfur, boron and copper. In total there are 13 mineral nutrients, 3 macro and 10 micro necessary for plants to survive. Newer research has shown that there could be 11 micros, however most of the “professional” books I have say 10.

     So, NPK means “Nitrogen, Phosphorus and Potassium” right? On the bottle of fertilizer manufactures usually don’t say “NPK” but rather they represent the total percentage of each mineral in that substance in a format like 10-4-3. That means the fertilizer you’re looking at is 10% Nitrogen, 4% Phosphorus and 3% Potassium. Ok, great, what does this mean and how can I use it?

     An easy way to figure out how much of each you need is to go back to the plant physiology. Nitrogen is used by the plant primarily for foliar (leaf) production. Phosphorus is used for root and flower production. Potassium is used for fruit production and disease resistance. My simple shorthand:

   N = Leaves
   P = Roots & Flowers
   K = Fruit & Disease

     A good example would be Tomatoes. During the initial growth cycle you would want a fertilizer higher in N and P to help establish roots and promote foliage development. During the latter stage, as in the garden, you would want lowered N and higher P & K. High levels of N for things like peppers and tomatoes produces beautiful foliage on the plants but very little to actually eat.

Some common NPK’s are:

   Bone meal – 1-13-0
   Blood meal – 13-0-0
   Mushroom compost – 2-1-1
   Fish emulsion – 2-4-1

     I have found that, much like everything else gardening, simple is better. In the ground most of the micronutrients are supplied by Mother Nature, what you really need to augment are the NPK minerals. Over the past couple years I’ve settled into Daniels 10-4-3 for everything as it includes micro’s. These are critical to me since we grow primarily in pots and not in the ground.

Some good reading on the subject:

http://www.ncagr.gov/cyber/kidswrld/plant/nutrient.htm
http://en.wikipedia.org/wiki/NPK_rating
http://www.planetnatural.com/site/xdpy/kb/n-p-k-organic-fertilizers.html

And if you want to get really geeky on the subject:

http://www.ballpublishing.com/ballpub/_RedBook.aspx

Zone 5: Tomatoes From Seed

It’s January, the high yesterday was just at freezing, but it’s time to start planning for this year’s garden. Today I’m going to focus on starting tomato seeds in my zone, 5.

The first thing you have to watch out for, which I also suffered from, is starting too early. Since it’s January, this month you’ll want to go through your catalogs, order the ones you want and come up with a plan. Resist the urge to actually plant them!

When to start? The USDA says the last average frost date for zone 5 is somewhere around May 25th, personally, I shoot for a “ready date” of May 15th. Tomatoes take around 8 weeks to be ready for transplant so back up 8 weeks from May 15th and start around March 15th. A good general plan is start around St. Patrick’s Day for transplant around Mother’s Day.

The first thing you need is a spot in the house that’s decently warm and receives a good amount of sun, that is, when there actually IS sun in the winter. A south facing window is a good spot since the sun is quite low in the southern sky this time of year. If you don’t get enough natural sunlight, fluorescent lamps work quite well for supplemental lighting.

What you start the seeds in can be as elaborate or as simple as you want. I’ve seen all the way from an old strawberry containers to elaborate indoor greenhouse systems. It’s completely up to you. Personally, I like moderately simple, a 1020 flat, some inserts and seed starting mix under fluorescent lamps.

The part I can’t stress enough is seed starting soil: buy it new. Don’t use garden soil or potting soil, buy a quality seed starting mix. Seedlings are extremely susceptible to pathogens that result in what’s called “damping off”. Good quality seed starting mix has been sterilized which greatly reduces these problems. I say this having lost MANY seedlings to damping off diseases.

Perhaps one of the most common questions people ask me is “why are my tomato seedlings stretching out and are so leggy”? This is usually a combination of two things: high temperature and low light. Lower the ambient temperature and increase the light levels and you’ll find that you get shorter, stockier plants for transplant.

The second most common question is “what should I feed my tomato seedlings”? I always recommend fish emulsion at 1/2 the rate recommended on the bottle. Feed with that mixture once or twice a week until transplant.

Now, these are of course just my recommendations based on what has worked for me. If you have a system that works for you, by all means let me know!