Matt,

I'm a big believer in trying to build the soil and make it healthy and then letting the soil feed the plants. In general, that works pretty well. If I have well-balanced soil in the right pH range for the plants I grow, the soil feeds the plants with little outside help about 95% of the time. Excessively rainy periods, (like the spring/early summer of 2007 for example, and like much of this year), can create nutrient problems though, both my clogging roots with water which can impede nutrient uptake and by leaching nutrients out of the plants' root zones.

However, with vegetables, in order to keep them producing as well as reasonably possible and for as long as reasonably possible, I think it is helpful to feed them at least a couple of times during the growing season. I try to keep it pretty simple, so my go-to foliar fertilizers usually are compost tea or liquid seaweed or liquid fish emulsion. If I am using compost tea, I normally make the enhanced version called Garrett Juice. Normally, I won't single out one ingredient like N, P or K and try to address that alone unless I am seeing physical signs that indicate those nutrients are lacking. Sometimes, when you add too much of N,P or K...especially if adding it to soil that already has adequate levels...you can create problems because your N-P-K get out of balance.

I wouldn't plant stinging nettle near the garden, and suggest you do keep an eye on your confrey too because it leans toward invasiveness. One way to increase the effectiveness of any kind of plant you grow for use as a fertilizer is to plant it near your compost pile or directly adjacent to your richest soil so the roots of these dynamic accumulators can take up the 'extra' nutrients found in abundance in those areas. Borage can get huge when grown in rich soil and with lots of available moisture, so give it lots of space when you plant it. I usually put borage at the end of a garden row so it can spill over into the pathway and hog all that otherwise empty space.

Making and using teas is simple. Soak your raw ingredient in water for a few days to a few weeks. I prefer to use a bucket with a lid because otherwise certain pests (especially June bugs and various small moths) and I prefer to keep it in the shade. Strain out the solids and apply the liquid via a foliar feeding. Foliar feedings are most effective when you spray early in the day, preferably when there is still dew on the plants.

I let the soil feed the plants most of the time, but I'll give them a foliar feeding if their growth seems to slow down at a time when it normally shouldn't, if production seems impaired compared to what I usually see, or if the appearance of the leaves tells me they are--for whatever reason--low in one nutrient or another.

In beds that have a healthy percentage of organic matter and a decent pH, fertilizer often isn't needed at all, especially if you have a natural mulch (chopped/shredded leaves, finely shredded bark, grass clippings, hay, or straw) that feeds the soil over time as it decomposes.

I think too much attention is often given to N-P-K when the truth is that healthy plants in healthy soil tend to be able to take up all the N-P-K they need just from what is found in the soil, assuming the soil has adequate oganic matter/humus. Too often, many gardeners don't think about the micronutrients, also known as trace elements, that plants need. Soil more often is lacking in micronutrients( copper, molybdenum, chlorine, calcium, magnesium, iron, manganese, sulfur, zinc and boron) than in macronutrients. The only way to know what your soil currently has versus what it needs is to have a soil test done so you know exactly what you're starting out with.

I don't know how long you've been gardening, but many people neglect to get soil tests and just add what they think their soil needs instead of finding out for sure. Once you've gardened a while and have a good understanding of your soil and of how plants generally perform in your soil and climate, you often can tell what your plants need (or don't need) just by looking at the plants. So, if you haven't had a soil test in the last 3 or 4 years, I'd recommend starting with the soil test and figuring out where to go from there. And, by the use of the term soil test, I mean a professional one. Those little soil test kits sold to homeowners are notoriously unreliable.

Having said all of that, I am not above using a chemical Bloom Booster product once or twice during a growing season to stimulate the flowering of tomato plants in a bad year when their production has been impaired by something beyond my control....like the recurring cool/cloudy/rainy cycles we had during parts of 2009 or the heavy flooding rains we had in late spring of 2004 and 2007. However, it is not a routine practice I engage in--more of an emergency measure used to ensure I'll get enough tomatoes in a given year to can/freeze/dehydrate to get us through the winter and spring.

Dawn

I agree with Dawn that a lot of people focus on NPK too much. I personally think that pH is more important because proper pH makes all nutrients more available to plants. And organic matter in the soil is absolutely critical, not only for supplying nutrients and organic acids and beneficial microorganisms, but also for improving soil structure--adding crumb and pore space. And like Dawn says, a soil test is money well spent.

I found a really handy soil testing kit at Lowes and it's turned out pretty reliable. It was around $5.00 and there's enough for about 6 testing in 4 different catagories.

Just my opinion, but DON'T PLANT STINGING NETTLES!!! They sting badly, make horrible sore spots and they're just downright nasty. My DH calls them "devil weeds".

Paula

Stinging nettles and children are a BAD combination. We thought we had them all eradicated around the house when our children were small then later saw some and trained them to watch out for them. Then a four-year-old granddaughter wearing shorts stepped off the path in the woods to look at a pretty flower and came out squailing. Where I grew up near Puget Sound stinging nettles got 4-5 ft tall but here they are only 12-15" tall.

I would think that if a particular plant is rich in a certain nutrient, it's because the plant pulls that nutrient selectively out of the soil. So if you have a patch of ground you plant in something that is rich in nutrient A, then after you're done growing it there, your patch of ground is now deficient in nutrient A. You can add the plant back to the soil as compost or mulch, but what have you gained? I'd think very little.

Unless you're growing the stuff in a spot you don't mind draining of nutrients to feed a spot that you want to be richer, it doesn't sound worthwhile.

Dynamic accumulators are plants that can mine nutrients from the soil better than other plants do, but that doesn't mean they remove all of it from the soil and leave it depleted.

Different dynamic accumulators work in different ways so you generally do not end with a patch of ground that is deficient in nutrient A. It isn't like the plants go in there like a vacuum cleaner and 'suck up' all the available nutrient or nutrients that they accumulates. I wish it were that easy and that, if diagnosed with soil that has high levels of a given mineral, we could plant a dynamic accumulator that would pull the excess out of the ground and restore the soil's mineral levels to normal. Instead, if a specific mineral is excessively high, the better bet is to employ heavy irrigation to leach the minerals down more deeply into the soil, thereby removing them from the reach of most plants.

Most dynamic accumulators work in one of the following two ways:

1. Some plants can accumulate minerals that aren't really present in large levels in the soil. Legumes work this way. Because of the way they are able to fix nitrogen, they can accumulate lots of nitrogen even when the nitrogen levels are low in the soil where the legumes are grown. You then can put that nitrogen back into the soil by rototilling or plowing those plants back into the ground, or by cutting them and leaving them on the soil surface and letting them decompose. As they decompose the minerals go back into the soil.

Legumes are considered heavy givers and that's one reason we often grow legumes like beans, which are heavy 'givers' interplanted with corn or rotated with corn which is a heavy 'taker' of nitrogen.

Legumes don't require low-nitrogen soil to grow, but they can grow in low-nitrogen soil where other plants would not thrive, and they can improve that soil and make it more suitable for other plants to then grow in.

Some of the legumes that are dynamic accumulators are clovers, alfalfa, peas, beans, and peanuts.

When you have an area of ground on your property that is severely nitrogen-depleted, it generally is the legumes that grow there naturally....because they can and other plants can't. After they've grown there a while and decomposed there, the soil's nitrogen levels can come up and then other plants will sprout and grow there.

2. Many non-legume plants that are dynamic accumulators can send roots extremely deeply into the soil and this enables them to 'mine' the minerals that exist in subsoils and which are, therefore, not available to plants whose roots remain in the upper levels of the soil. There are, however, other dynamic accumulators that are more shallow-rooted and they will remove some of their favorite minerals from upper soil levels, but they generally don't strip all of it out of the soil. Even though they are accumulators, they have a limit to what they can mine and accumulate.

Some of these plants can grow in soil with mineral levels that are toxic to most plants. So, by removing some of those excess minerals, they actually 'rehab' the soil and make it viable for a wider range of plants.

Some of this type of non-legume dynamic accumulators include dandelions, borage, comfrey, buckwheat, daikon radishes, marigolds, mints and stinging nettle. There are dozens, if not hundreds of others.

Mineral accumulation isn't the only way dynamic accumulators and other 'helpful' plants enable other plants to grow in soil. Many plants have dependent or symbioc relationships with one another and a specific plant cannot grow without its symbiotic partner. The common wildflower, Indian Paintbrush, is an example of this. Indian Paintbrush needs to grow in fields that have grama grass because the grama grass produces a helpful fungi that the Indian Paintbrush needs. You can grow Indian Paintbrush in an area without grama grass, but only if the soil already contains the mycorrhizal fungi the paintbrush needs. (You can buy and add mycorrhizal fungi products to your soil or you may have mycorrhizal fungi in your soil already depending on what was grown in your soil in recent years.) When native grasses like grama grass produce mycorrhizal fungi that the flowers need, they are functioning as a dynamic accumulator for those wildflower, but they're accumulating a fungus in the soil instead of accumulating a mineral from the soil. Sometimes people try to grow wildflower seed blends or seeds of specific wildflower varieties and become frustrated when the seeds don't sprout at all, or sprout and then die. Often, the gardener hasn't done anything wrong and the seeds themselves are viable, but the micorrhizal fungi are absent from the soil or exist in very low levels.

I believe that people who use permaculture methods rely on dynamic accumulators more than the average gardener does, and probably any good permaculture book or website would discuss dynamic accumulators and their usage in greater detail. I read some of Bill Mollison's permaculture writings long, long ago but my brain has arrived at middle age and doesn't remember all the details like it used to.

Dawn

The interesting thing about comfrey is that it's root's go much deeper than most plants. It accumulates minerals and trace elements from deep in the subsoil, so even if there was a danger of somehow depleting the the soil of nutrients, comfrey wouldn't be a problem. I've grown the "bocking 14" variety, which is sterile, so there's no problem with self-seeding. It will grow from the tiniest root cutting, so once planted, you will probably have a comfrey patch for all eternity! I hope the future residents of our house are gardeners so they can appreciate what i've done for them. :) Apparently, the comfrey leaves can also be simply cut and used as a mulch around veggies and used as an activator in the compost pile. The leaves break down very quickly...

Unfortunately, nettle does not come in a sterile variety...but i'm so tempted. I've been reading about the wonders of the nettle...in France there is a "nettle society" for nettle enthusiasts. I just need to find a place to put it... It will just take some creativity and thinking outside of the box. A plant is only a weed until you find something useful to do with it.

-Matt

Matt, I suppose maybe you could grow a patch of stinging nettle under a lightweight floating row cover suspended over PVC or conduit arches (like low tunnels) in an effort to contain the seeds....or just try to cut and use the plants before they go to seed. I'm assuming that you don't have children that might get into the nettle. We have stinging nettle in random spots here at our place although none of it is near the house, and I avoid it when I see it in the woods.

Dawn