'Autumn Blaze' maple at Bernheim Arboretum in Clermont, Kentucky

Dear Grumpy Gardener,
 
Why do I find some instructions saying when I plant my tree, I should not amend the soil with any compost, peat, other soil, or fertilizer? It says to  backfill with the soil that was removed from the hole. Other times I have read to mix the removed soil with all sorts of things to loosen it up. I have a bag of Tree and Shrub garden soil.

Do I or do I not use it to plant my beautiful 10 ft. Autumn Blaze maple? Jo

Grumpy says:

Here is why I don't believe in amending the soil when planting a shade tree like 'Autumn Blaze.' Many people think that the root system of a tree is a mirror-image of its trunk and branches. It's not. In fact, the root system of most trees looks pretty much like a pancake spreading far beyond the branches with the vast majority of roots in the top 6 inches of soil.

What's this means is that the roots don't stay in a tiny hole of amended soil. They spread out into the soil you have. Amending soil may actually inhibit root growth, as roots don't like growing from one type of soil into another. So what you should do is this:
 
1. Dig a hole at least three times wider than the root ball, but no deeper
2. Plant the root ball so that its top inch rises above the soil surface
3. Backfill around the root ball with loosened soil you dug out
4. Water thoroughly to settle the soil
5. Cover the top of the root ball with mulch.
 
The tree probably comes with slow-release fertilizer added, so there's no need to add more now. In the future, fertilize the tree by sprinkling tree fertilizer on the soil surface underneath the branches, but not up against the trunk.

Yet Another Reason I Resent My Son

This is my 15-year-old son, Brian, and his date for the Homecoming Dance, Savannah. I told him to make sure he picked a cute girl and he obviously followed instructions. So why am I resentful? Because I didn't have a date until I was 38 years old. Oh sure, eventually I married a hottie, but there were 25 lost years in the meantime. What a tragic loss for all of femaledom!
 

Clay soil curses most gardeners in the South. It drains poorly, dries hard as a rock, and restricts the movement of air, water, and plant roots. It's a pain in the butt to garden in. So naturally, we look for things we can add to it to loosen it up and save our aching backsides.

A lot of people think you can loosen up clay by mixing in lots of sand. It's sounds logical. After all, among all the constituents of soil, clay particles are smallest and compact the most, while sand particles are biggest and compact the least. Adding lots of sand will therefore break up that clay, right?

Wrong, wrong, wrong, rototiller-breath! Sand mixed with our Southern clays forms a sort of nasty concrete. When it dries, just try digging in it. You can jump from a tree onto the shovel blade, but the blade won't move and you'll lose your dentures.

Instead of adding sand, add organic matter -- lots of it. Any kind will do -- sphagnum peat moss, garden compost, composted cow manure, grass clippings, chopped up leaves, chopped pine bark, potting soil, worm castings, whatever. Organic matter coats the clay particles, opening up pores in the soil through which air, water, and roots can freely move. It also makes the soil comfy for earthworms and other organisms that loosen the soil even more. 

So forget sand. Add organic matter to your soil every year, in gross quantities if you can. Organic matter can turn even the worst clay soil into good soil within a couple of years.

The Grump hath spoken!  

                                                                                                                            Photo by Jared.

OK, how many times have you heard people say something like this? "Be sure to keep poinsettias away from children and pets, because they might eat the leaves and get poisoned."

Poinsettia or Poison? Hold Me, I'm Scared!

Poinsettias are NOT poisonous. The milky sap might not look appetizing (which is why very few sentient people would actually eat the leaves), but it won't kill you. In fact, according to Poinsettias: Myth & Legend by Christine Anderson & Terry Tischer, you could eat 500 leaves and the worst you would suffer is a tummy ache. That's nothing compared to the suffering of the poor plant that donated the leaves.

Look, I'm not suggesting adding poinsettia leaves to your mesclun salad, but there are far more toxic plants around your house and garden (dieffenbachia, angel's trumpet, Chinaberry, castor bean, mountain laurel, rhododendron, hydrangea, Japanese yew, oleander) and you don't give those a second thought.

No one has ever died from eating a poinsettia. The KGB has never bumped off an enemy agent by giving him a poinsettia. So stop spreading this stupid myth! And while you're at it, stop repeating that Tiger Woods was raised by tigers in the woods! (He was raised by a very nice panda.)

Grumpians, it has come to my attention that many weekend gardeners are wasting their precious time and money following stupid advice that has no basis in science. Therefore, every Friday from now until I feel like stopping, I'm going to debunk some popular myth for the benefit of you, my loyal readers.

Question -- My lawn service says I need to apply a high-phosphorus fertilizer this fall to encourage a vigorous root system. Is this true?

Answer -- Only if you're employed by a lawn service and make a living getting as many people as possible to do things that aren't necessary.

Every hort and agronomy student remembers learning that the three most important plant nutrients are nitrogen (N), phosphorus (P), and potassium (K). This is the order in which percentages of each are listed on the fertilizer bag. For example, 16-4-8 means the fertilizer contains 16% nitrogen, 4% phosphorus, and 8% potassium.

Nitrogen and potassium are water-soluble and readily leach from the soil following rain or irrigation. Thus, they must be replenished periodically for proper growth of lawn grasses and other plants. Phosphorus, on the other hand, stays put. It binds with other minerals in the soil. The phosphorus you put down last year is almost certainly there this year.

The only way to really know whether your soil soil needs additional phosphorus is to have your soil tested in a lab. Ask your local Cooperative Extension service for a soil test kit (it won't be free, but it's not expensive). The vast majority of soils in this country have all the phosphorus they need. Excessive levels of phosphorus can make other important nutrients, such as iron and zinc, unavailable to plants.

Most of the phosphorus sold in this country is mined in Florida. Not coincidentally, most fertilizers formulated for Florida gardens contain little or no phosphorus.  

High-phosphorus levels in "bloom-booster" fertilizers are a waste too. Regular garden soil doesn't need it and you won't get any more flowers. Oh, it may make some sense to use a  high-P "bloom-booster" fertilizer on plants grown in sterile potting soil once, but after that they have all the phosphorus they need.

What have we learned here? That most likely, your lawn and garden already has all the phosphorus it needs. The best thing you can do for your plants is work lots of organic matter into the soil. And use a composting mower if you have one.