do not fidget with Japanese irises today. Every year this time of year it is clear to me the Japanese irises want that old thatch pulled off them, so I do it, and since they are "gross feeders," as every book says, it seems only fitting to give them a heaping mulch of rotted horse manure.

Wrong. I know of no book that tells you not to do this, but three times I have done it and had the irises die before my very eyes within a month. The thing to do is do nothing. They like extremely rich soil if they can get it, but in my experience (costly, as usual) they do not like heavy feedings this early, unless they are new seedlings, in which case they will grow in almost pure horse manure.

A plant that does not flower worth speaking of, but which is pretty in a modest stately sort of fashion, is the variegated sweet flag, Acorus calamus. It sends up sheaves of leaves that fool many people into thinking it is an iris. The plain green form is tougher than the striped yellowish-white kind but not so good looking.

For a time I thought about what to plant in a large Chinese pot glazed brown outside and blue inside. Such a pot often winds up sadly holding umbrellas, though perhaps originally intended by its maker as a fish bowl. There is something esthetically wrong with filling such a thing with dirt, over the blue glaze, but such a vessel looks silly to me if it just sits there empty. I concluded it would be all right for the variegated sweet flag. I grow the plant in an eight-inch pot and set it in the large glazed pot and fill it all up with water with a couple of tiny goldfish to eat mosquitoes. By the end of the summer the fish are rather large and must be dumped carefully into a larger fish pool for winter.

The sweet flag, which books tell you starts flopping about in July, remains rigid all season with me. I think it likes being covered with about five inches of water. If you cut the leaves (if you had a whole pond full of it, say) you get a nice tangerine smell. Otherwise it just sits there looking fresh and cool all summer, which is enough to ask.

We may expect another freeze or two, maybe a nice heavy snow or ice storm that turns everything to "a real fairyland," and all this must be cheerfully borne, since it is in the cards. We do not know anything about sharp freezes in June, which are suffered by many of those English gardens that people wrongly think would be such a delight to work in.

It is at just such a time of freezing after weeks of milder weather that one may err as I did with my pool heater. This is a floating disk surrounded by wire mesh, and it provides just enough heat to keep a two-foot-square hole in the ice, thus preventing the accumulation beneath the ice of noxious gases.

I was indignant when mine started failing to keep an open space in the ice and resolved to go right back to Gaithersburg and tell the salesman what I thought of his product. Then it became clear I had the switch in the off position. That was why it was not making any heat. I always remember "onward and upward" for the switches of my house. Push them up, they're on. The switch for the pool heater, however, is onward and downward. I am happy to discover this before making a scene at the feed store where I bought it, and I pass on a valuable tip: take a waterproof pen and write Off and On on the switch itself. This way you do not have to tax your mind to remember.

Like so many things in gardening, you will never forget such a simple matter as which way the switch works for a pool heater, just as you will never forget where you planted Primula rosea or Ligularia 'Desdemona' or the gladiolus Uncle Will sent that he said was so wonderful and it was not. But all these things will be forgotten promptly. Write them down.

Write them in a book and keep the book in a filing cabinet by your bed. You may take the book to the garden with you to refresh your memory when you are not sure whether a particular daffodil is 'Easter Moon' or one that looks much the same. Then you may take your planting chart, which you keep in your book, into the garden to identify the flower. But there is an important rule:

The minute you are through with the book in the garden, walk in the house and put it back in its filing cabinet. The phone will ring. I have learned not to answer it until the book is back in place. Otherwise you set it on the table, finish your conversation, respond to your wife's cry that something is the matter with the trout lilies, and first thing you know you forget about the book, which somebody moves off the table and it falls in the floor and the dog chews part of it up, etc.

Returning your garden book immediately you are finished with it is one of those things like shaving or washing behind the ears that takes time, but which you must not allow the phone or anything else to interrupt, lest you wander off on some other project and forget entirely.

I am ashamed this is so elemental, about the switch being on and the book not being left around loose. It has taken me half a century to learn these things, and since there is little else I really do know, I take the liberty of passing my wisdom here along to you.