A Thoughtful Present
One of the best presents my youngest daughter gave me, years ago, was a medium-sized lined notebook with a hard cover, on the front of which was embossed the title My Garden Diary.  Inside she'd pasted, on various pages throughout the diary, various cartoons to do with gardening, some of which had been cut out from various magazines, others she'd drawn herself.  One of her many talents.  But most of the pages were left blank, for me to fill in.
 

​Gardeners & Time

And for many years, I used it religiously.  You see, gardeners tend to focus on the present, and think to the future, imagining what their various seeds or cuttings will look like in the weeks and months ahead, and what fruits they will eventually produce for their dining pleasure.  But gardeners also need to look behind, to take on board their successes and mistakes of the past. We tend not to do this. 
 

Other primates seem to understand this concept of the past:
​"The gorilla’s] trainers conceived of the past as behind them and the future ahead. But [the gorilla’s] behaviour seemed to indicate that she conceived of the past as in front of her – because she could ‘see’ it – and the future behind her – because it was still invisible. Whenever she was impatient for the promised arrival of a friend, she repeatedly looked over her shoulder, even if she was facing the door."
                       From Congo, by Michael Crichton, 1980

The Ghost of Gardens Past

​​To the natural world, the past seems to be much more real than the future. And in the old cliché, you need to learn from the past (or history tends to repeat itself).  So too with gardens.  We need to learn from our gardening mistakes and failures of the past, and build on what successes we've managed to achieve in the years before.  A diary puts your garden’s past in front of you.  Naturally.  It becomes a record of what you've  done in your vegetable patch, and when, and what the results were.  It becomes a valuable source of information that is unique to your garden.  
 

​Know Your Own Micro-climate

There is only so much that a gardening book or magazine can tell you about growing things. Its readership has a generalized national or international context. Your own vegetable/fruit garden is a unique place, a specific micro-climate within a larger local climate, with its own individual composition of soil and combination of sun, wind and shade.  
 

​For Example

You will forget what types of tomato or lettuce or carrot seed you sowed last year, and just how successful each of these were.  Past planting events become even more forgettable if you used more than one seed type for some of your vegetables.
 

So, the next time you sow a row of seeds, record the type of seed it is, the date of sowing, and the weather conditions, and other factors.  As examples, here are extracts from my 1999 diary:
30 JAN – sowed 2 trays of Johnson’s Bedfordshire Champion Onion seeds (cooking onions) inside the dining room, behind French doors.
31 JAN – sowed ‘old seed’ peas (3 trays), 1 tray chicory (very old seed) and 1 tray of new-seed leaf lettuce.
7 FEB – New lettuce germinated. Move to greenhouse in the garden.
21 FEB – onions have now been ‘up’ for about 1 week, but only 7 peas germinated.  I soaked the remaining seeds overnight and put them back in the same seed trays.
20 MAR – moved the germinated ‘old peas’ outside into the garden (not nearly enough) and sowed a new package of Early Wonder peas directly outdoors.  Temperature about 60 degrees (and sunny). Probably best to stick with new seeds in the future.
 

​Diaries, Analog, Digital & Literary

You get the idea.  How much detail you record depends on you, of course.

Instead of a notebook, you could always create your own electronic garden file in Word, and scan in articles, cartoons, excerpts of relevance, or photos of your own plants at various stages.  I habitually set my digital camera to ‘date’ my photos, to make recording easier.
 

After a few years I think you'll find that your garden diary becomes not just a record, but a treasure chest of garden knowledge, one that you'll enjoy re-reading just for its entertainment value.  And, if you can learn from your past mistakes, you might even save yourself some money!