Some of the following things I have learned over many years of gardening, and some are tips garnered from friends and acquaintances. I hope they will be of help to you.  I will add more in different categories from time to time.

General

1. Tree roots spread wide, of course, but did you know that the spread is usually one-and-a-half times the height?
2. When some blooms finish, they can look like another bud and you’re not sure whether to dead-head them or not. The dahlia is such a flower: when the bloom has finished, it looks like a conical bud; the new bud is round.
3. Select small daffodils for small gardens. There are many species and varieties to choose from. The dainty look of many will be much better than any number of larger ones.
4. When planning a new garden design, put evergreens in first so that you have the general shape and substance of the look you want.
5. Don’t despair about a tree stump being difficult to remove. Make it part of your garden design: drill some small pot-sized holes, plant the pots with some colorful plants (trailing ones are lovely for this), surround it with small, dainty or low-growing flowers, and–-presto!-–you have another interesting feature. If the stump is in a shady patch, you might even be able to persuade various mosses to reside on its bark.
6. Remember to search through driftwood for some interesting shapes. These decorate walls and fences with beauty, sometimes humor. After shaking out any obvious bugs, they may need a good scrub with warm water and a little bleach; this will ensure you are not transporting viruses to your garden.
7. When watering plants in greenhouses during the winter, take off the rose from the watering can. This will direct the water to the soil, rather than to the leaves. Do not water much during this period as plants fare better when drier in the winter.
8. Add some lighting for the garden – spotlights, lanterns, for the pond or swimming pool, for steps; and, remember, solar lights are excellent.
9. When planning a greenhouse, don’t forget to put in some cold frames, too. They are extremely useful during the winter and spring for sheltering some plants, and for giving a good start to others. However, make sure they are well ventilated; at times, the sun may be too hot and damage the plants inside.
10. I have not tried this, but I am assured that garlic, planted with roses, has an excellent effect: the roses take the garlic into their roots and greenfly don’t like the taste!
11. If you have a tree you are fond of and which is looking poorly, no matter what you do, get an arborist to check it for you. They have the right equipment to drill into the trunk which meters whether the tree is hollow. They will also measure the health of the tree and advise the best treatment. It is money well spent.
12. Save plastic drinks bottles and puncture a few holes in the bottom. Then, when you are planning a short trip, or when the weather is really hot, fill the bottles with water and sink them a little way into the soil of your hanging baskets or other potted plants to keep the soil moist. Since the roots of mixed plantings reach different depths, it is important to maintain an all-over moisture at the same level, particularly with hanging baskets which dry out faster.
13. My own view: the garden should be the clothing to dress the house. (I think our Style Expert, Michele Benza might agree!)
14. And.... sometimes you just need to be guided by your own instinct, no matter what the experts say. After all, it’s your garden, in your area, isn’t it? Don’t be frightened to try your own remedies; just watch and study what’s happening to your plants.

You may well have some tips of your own to share; write to me and I will make sure they are passed on to others.