Herbaceous Plants: Dimmock's first suggestion is to divide herbaceous plants during the winter while they're dormant. She says to divide the herbaceous plants like phlox — you can make a lot more plants out of them.
When the plant gets old and the center dies, take off sections and replant. Throw away the center because it will never regenerate. If you want to divide the clump even smaller than that, get two forks back to back and then use it to lever it apart. Dimmock says it creates leverage to make it much easier to divide the clump. Then you replant the herbaceous plant.
Variegated Euonymus: Dimmock says variegated euonymus are very effective in the garden but they're prone to reversion, or bits of them going back to just plain green. Dimmock suggests checking your variegated plants for bits of greenery because slowly they will become more dominant and you'll end up with all green and no variegation. It's also worth checking right inside the plant for more green plants that will take over in the spring.
Evergreens: Dimmock says to check over evergreens, such as fatsias and cordylines. Remove the leaves because it makes them look tidier.
Tassel Tree: Tassel trees have long catkins that will last until mid-Spring. Dimmock says if you staked the plant, now would be a good time to check that the stakes are firm and that the tree ties aren't choking the plant.
Roses: Dimmock says if you didn't prune your roses in the autumn, you really must do them now. She says to take out all the deadwood and reduce the long shoots back by a third or two-thirds and prune to an outside facing bud. This will prevent growth from congesting the center of the plant.
Dimmock says the harder you cut your roses back, the less flowers you'll get. But the bigger the rose will be. If you only cut them back lightly, you'll get more flowers, but they'll be much smaller
Wisterias: Dimmock says wisterias need their second pruning at this time of the year. So these long growths need to be taken back to two or three buds and you'll get all your flowers coming out in the spring.
Dimmock says the winter is the perfect time for hard cutting plants. She explains this method will get you plants for free with minimum work. You cut foot-long parts from your plant, pencil thickness, always slanted on one end and flat at the other so that you can remember which end is up. Plant them in a quiet corner of the garden and leave them for one year (even though you may get leaves in the spring). She says there may not be any roots so leave them alone. Next spring you can dig them up and you'll have several new clones of your favorite plant.
Dimmock says you just need to be patient ...