As a new series of The Great Gardening Challenge begins, Mark Gregory tells Hannah Stephenson how to boost those borders without breaking the bank.

Worried that doing up your garden will cost a small fortune? This doesn't have to be the case, says garden designer Mark Gregory, one of the judges on Channel 5's The Great Gardening Challenge.

Armchair gardeners tuning in to the new six-part series this month will see horticultural professionals competing against each other, as they perk up neglected open spaces and transform them into gorgeous gardens in just 48 hours on a budget.

The show, presented by Diarmuid Gavin and Nicki Chapman, will surely provide inspiration for amateur gardeners, whose own budgets may be more restrictive than those of the TV pros. And with a creative approach and some insider secrets, it's certainly possible to perk up your plot without having to break the bank, as Gregory believes.

Here, he shares eight money-saving tips for budget-conscious gardeners...

1. Get plants for free

"Digging up and dividing plants is a way of getting plants for free," says Gregory. "In your own garden, plants can often be lifted and separated to double up the numbers. And if you have close family and friends, you can get plants from other sources as well."

Plants which will grow relatively quickly and are easy to divide include alchemilla, astrantia, achillea and sedum.

2. Buy small plants

Cranesbill geraniums will spread quickly (Hannah Stephenson/PA)

"If you are buying herbaceous plants, buy them in small pots," he suggests. "Buying herbaceous plants in big pots is a complete waste of money. Buy plants like (cranesbill) geraniums and alchemillas - standard garden plants - in p9s (9cm) or 1 litre pots. There's a school of thought that believes they will get established quicker.

"Shrubs and choice plants should be as big as you can afford, to make an impact, but your smaller infill plants don't have to be."

3. Don't plant in winter

"Either plant late summer or spring, after the bad weather, when the plants have more chance of becoming established. You have more chance of losing plants to bad weather if you plant in November or December, when you get more frosts. If you are going to buy small, herbaceous plants, you will save money like that."

4. Check out sale plants

"There's nothing wrong with sale plants," Gregory notes. "Also, go to car boot sales to look for bargains." Many perennials in garden centres will have gone over and may look a little bedraggled, which is why they are in the sale, but they will come back next year.

5. Don't impulse-buy

"Avoid being seduced at the point of sale in garden centres, because garden centres get plants in which look great and then people impulse-buy. The result is that their garden becomes diluted by impulse buys which may not match the style of the garden or the plants they already have.

"Consider the look that you want and consider the plan. Make a list before you go and stick to it. Don't put odd bits and pieces here and there because all you get is a blancmange of a garden."

6. Plant more than one at a time

"A lot of people will plant one of this and one of that, which will create a weak, watered-down effect. Planting works best in multiples. I'd be planting in threes, fives, sevens, nines, twelves, to get something going.

"Get into the mindset that it's better to plant smaller, but more of them," Gregory explains. "Always think about repeat planting. If you have a border on the right hand side, repeat it on the left, but maybe in a smaller quantity, so the planting flows from one border to another. You can do that with plants which you've divided.

"I've seen planting done on a huge scale but only using 13 species, but because they repeat them you get a rhythm going and from a design point of view it works a lot better."

7. Stick to the rule of right plant, right place

It's no use buying a beautiful plant which requires full sun and light soil, if you are intending on planting it in clay soil in shade.

"A lot of wasted money is used in impulse buying, where people like the look of it in the shop, don't read the plant label and then put it where it doesn't want to be," says Gregory.

8. Upcycle old bits and pieces

Stripped down, bare and shabby chic is the look of the moment for younger couples, says Gregory. He suggests people scour landscape yards, or fish through old skips for ephemera, second hand furniture and paving which can be upcycled into the garden.

"You can buy second hand council paving slabs and do something sexy with that. You can do things in a creative way very cheaply. You have to do the legwork, but with social media and the internet, the world has become an incredibly easy place to source things."

The Great Gardening Challenge begins on Channel 5 on Tuesday, July 2.