Planting out cosmos into the border

Planting Out Cosmos into the Border

Planting out at the right time and in the right way will really help your plants thrive, and there are a few simple tips to get this right. In this lesson, we'll also explore how you can use half-hardy annuals such as cosmos to boost your borders.

Extending the Season of Interest in a Border

Even though the border looks full, there will be gaps. I've just pulled the forget-me-nots out as they've finished flowering, and I lost some plants in the cold winter, so I'm glad to have the cosmos to fill the gaps.

By interspersing half-hardy annuals into an established border, such as cosmos, Nicotiana and zinnias, you're extending the flowering season and adding an extra layer to your border.

• They'll start flowering in June and with frequent picking, will go on until the first frosts.
• It's important to keep picking or deadheading to maximise the flowering season.

It also means you can create different colour or flower schemes each year if you want to.

• I change the colour of my cosmos to give the border a different feel from year to year. Two of the varieties I use are 'Kiiro' (pale yellow) and 'Dazzler' (dark pink).

How to Know When to Plant Out

Planting out at the optimum time is important. Leaving things in their pots for too long is detrimental, so keep an eye on them. They will still recover, but it will set them back, especially with sweet peas.

There are three things to look out for when judging whether it's time to plant out.

1. Roots should be coming out of the bottom of the pot, and when you take the plant out of its pot, there should be a good rootball.
2. However, the roots shouldn't be so congested (potbound) that you can hardly see the compost at the bottom.
3. You should plant out before any signs of stress from nutrients running out, such as yellowing of leaves.

Waiting for Optimum Weather Conditions

For half-hardies, you have to wait until after the last frosts. The weather and soil needs to have warmed up.

• I plant out the cosmos that I sowed in March between the end of May and mid-June.

Hardy annuals can be planted out a bit earlier, but avoid planting before a big rain storm, cold snap or heatwave.

• It's really important to keep checking the weather forecast.

How to Plant Out

1. Pinch out the tops, even if there's a flower bud – helps to make a bushier, more stable plant.
2. Mix some homemade compost into the area of soil where you'll be planting, to replenish nutrients, retain moisture and maintain good soil condition and structure.
3. Water in well.

Watering Established Plants

Water plants in as soon as you've planted them. After that, water regularly while they're becoming established. Spot-water rather than watering the whole border to save water. Once fully established and blooming they shouldn't need watering unless showing signs of wilting.

• It's worth installing a water butt (or more than one) to collect rainwater to use for watering and save mains water, which is better for the environment and your wallet.