The flowers we call herbaceous perennials tend to survive winter as roots and storage organs underground. Their leaves, stems and flowers die off in autumn, either flopping back to the ground or remaining as dried out skeletons (which can be very attractive) over winter. There are a few simple practical tasks we can do to get the most out of them each year.
SUPPORTING STEMS AND LEAVES
▼ Creating plant supports, crucially when the shoots are young each spring and before the plants have started to collapse, will help you maintain order throughout late summer and autumn. A bamboo cane or pea sticks poked in the soil will often suffice, but I would recommend hoops or structures through which the plants can grow. Clever design of a border helps, too, with strong plants next to flop-prone ones for support.
PLANTING
▼ The best time to plant is in the spring or autumn, when the weather is mild, there’s warmth in the soil, and a good chance of rain, which is so crucial for establishing plants. A word of caution, though – in recent years we have had very dry springs, so I now tend towards the wetter autumn when planting.
Take care to get the level right: the soil level should usually be where the roots join the stems. This is called the plant's crown.
MULCHING AND FEEDING
▶ Although perennials usually require a lot less input than annual plants, over time they can get stressed as they use up resources in the soil, especially after they have bulked up to a much bigger size than when originally planted.
A mulch of organic matter such as homemade compost or well-rotted manure helps to keep weeds down, improves the soil’s ability to hold moisture and adds vital nutrients. It’s best to add 5-6cm to the soil around your perennials each winter or spring.
CHELSEA CHOPPING
▲ In late spring (around the time of the RHS Chelsea Flower Show) you can cut back late-summer perennials by around a third. This does two things: firstly, it promotes branching in the stems so that they are bushier and less likely to topple over later. This delays flowering a little, and usually results in slightly smaller but more numerous flowers, so again there is less chance of the stems flopping over as we head towards late summer.
PROPAGATION BY DIVISION
▼ One of the easiest ways to make more perennials is by dividing them. This involves digging them up from the border, (as
