On the plot: March means be prepared

Sedum heads with frosty tips

If you didn’t tidy your beds in the autumn, get going now. Some of us leave our plant seed heads through the winter. The Royal Botanic Gardens at Kew leave sedum heads standing stark and tall until spring. Only then do they cut them back to expose new growth.

Once your borders are tidy, cover with a thick layer of mulch. Most flowering herbaceous plants benefit from added organic matter in the autumn and again in the spring. However, a word of warning: go sparingly with drought tolerant sedum. It is tough and too much goodness may encourage it to flop later in the year.

A dollop of manure on any dahlias left in the ground over winter will help protect the tubers from late frosts.

Our plots have suffered severely from carrot fly and allium leaf miner recently. Blight is a constant threat to potatoes and tomatoes. I’ve decided to have one more try at beating the pests.

‘Resistafly’ and ‘Flyaway F1' carrots claim to be delicious and literally keep the fly away.

I’ve found no leeks or onions resistant to those horrid maggots that can ruin an entire crop. Companion planting and horticultural fleece are the best deterrent. Crop rotation is vital as the pupae may be in the ground from a previous year.

‘Sarpo Mira’ potatoes claim to be slug and blight resistant, this late maincrop potato is still in the ground in mid-late summer when blight is rife. An early maincrop variety ‘Kifli’ has the advantage of being more resistant to drought than most potatoes, as well as fighting off blight and potato virus.

I can’t abandon my favourite tomatoes. I grow these on the balcony at home. This year I am going to try blight resistant varieties on the plot. ‘Crimson Crush’ is completely blight resistant and suitable for a container or in the ground. ‘Ferline F1’ has some blight tolerance and is also resistant to fusarium and verticillium wilt. ‘Legend’ is a bushy, beefsteak variety and holds the RHS Award of Garden Merit.

Trays of annual seeds adorn my window ledges in March and April. Half-hardy antirrhinums (snapdragons) are fun for children to grow. A neat row arrived on my plot last year, whether brought by a bird or the wind, they gave me months of pleasure and were a delight in a vase at home.

I’m ordering a variety for a splash of colour this year.

It’s not too late to prune roses. Getting rid of dead or any tangled wood will help protect the plant from disease. Roses are resilient and will come back stronger for a severe cut back. 

Follow our useful guide to pruning roses here

The pots of iris reticulata have been a disappointment this year. I took advice when visiting the RHS Spring Show a couple of weeks ago.

The diagnosis was simple. I believed bulbs were tough nuts, content with a bit of regular watering. I have been washing any goodness in the soil straight out of the pots. My iris may have been crying out for liquid plant food.

From behind her stand, a carpet of blues in all hues, the expert asked me: “Would you blossom if no-one fed you?”

Joanna Cruddas lives in London and gardens at her plot in Fulham Palace Meadows Allotments, on her balcony, and in her window boxes. She is the author of The Three-Year Allotment Notebook with photographs by Edwina Sassoon.