Allendale, Northumberland: Their sheer presence makes them a source of delight, and they've taken root in unlikely places. Now it's time to collect their seeds

In the first storm of autumn, their huge, pliable stems rock and sway, but none are toppled. These hollyhocks, grown 10ft tall since spring, are survivors, delighting me for many months. I'm loth to cut them down, shrivel-leaved as they are, because they still give so much height.

My grandchildren ran between them in the summer holidays. Red admirals and peacocks settled on their floppy petals. Bumblebees nosed up into their large flowers, sheltered from the rain by the downward facing trumpets of hibiscus-like blooms. Angle shades moths came to the light of the moth trap, their caterpillars having fed on hollyhock leaves.

Single-flowered varieties of hollyhock such as these, Alcea rosea, have nectar and pollen, but not the froufrou many-petalled doubles. Guided by fine lines to the centre of the flower, insects suck the sweetness from nectaries that sit at the base of the sepals. These appear as a five-pointed star made visible by gaps between the base of the petals. Bumblebees get liberally covered in pollen grains from a central bottlebrush of anthers and stigmas, both of which mature at different times to ensure cross- rather than self-pollination.

Leaving my hollyhocks to go to seed means they suit themselves where they grow. Some have settled between the gaps of the terrace where there's poor compacted soil and rubble. One has completely lifted a heavy stone paving slab with its vigorous growth. They all developed rust disease, so I reduced the leaves to allow air to circulate since I don't use fungicide.

Their seed is now ready to harvest and I collect it when dry to store in paper bags. Each seed case wrapped in five sepals is a little parcel with a twisted top like dim sum. As the tops relax, they open to reveal a circle of dry seeds stacked vertically like coins. I'll pass them on to friends who requested them for their gardens.

A few sparse flowers hang on, their petals tinged brown but still protecting grainy pollen. On this October day, a heron shrieks as it flies over the garden and there's the chatter and yak of jackdaws delighting in the high winds. Wild days, the first frost and seed collecting - these are autumn days.

Country diary: Giants of the garden, our hollyhocks grow where they like | Susie White