By Ashley Walker
Copyright (text and images) Nature’s Rainbow. October 22nd 2022

Autumn is often a time of neglecting the garden after a busy year. It was not always thus. Autumn used to be a popular time for planting winter hardy biennials and perennials for flowering in the following year. Here is a list of jobs you can do now and later during the winter to get prepared for next year. Jobs done now will save you time and ensure the best possible display of dye plants in the Spring and Summer

Plant any Weld seedlings you have been ‘growing on’ in pots or modules and sow direct into any waste ground.
It’s getting a bit late to sow Weld seed but if you have collected substantial amounts earlier in the summer and have some bare soil in your garden, or if you know of some disturbed waste ground which is unlikely to be used in the next 10 months it’s worth giving it a go. Only a tiny number of seeds need to make it through to mature plants to give you a good harvest next year. They will grow slowly through the winter and early Spring and will be ready to flower in mid-Summer. Just sprinkle the seed onto the surface.

Note: although Woad is also a biennial which usually germinates in the Autumn I don’t recommend sowing it now as you want to harvest first year leaves for as many months of next year as possible. If you sow it now it may flower next year and you lose the young leaves for dyeing.

Harvesting any remaining dye plant material

Most plants are now dying back but Woad is probably still going strong and there’s still plenty of time left to harvest the leaves. The amount of indigo to be extracted may have reduced a bit, but the leaves will produce a satisfying amount and will continue to do so all through the winter. If you are finished with this year’s Woad plants pull them up, leaving only 2 or 3 plants to produce seed next year. There is an argument for leaving this year’s plants in over winter (so long as you don’t need the space) as the early flower stalks (before the flowers start to mature) and leaves also produce good indigo. If you have lots of self-seeded Woad coming up, treat it like a weed and pull it out – then use it in an extraction bath.

Seed saving

It never ceases to amaze me that most seeds, despite getting rained on for days at a time, usually do not germinate while still in the flower head. This does occur with some plants like Teasel, but I have not seen it on any of the dye plants we grow.  Seed saving is a task for the whole of the summer but now is the time to harvest Madder berries and Japanese Indigo seed. You may also still have some Dyer’s Chamomile and Dyer’s Coreopsis in flower which will still be producing seed.

Madder berries should be picked and dried on a tray or on newspaper on a sunny windowsill or in an airing cupboard, until they are quite dry. The outer flesh of the berry can be removed before drying to speed up the process. Dried berries can then be stored somewhere free of any damp and sown in Spring.

To collect Japanese Indigo seed look carefully at the flowering heads and pick those that have started to go brown. Very often a flower head will contain new flowers and also mature seed at the same time. The seed is usually wrapped in a brown casing which is the remains of an old flower. Sometimes you can see the black or dark brown seed emerging from the old flowers.

Spread out the flower heads on newspaper or a tray and leave to dry on a sunny windowsill or similar spot. When the flower heads are dried they can be rubbed gently between the fingers or the palms of your hands to release the seed. Then carefully blow the chaff to one side while gently shaking the tray from side to side. The heavier seed will tend to stay put while the chaff is blown to the far end. Many seeds will retain the brown flower covering but that’s fine, they will still germinate. A variety of kitchen sieves with different size mesh can also help with cleaning the seed. Often there are numerous small immature or unfertilised seeds in the flower head which can be removed in this way. Variations on this method can be used to clean many different dye plant seeds but Japanese Indigo remains one of the most difficult seeds to clean.

Removing any dead plants

This is optional and really depends on how tidy you want your garden to be. Untidiness is good for wildlife but your paths may need clearing of overhanging dead plants for access, so some tidying is a good idea. Hopefully you will have a compost heap where you can place any dead material. If you can, add some vegetable kitchen waste to help to rot it down. A supply of your own garden compost can be a vital ingredient to long term soil fertility.

Weeding and mulching

Well you know it! At this time of year the weeds are going ‘hell for leather’ making up for lost time during our long hot and dry summer. They are also taking advantage of the new growing space being vacated by some of your now declining dye plants. Many fast growing weeds can produce seed throughout the Winter which will make your life difficult come the Spring, so try to keep them under control either by weeding or spreading mulch on the bare soil surface around your plants. But remember if you use mulch you will also be preventing some of your dye plants from self-seeding e.g. Weld and Saw-Wort.

Adding manure/mulch to madder and other Rubiaceae and herbaceous plant beds.

Once the Madder has died down completely (in January) spread a thick layer (about 10cm) of manure or garden compost on the bed. This will act as a weed suppressor and will add nutrients to the soil to help the Madder grow in the following year. If any grasses have invaded the patch try to pull them out while the Madder is safely dormant. New shoots will grow through the manure or compost without any problem. Other herbaceous plants e.g. Murasaki, Golden Rod, Dyer’s Woodruff and Lady’s Bedstraw will also benefit from this treatment.

 

Protecting plants from frost

You may be growing some perennials which are only semi-hardy. This means they may be damaged or even killed by a hard frost. Plants which fall into this category are: Coreopsis grandiflora, Coreopsis lanceolata and Rubia peregrina (Wild Madder). If you cannot move these to a protected location (cold frame, greenhouse, polytunnel etc.) then you need to keep an eye on the weather forecast and if there are harsh frosts due try to cover your plants with horticultural fleece or bubble wrap. If you are in part of the country where frosts are rarely a problem e.g. London and the South West coasts of England and Wales then you should be OK. There follows a rough table on forecast night time temperatures which may come in useful particularly to Japanese indigo growers who want to leave their plants as long as possible before final harvest of leaves or seed.

The further North you are the more likely it is that even mild frosts will be damaging simply because the nights are longer.

Forecast degrees of frost

6ºC	If the forecast is for a clear sky during the night with no breeze or wind then there is a small risk of a mild ground frost. Probably not enough to do any serious damage to frost sensitive plants like Japanese Indigo.
5ºC	Again with a clear night sky and no wind there is a chance that tips of leaves may become damaged if there is a frost.
4ºC	With a clear night sky, damage to Japanese indigo is very likely and outer leaves may be killed. If the weather is windy and the sky cloudy all night, the chances of a damaging frost are still low.
3ºC	Increasingly likely that damage could be extensive but Japanese indigo unlikely to be killed outright. A cloudy night with some wind will protect plants.
2ºC	Danger that Japanese Indigo could be killed outright by a frost particularly if the night is clear and there is no wind and the plants are growing in an exposed area.
1ºC	Most plants of Japanese Indigo are likely to die during a frost at this temperature, even if some survive the damage will be almost total.
0ºC	All your Japanese Indigo plants likely to be killed at this temperature particularly if they are in an exposed area. Risk that semi hardy plants would also have leaf damage.
-1ºC and below	Japanese indigo plants wiped out and potentially serious damage to semi hardy plants

Note 1: Wild Madder, though an evergreen, is capable of growing back from the roots if its foliage is badly damaged by frost.

Note 2: These forecast temperatures are based on Met Office predictions and the resulting experience of consequences is based on our own experiences across three sites in Hitchin, North Hertfordshire which is approx. 50m above sea level.