Medicinal tree and shrub propagation
The power of seeds and celebrating National Tree Week!
From late summer the seeds just keep coming! I have barely finished scroffling (is there a better word?) the dried fennel seeds from their stalks. Saving seed is a joyful exercise. It is especially fun when seeds present themselves unexpectedly. This last week I have spotted hibiscus and common buckthorn, the seedheads browning and berries ripening to indicate that seeds are available now! In this post I explain more about my approach to seed saving and how I harvested seeds of hibiscus and common buckthorn, both of interest as useful plants and deserving of wider recognition.
My awe of the power of seeds goes back to my suburban schooldays. I’ll never forget the first few lines of our school song – we stood in rows and dutifully sang ‘The oak lives long, long live the oak’. Somewhere in the rest of the long-forgotten verse was the amazing fact that the mighty oak had grown from a tiny acorn. The incredible potential of the acorn as a seed impressed me then and continues to blow my mind. Now I take every opportunity to collect seeds, not only from herbs in the garden and vegetables at the allotment but also seed discovered on foraging walks. The seeds of quite a few introduced species can be collected if you notice them at the right time, many are ornamentals that have naturalised in gardens and parks.
Collecting seed suggestions
Always choose good tree parents if you can, try to avoid polluted areas and plants that appear to be diseased or very old. You should make sure that you are allowed to take seed from a site, and never remove all seeds, just a few are likely to provide more than you can use, leaving plenty for extra plants and wildlife. While it is illegal to uproot many wild flowers in the UK it is not illegal to harvest seed. And it is important to be clear about the purpose of gathering seed, since introduced and ornamental species should only be destined for cultivated or managed sites. I don’t recommend spreading non-native species in wild or unmanaged areas.
It is always advisable to let seeds mature as much as possible on the plant. Mostly it is obvious when seeds are ready for harvest as the fruits, capsules or pods start to colour up or become brown and dry, from summer towards the late autumn. It is best to monitor this for as long as practical, either you will see that fruits are fully ripe or beginning to fall (such as crampbark, elder) or seed capsules are starting to split open (such as willow).
Try to avoid picking up seed from the ground as it may have deteriorated due to moisture or disease. Spreading a tarpaulin on the ground to catch seed may be a way to avoid this. Ripe fruits or capsules should readily twist off with your fingers, or if not quite ripe then use secateurs to snip from the branches (using care to avoid damage to buds and fingers)! Some plants have to be harvested early to avoid being taken by birds, insects, squirrels, so cut off the fruiting parts and put them in paper bags to finish ripening. Always label the bags - the contents will quickly become unrecognisable!
For other plants the seed maturation process can take a while longer, for example on the Virginian witch hazel (Hamamelis virginiana) the seeds sit in a capsule for a year or so before it bursts open and blasts the seeds yards away from the parent. This is a process of ‘dehiscence’ where the plant seed capsule splits, often explosively.
Cleaning seed
Seeds need to be cleaned for further storage or use. Seed cleaning is an ancient skill, requiring careful removal of the outer coverings of ripe berries or capsules. There are some interesting words attached. Perhaps ‘scroffling’ is not a real word for cleaning seeds but I like the term ‘shucking’, a word meaning to remove the husks - especially of corn and nuts. It derives from the 'shuck' or outer covering of beans and maize, and seems to be mainly in American use. Other wonderful Old English terms include the 'cod' for a pea pod, 'shale' as the shell of a nut or peapod, 'hulk' for the husk of fruits or grains, and 'silicle' for a short seedpod. There are plenty more such terms in the Oxford English Dictionary, though sadly now historical and in need of rediscovery!
Dried seed capsules can be cracked open and crumbling of husks and pods is done by hand. But do protect your hands with gloves as some capsules such as the motherwort (Leonurus cardiaca) are remarkably sharp and spiny. Splitting pods and cones can be gathered in brown paper bags to collect the seed as they fully open. For larger quantities the dried material can be placed in a pillow case and (gently) crushed with a rolling pin. Winnowing is the process of blowing off lighter chaff and seed coverings, allowing heavier seed to fall downwards. I have found it is a skill that has to be practised using a hairdryer before committing to the windy outdoors.
For seeds in berries and fruits, add them to water and swirl around in a bowl, loosening and mashing the pulp to release the seed. Healthy seeds usually sink to the bottom. Pour off floating pulp and dead seeds, and repeat till only seeds remain. Allow moisture to drain. Put the seeds on a smooth surface and pat with a towel to remove further moisture. Allow to dry in an airy shady place. Finally store the cleaned dry seed in labelled jars. For some seeds an extra step is to leave them in the water for a few days to allow a bit of fermentation, apparently this helps them to fully ripen, and can improve germination.
Storing seed
I have always thought that I store seeds in a rather haphazard way that could do with improvement. I collect up seed packets, both partially used and homegrown additions, and they tend to accumulate in a cardboard box in a spare room. At least I don’t put them in steamy or damp places such as the kitchen or bathroom! Mostly I use brown or white paper bags for storing bulky seed, adding a label of species name, location source and date. So far I have never managed to sort out longer-term colder alternatives for storage that would probably be an improvement – such as an outdoor shed or even the freezer. As a step towards better storage I have started collecting small dark glass jars (it is handy that I have thing for Marmite) and this year I will be trying them out for storing cleaned seed. Any improvements in storage along these lines should help increase the percentage of germination.
Seed dormancy
Some tree seeds need to be sown straight away as they rapidly deteriorate in storage and these include oak and willow. Otherwise, so long as seeds are well-dried then they have a good chance of being viable. However, if not sowed when fresh, many tree and shrub seeds that are stored will need some further pre-treatment to get going. Often this is a period of cold stratification in moist sand in the refrigerator lasting from 4 to 12 weeks, depending on the species. Native species seeds can be placed in gritty compost in a pot outdoors over winter to naturally germinate in spring (there is a helpful series of short videos about how to do this at Flora and Forage). If seed coats are hard then extra treatment such as rubbing with sandpaper or a dip in boiling hot water may be needed. No hard and fast rules work for all species and the best place I have found for this detailed information about propagation is the Plants For A Future database.
Harvesting buckthorn seed
I squished the buckthorn berries around in a little water to remove the ripe pulp. This process turned my hands green and produced a glorious purple liquid. I have since discovered the incredible range of dye colours from buckthorn bark and berries, including greens, pinks and yellows. In the UK we have two native hardy buckthorns - the alder buckthorn (Frangula alnus) and the common or purging buckthorn (Rhamnus cathartica). It is worth looking out for them as these small trees have useful properties for wildlfe, especially pollinators, along with being the host species for the fabulous brimstone butterfly, as well as a versatile source of botanical dyes. Both have traditionally been used as laxatives, the bark and the berries having strong purgative action (#healthwarning don’t try this laxative at home without advice from a trained herbal practitioner!). For buckthorns to be seed bearing both male and female trees are needed. Beware though as, despite being great for European wildlife, the buckthorns are noted for spreading invasively in parts of the world such as the USA.
***To celebrate National Tree Week I have 50 packets of common buckthorn seed to give away. If you have a suitable space for common buckthorn then see below for free seed offer while stocks last!***
Harvesting hibiscus seed
In the Southwest UK, the hibiscus (Hibiscus syriacus) can grow in sheltered spots and will produce seeds. The hibiscus originates from Asia and Southern Europe and is a close relative of the mallow plant. It has edible young leaves and flowers, with noticeably soothing effects, ideal for herb tea. The seeds are found in attractive small dried heads on the tips of stems. These seedheads can be crumbled to loosen the seeds which are delightfully crescent-shaped and fringed with hairs. Shaking the seeds around on a plate helps to separate off the husks which can be picked out. They can be sown indoors anytime or in a greenhouse in spring.
More herb seeds to save
Seeds are so powerful and they provide the blueprint for many amazing plant species. I would like to encourage more people to experience the collection and saving of seeds. You can see some more examples of other herb seeds previously gathered and written about in the Medicinal Forest Garden Trust blog 'Discovering Herb Seeds'. Using effective seed saving is a great way to promote the range of species that are suitable for many uses. And it is a lovely way to share plants with friends. Seeds don't require a lot of space to store and can be easy to sprout. So I will keep experimenting with ways to 'shuck' seeds of medicinal plants!
***National Tree Week 25 November to 3rd December celebration! Free seed offer to subscribers of Medicinal Tree Woman - I have 50 packets of common buckthorn (Rhamnus cathartica) seed available - send a stamped addressed envelope to me at the address below labelled 'BUCKTHORN SEED' and I can send you 10 seeds while stocks last!***