Graft hybrid attempt

Graft hybrids are a topic of much controversy, has been studied only briefly, and at this point in time the concept is very poorly understood.

For years it was believed that DNA did not cross the graft union further than a few adjoining cells, then it became clear that metabolites and some DNA could cross the graft union but there was controversy over how far this would travel or if any changes could be inherited by seeds.  Then it started to look as though DNA transfer can be heritable and passed on through seeds to some extent.

While there is still a lot of controversy over this topic, it is now pretty clear that DNA can cross the graft union under some situations and may cause heritable changes to be incorporated into seeds.

Graft hybridisation is not the same as cross pollinating where half of the DNA from each parent is passed on.  We are not sure how much DNA from each parent is passed on, and it appears in many cases that 0% is passed on.  At the moment there are more questions than there are answers.  I find it fascinating.

Cross pollinating strawberry and raspberry to create a hybrid has a low rate of success and is rather time consuming.  I can see why so few people have ever attempted this.  Around two years ago I made a large number of attempts, planted large numbers of seed, and only have a very small number of fruiting intergeneric hybrid plants to show for my efforts.

Given that heritable changes to DNA can sometimes be incorporated through grafting, it got me thinking.  Perhaps it is possible to use graft hybridisation to cross strawberry and raspberry plants?  Perhaps I graft the two, allow the scion to flower/fruit, collect the seeds, if I plant the seeds they may display some form of genetic cross over between the two plants.

To attempt this, the first question is one of what part to graft.  It may be possible to graft the growing tip of a raspberry onto strawberry roots, I am self-taught at grafting and that sounds difficult.  I worry that I am not up to this kind of grafting and would likely just kill both plants.  So this may not make crossing the two any faster or easier than simply cross pollinating a lot of flowers.

Or, would it be best to graft strawberry scion onto a raspberry plant?  Some strawberry plants can go from seed to fruit in 5 months or less, saving and germinating strawberry seeds is simple.  I guess it is possible to excise the strawberry’s growing bud and graft that to a raspberry somehow, again this sounds like a difficult graft for someone with few grafting skills, so I would probably end up killing both plants.

Assuming that it is even possible to graft a rasberry and a strawberry, this graft may or may not take all that easily as there may be issues with mild incompatibility.  I am self-taught, and don’t have a laboratory, so will be working in the field where insects and birds and children frequently visit and the weather can be downright hostile at times.  If I have any hope of succeeding I need to work with something that is simple to graft to increase my chances of success.

Strawberry runners grafted onto a raspberry cane

I decided to try and graft strawberry runners onto a raspberry cane.  Runners give me a large area to work with so if I mess up I can cut off that part and try again, I can do this several times if needed, until I make a neat cut on just the right angle.  You can't really see in the photos, but some runners are long and others are short, this was partly to see if that made a difference and partly because I had to cut some runners shorter as I made the cut wrong a few times.  I did this with a few plants but only took pictures of the first one.

With runners the young plantlet is still developing, if grafted onto a more mature raspberry cane it will be a kind of ‘mentor graft’ which is said to facilitate DNA exchange.  Given the length of a raspberry cane I can graft large numbers of runners and increase the chances of one working. I ended up grafting more than is in the photographs, about half a dozen runners per raspberry cane.  I wanted to do more but ran out of time and effort.

I grafted several strawberry runners onto a few raspberry plants.  I am unsure if ploidy makes any difference to success rates of grafting two different genus so I used both diploid plants (2n = 2x = 14).  The runners were very thin and difficult to use, but it was all I had available at the time.

To the best of my knowledge, no one has ever attempted anything like this using strawberry and raspberry.  There have been a few attempts using various Solanaceae species that have confirmed genetic material can cross the graft union and these changes can be heritable in the seeds, and at least one intriguing graft hybrid experiment using plums, but nothing with Rubus and Fragaria.

My plan was to graft strawberry runners onto raspberry canes, then when the strawberry plant was large enough I would allow it to root in soil.  Potentially some raspberry genes may have crossed into that strawberry and may be heritable.  I would then allow that strawberry (which had previously been grafted onto a raspberry) to flower and set fruit, I would collect and plant seed, and then see if there were any noticeable difference in those seedlings.

I assumed that if this worked there would be a low rate of genetic cross over, so I was planning on growing out a lot of seedlings.

I ran out of time on grafting day and kept some of the runners not grafted but sitting in a glass of water.  They all died after a day, so gave me hope that my poor technique grafting may have been successful.  All of my grafts looked bad for a day or two, then they perked up.  This was a very encouraging sign.

After 8 days there was a preventable mishap.  One hot day most of my strawberry raspberry grafts died.  The plants were in a plastic bag to increase humidity, but it also made a little solar oven which cooked them.  They looked fine in the morning, and were crispy and dead in the evening.  I think it was due to the heat rather than incompatibility issues as the raspberry hosts dropped a lot of their leaves that day.

After that incident I had one single grafted runner that was still alive and growing well.  It was small but growing fast, so I assumed the graft had taken.  This runner had a small plant that then sent out a further runner, so I was confident this had worked.  This grafted runner remained alive for 28 days after the initial heatwave and was developing well, I put a pot of soil under it so it could send down roots, then another heatwave hit and it died before it had a chance to root.

My little strawberry runner survived for 36 days after I had grafted it and had a nice looking little plant ready to set down roots.  This was extremely frustrating.  The rest of summer was record breakingly hot so I didn't try again.  I even lost a lot of my raspberry plants that were growing in the garden.

I hope to give this another try in spring if I have time.  The fact that the last runner lived so long was encouraging, but at this point I don't know if this could work, let alone if my grafting skills are good enough to succeed.  Unfortunately either no one has tried this before, or they haven't bothered making their results accessible, so I will have to do it and learn for myself. 

If I give this another try I plan to write a blog post of the results.  Even if I am unsuccessful it is a good result and worth learning from.  I wish someone else had tried this properly and either failed or succeeded, that way I wouldn't have to start from scratch.  Let's be honest, if this is not going to work then I am just wasting time.

Helsing Junction Blue tomato

For a few years now (ever since they mysteriously made their way into the country) I have been growing different varieties of high anthocyanin tomatoes.

High anthocyanin tomatoes turn dark blue to black where the sun hits them. Unlike the old heirloom varieties that were called black but were really a muddy brown, high anthocyanin tomatoes actually can be black.

Anthocyanins are a group of powerful antioxidants, darker varieties contain higher concentrations of these antioxidants so are presumably even healthier to eat than regular tomatoes. The early high anthocyanin lines such as ‘OSU blue’ were incredibly black, but didn’t taste all that amazing. Sadly they didn’t taste all that much better than store bought tomatoes.

These early released black varieties have been used in breeding efforts to create tomatoes that are black and also taste good, huge improvements have been made in this area and some of the more recent released high anthocyanin varieties are starting to taste pretty good.

Helsing Junction Blue tomato - not ripe yet

I have been growing a tomato called Helsing Junction Blue (or Helsing Junction Blues, I am unclear if it has an ‘s’ on the end). This variety is said to be bred by Tom Wagner and named after the Helsing Junction Farm in the Chahalis River Valley, Washington state. Normally I am not a fan of Tom Wagner’s tomatoes (other than a tomato named Verde Claro, which is truly exceptional), and normally I am not a huge fan of high anthocyanin tomatoes (although many of the newer varieties are actually really good), but this one yields well and tastes great.

Helsing Junction Blue grows into a tall and vigorous plant with regular leaf. It is an indeterminate variety, meaning it will fruit all season long until killed by frost, or can be grown as a perennial if protected from frosts. Being tall means they will need some form of staking or they will sprawl and cover a lot of space. Like many indeterminate varieties it is incredibly simple to grow from cuttings.

For me Helsing Junction Blue produces high yields of large cherry tomatoes over a long season, they are sweet and have a decent rich taste for a black tomato.

Early in the season this variety looks like any other, you can tell it is high anthocyanin as the stems get a purple tinge to them at times. Its flowers and unripe green fruit are round and look unremarkable.

Before the fruits ripen they start to turn purple, bright purple, it is almost unbelievable the purple they turn. I really wish they stayed this colour when they were ripe, but they don’t.

Helsing Junction Blue unripe fruits

Not ripe, but they look great!

Eventually they start to ripen, places the sun does not hit turn red, and anywhere that is hit by the sun turns black with red underneath. Higher exposure to ultraviolet light makes them darker, and strangely enough cool temperatures combined with high light intensity enhances the dark colouration.

This means that fruit produced in autumn is noticeably darker than fruit produced at the height of summer. It is only the skin that is black, inside the flesh of this variety is red.

Helsing Junction Blue - ripe fruit

Helsing Junction Blue, they do get much darker black than this

Once they have started to ripen you end up with a large plant covered in fruit from unripe to ripe, ranging from green, to an interesting purple, through to red and black.

I have had people stop and stare at my plants and ask me questions, bewildered that such interesting colours can actually be real. People always want to eat a bright purple ones, I try to explain that purple are not ripe and the black and red ones are ripe. They taste those and like them, but are always a little disappointed that I won’t let them eat the unripe purple ones.

People want to eat the purple ones, but they aren't ripe yet

Helsing Junction Blue tomatoes have a nice, reasonably rich taste, and are pleasantly sweet. I have never cooked with them by themselves so can’t comment on that. We have frozen them in with other tomatoes and cooked with them all mixed together, the results vary but the number and composition of varieties of tomatoes included in these frozen packs also varies considerably.

Being a cherry tomato means they are often eaten whole and are good used in salads. My kids happily pick them and eat them from the plant whenever they walk past the plants and I am not watching. Yeah, they think they are being sneaky but I know they do this, I just don’t try to stop them because they know not to pick the ones with string that were used for breeding and/or isolated for seed saving.

I recorded Helsing Junction Blue as taking 166 days from planting the seed until picking the first ripe fruit (this is often referred to as 60 to 70 days by most seed sellers, but they don't start counting until transplant).

Towards the end of the season when the weather cools the fruits looks its darkest, and the stems take on more purple colouration. No tomato tastes its best when ripened in cool weather (or if ripened in warm weather but then put in the fridge for a few hours – seriously why do people ever do that), and Helsing Junction Blue is no exception. I have never been overly impressed with the taste of any variety of tomato that ripened when the weather was cold.

Some of my plants flower through light frosts, then they start to produce flowers and fruit that are odd. I don’t know how to explain, some fruit are almost like they are inside out. Some of the flowers look like they produce fruit before the flowers open and had no chance to produce pollen.

I don’t know if they are parthenocarpic and set fruit without pollination or if something else is happening here. I have never had these weird fruit ripen as heavier frosts kills them off first, so I don’t know what they will look like or taste like or if these late fruits contain any seed. I assume these oddities are caused by the cold temperatures, perhaps it is a trait from one of the wild species that was used to breed in the dark colour.

Fruits forming before the flowers even opened

Anthocyanin concentrating in the leaf tips during high UV and low temperatures

Weird fruits forming before the flowers opened

Based on their taste, yield, resistance to disease, and impressive looking fruit I am pretty happy with Helsing Junction Blue tomatoes. I don’t grow them each year as I have far more varieties than I can fit in the garden in any given year, but they are in my rotation to be grown every two or three years.

 I sell seeds of several varieties of tomato as wel as a bunch of other perennial vegetables and herbs on my for sale page.

Comparing yield of female asparagus and male asparagus plants

Asparagus (Asparagus officinalis) is a perennial vegetable that is dioecious, meaning that individual asparagus plants are either male or female (or sometimes they are 'super male', but that is a topic for another day). There aren't a huge number of dioecios vegetables, which makes asparagus interesting.

With asparagus you want many long and fat dense spears that are not fibrous, when they start to become thinner you stop harvesting for the year. It is common advice to remove/kill all female plants as the males are said to provide larger yields of fatter, longer, and better quality spears. It is common advice that female asparagus produce thin spears so can be weeded out early.

But is this really true? I have never met anyone who has tested this theory, have you?

 

I have always wondered if this was true or just another garden myth that people spread about. I used to have heaps of seed grown green asparagus plants scattered through our orchards, some produced fatter or longer spears than others. I never noticed any difference between the males and females.  But these grew from seeds deposited by birds, and were various ages, and none of them were watered or weeded, so you can't really draw any sensible conclusions from that.

I also had a female purple asparagus plant that used to grow the fattest and most succulent spears I have ever seen. Perhaps that is a variety trait and male plants of the same variety would be even better? 

I wanted to do a comparison to see if this is the case, but I lack the necessary resources to run a trial properly. As I could not run this trial to get this information myself I looked up some peer reviewed papers, and the results were really surprising.

Female asparagus producing long fat straight spears

Firstly there were a bunch of papers claiming that certain all male F1 cultivars (or 'male dominated' F1 cultivars) out yield traditional heirloom varieties that have both male and female plants. That is nice, and useful information for commercial production. This wasn't surprising, many F1 vegetable hybrids out yield tastier heirloom varieties. I want to compare the yield and quality of male to female of the same variety, not just comparing one variety to another. I am also interested in quality, not just quantity.

I found a few papers published in 1909 saying that all male asparagus fields provide higher yields than mixed fields. After reading though the methods it sounds like the mixed fields had issues with competition (from seedlings) rather than being a direct comparison between male asparagus and female asparagus plants. Again this is useful for commercial growers, but not all that useful for home growers with small numbers of plants.

Purple asparagus

So I kept looking and I stumbled across a bunch of papers, some published recently and others were far older than I am, and they compared male to female asparagus plants of the same variety to one another. Some papers focused on just one variety, others focused on multiple varieties, and they all had similar trends.

I will provide the full abstract of one of these papers, and then use sentences from others to highlight the findings.

 

Comparison of spear yield and quality between male and female asparagus plants in protected mother fern culture (https://www.ishs.org/ishs-article/1223_24)

"A higher yield of spears is generally obtained from male asparagus plants than females in outdoor culture. However, recently in Japan, it was reported that the spear weight and yield of female plants was generally greater than those of males in rootstock-planting forcing or mother fern culture. 'UC157' plants were grown in large black polyethylene pots. Spears were harvested daily and their weight and external appearance were recorded for four and two years, respectively. Spear numbers were not significantly different between male and female plants in spring, and tended to be greater per male plant than per female plant from summer to autumn. Mean spear weights per female plant were significantly higher than those per male plant in spring and from summer to autumn. Spear yields per female plant were also significantly higher than those per male plant during spring, whereas no significant differences were found from summer to autumn. Spearhead tightness, an important external quality indicator, was significantly better in female plants than males. From these results, we concluded that in spring, the spear yield and quality of female plants would be better than those of male plants without causing a difference in the annual yield. Therefore, a choice of all-male varieties seems to be not necessary and all female cultivation could be profitable for protected mother fern culture in Japan, since the price of spears in spring and heavier spears is higher in the Japanese asparagus market".

 

A large scale experiment which compared male and female asparagus plants from several varieties published in 2016 said: 
"The results of this study show that the female plants had a significantly higher rootstock weight, weight per spear per plant, and weight per early spear per plant, whereas the male plants had a significantly higher total spear number per plant, early spear number per plant, and significantly fewer days to first harvest".

Another paper said: 
“With the average stalk diameter there was no difference between male and female plants in 1964; in the first two years the diameter of the female plants was larger than that of the male”.

Yet another paper stated: 
“Female plants had higher stalks and longer length to primary branch than male plants”.

Another paper states: 
“…highest number of very thick spears appears generally in female plants”.

 

This is all incredibly interesting, it means that female asparagus plants do not necessarily produce fewer spears in spring (when I am harvesting them), or thinner spears, or spears of lower quality than male asparagus plants. 

If anything these papers demonstrate that female asparagus plants often produce fatter, longer, better quality spears while males tend to produce more spears that are shorter, thinner, and of poorer quality.

Female asparagus producing berries

Knowing this, the first thing you do is ask why we have always been told to remove and kill all female asparagus plants.

 

I believe this advice is mostly due to female asparagus’ incompatibility with large scale commercial production, and partly due to the extra work required to look after them for home gardeners long term. 

Male asparagus plants flower and then the flower falls off, female asparagus plants flower and produce little red fruits that are filled with seeds. In time the female asparagus plants drop their fruit, the seeds eventually germinate and the bed gets choked with too many plants, leading to a reduction in quantity and quality of yield. Sometimes birds eat the berries and deposit the seeds in concentrated places causing a bit of a weed issue.

For a commercial grower with acres of asparagus this would be devastating and costly/difficult to overcome. Spraying a pre-emergent herbicide to prevent seedlings from growing sounds like extra time and money being spent, growing only male plants would be better in this situation. 

In a commercial scale, producing many thin spears often results in higher profits than growing fatter, longer, higher quality spears. Remember that people in cities need to eat, and commercial agriculture must focus on profits and feeding landless people. If they didn't we would have massive famines in the city. Commercial agriculture must focus on producing large quantities of food that people can afford, often this is done at the expense of quality.

Commercial asparagus growers tend to want thin spears. I have even seen certain asparagus varieties described as having thick spears, and then recommending planting closer than normal so they will produce thinner spears.

When growing food in the back yard can focus on quality.  Quantity is nice, but when home grown it comes second to producing high quality food.

Asparagus surviving the heat and dry

For a home grower with a small number of plants who is growing for personal consumption rather than profit, this news is not so gloomy. In the long term they either need to remove all the berries, or carefully dig up and transplant the seedlings, otherwise the bed gets choked and only thin spears are produced. On the other hand, as a home grower with few plants it isn’t too hard to pull the berries off and sow them somewhere, providing you with extra asparagus plants to either keep or give away. So this extra work actually becomes a positive. 

According to the literature above, female plants often produce longer, fatter spears of higher quality. These are exactly the traits that I want when growing asparagus!

If you are growing food at home you may as well grow the best. I am not growing asparagus to sell the spears, I am growing to eat them. So if the choice I have to make is either more spears that are thin and low quality, or less spears if they are fatter and of superior quality, I will choose the latter every time.

Asparagus growing between QLD arrowroot

Personally my plants are all seed grown and I just grow whatever. I have a mix of male plants and female plants and I normally remove the berries. 

 

I have grown asparagus from seed, it takes a lot of time and effort so most people prefer to buy dormant crowns. I have been reluctant to sell seed grown asparagus as (unless I grew an "all male" F1 hybrid) a mix of male and female would be produced and I wasn’t sure if the female plants were worth it. I certainly don’t want to sell low quality plants. 

Now that I know more about the quality of female asparagus plants, and why we are told to remove female asparagus plants, I plan to get some seeds of a few heirloom varieties to grow them out and offer year old crowns for sale.  

Keep an eye on my for sale page from next winter and I will try to have a few crowns of heirloom asparagus varieties for sale.

Chilean Guava

For a few years I have been growing a plant with the common name of Chilean guava (Ugni molinae).  I think there has been a push of late to call them "Tazzie Berry" or "Tassie Berry" to make them more marketable while people think they are a new fruit.  According to wikipedia  it is native to Chile and Southern Argentia where the local Spanish name is "murta", and the Mapuche Native American name is "Uñi" or "Uñiberry". 

This is a nice enough looking shrub that grows really nice tasting fruit.  I have read that they were the favorite fruit of England's Queen Victoria.  Perhaps she actually liked them, or perhaps she liked having something that at the time would undoubtedly have been rare and impossible for most people to buy and therefore extremely prestigious, or perhaps a little of each.

I don't think Chilean guava love blazing heat, so I try to grow them in partial shade.  They take frost, but it sometimes damages the new growth, so I try to grow them near a wall where they experience slightly less severe frosts.  Their growth rate is not overly fast and they are evergreen.

Unfortunately I don't think I have quite worked out its preferred growing conditions.  I grow mine in a pot and each year it grows larger and flowers like crazy but I never get huge numbers of ripe fruits.

At the start of the season it is absolutely covered in unopened flowers.  They normally stay like this for so long I begin to wonder if it has flowered but I missed it and they started to turn to berries.  Then they eventually open and I remember that the unopened flowers stay on the shrub for a long time.

Chilean guava unopened flower buds

After what seems like forever, the flowers begin to open.  There are usually hundreds upon hundreds of flowers, almost too many to believe, and they open successively over a very long time.

The flowers are white or light pink and rather pretty.  Oddly enough I have never seen any pollinating insect on them.  I have tried hand pollinating and it has not made a noticeable difference to fruit set.  Over the next few weeks the shrub is incredibly pretty with all of its flowers.

Chilean guava flowers starting to open

Soon enough the petals drop, and each flower begins to turn into a little fruit.  At this stage I look at the many hundreds of fruits and start to expect a massive harvest.  Each branch is loaded down with dozens of tiny unripe fruits.

Chilean guava berries starting to form

Then for some as yet unknown reason, many of the immature fruits begin to abort.  They do this at different stages, some are far more developed than others.  There are literally hundreds of fruits dropping off each day for a few weeks.  I really don't understand why.

If this were due to lack of pollination they should have aborted earlier.  Perhaps the soil isn't right, maybe they need more water, or frost or heat or wind gets them.  Hopefully I work out how to stop this as I would love to pick thousands of these fruit from each small shrub.

Chilean guava covered in unripe fruits

Tiny fruits starting to abort

Eventually a few of the fruits ripen after they reach pea size.  I don't think I have taken any pictures of the ripe fruit as they are usually eaten pretty fast.  It would be nice if there was some commercial grower of these as they taste nice and I am sure there would be a market for them.

I am bad a describing taste.  To me they taste really good, a bit like strawberry crossed with a pine tree.  That sounds dreadful.  Perhaps someone else would be better at describing the taste than I am!  Even though my description is not flattering they really do taste good.  They smell great, similar to some tropical fruit mixed with pine tree.  I really don't think I am doing this justice.

The texture of the flesh is like a firm slightly dry banana.  Again this sounds bad, but it is really very nice.  I don't think I am all that good at describing this kind of thing.  I am better skilled at growing/breeding/eating things than I am at describing them.

The leaves smell like spices when crushed.  I tried eating one once and was not impressed with the taste or the texture as they were very tough.  I grow them for the fruits, and for the flowers, I don't even know if the leaves are toxic so I don't intend to eat the leaves again.

Over the season we sometimes get hail and crazy wind, invariably it breaks of a few small branches.  I try to use these to grow a few new plants.  I am told that Chilean guava is simple to grow from cuttings, for me they sometimes take a few weeks and other times take a few months to grow roots.

If I have any spare cutting grown plants that have strong roots and are actively I sell them through my for sale page.  If you are interested have a look.  I don't take pre-orders because I can't guarantee how long it will take for them to root.