A couple of years ago, when I was still attempting to grow a small selection of apple trees in an air-pot mini-orchard in our back garden,1That particular experiment has been called to a halt and two of the three trees have been relocated to the allotment and planted in the ground, where I hope they’ll be much happier, healthier and more productive. The third, a ‘Blenheim Orange’ on MM106 rootstock that was really suffering from being potted up – memo to self, notoriously vigorous cultivar on standard rootstock is not a good pot-tree option – has been donated to Holly Mount Community Orchard, where I hope it will thrive for decades to come. I thought it might be interesting to try to track and observe the development of a single fruit bud, from winter dormancy through to (hopefully) fruiting and harvest the following autumn.
One of the three air-potted trees – a ‘Herefordshire Russet’ – had a well-placed branch that was tipped with a potential fruiting bud that looked like a good prospect2I also picked this tree because, being a russet apple, it was far less likely to be the target of apple-theft by marauding squirrels, who definitely seemed to prefer scrumping from the other two, redder varieties. and so in December 2020 I took the first of the following series of photos3Please n.b. – I’m not a particularly good photographer and lack the equipment to ensure a geo-precise positioning of the camera – or the time to digitally manipulate everything to the same size after the fact – so the pics are what they are.. The results offer a rather fascinating overview of the growth and development pattern of apple fruit buds, on this particular cultivar at least.
There are two sets of photos below. The quick gallery version provides a thumbnail overview of the development of the bud through the year. The detailed version contains commentary and explanation, accompanied by larger images. Scroll on down to that second set if you’d like to see more detail and you don’t mind loading all the full-sized image files.4Maybe not recommended if you’re viewing on a mobile device with a limited data plan.
If you have any questions or observations, please do feel free to get in touch, via the comments, or you can send me an email.
Quick Gallery Version
Click on any thumbnail to enter lightbox mode. You can then scroll through (L/R) to view the gallery images in sequence.
Detailed Version
Winter – Dormancy to Awakening
As winter temperatures remain low, the potential fruit bud at the tip of the branch – which was initiated the previous summer and primed to flower this year – remains dormant, with the delicate blossom inside protected by a tough outer bud casing. As long as the weather provides enough chill hours during this period of dormancy, we can look forward to bud-break and blossom in a few weeks’ time.
In the meantime there’s no apparent change for weeks on end, even as the temperature gradually rises through January and February:
Spring – Rapid Growth and Development
Towards the end of March, dormancy is well and truly broken. The fruit bud shows a first flash of green as leaf-tips begin to emerge:
Leaf development is rapid post-equinox, as springtime light-levels increase. Just below the fruit bud, new leaf buds are starting to break open as well:
Within the tight cluster of new leaves at the tip of the shoot, the tightly furled blossom buds are now visible. The sepals, which at this stage are protecting the delicate blossom petals within, are tinged the faintest pink at their tips:
Disaster almost strikes! Snow in mid-April brings a sudden drop in overnight temperature…
…but apples are made of sterner stuff. If a sharp frost had struck a week or two later then all might indeed have been lost, with blossom too badly damaged, or even killed off, before it could be pollinated. Luckily, the tightly-furled, dark pink petals remain healthy. Below the largest, terminal or ‘king’ bud, several secondary blossom buds can be seen. (As can a few miniature aphids):
It’s nearly the end of April and the blossom is just beginning to unfurl. (The aphids are persistent as well, despite repeated attempts to wash them off):
Three days later, the terminal bud is fully open and the secondaries are well on the way. (The aphids are hanging on, but don’t seem to be doing any real damage to the buds or blossom):
Here’s the air-potted ‘Herefordshire Russet’ tree, to give you an idea of the blossom coverage in April 2021. It looks like the tree is still a few days away from ‘full bloom’5Full bloom is “defined as the date when 80% of the terminal (king) flowers on spurs are open.” (Foster et al, 2003) at this stage. Our subject blossom cluster is the unfurled one at the bottom-right of the tree:
It’s May Day 2021 and our blossom cluster is looking suitably festive:
There are a total of six blossom flowers in the cluster. The terminal blossom was the first to open and the five secondaries are opening in sequence shortly afterwards:6A staggered opening increases the chances of later blossoms surviving if a late frost or some other cause damages the earlier ones.
According to the weather records for May 2021 we had a sharp frost for a couple of nights at the start of the month. That explains the browning and damage to the tips and edges of some of the blossom that becomes apparent over the next few days:
Continued deterioration of the apple’s flowers heralds the imminent end of blossom season for another year:
The ‘Herefordshire Russet’ tree is now just past the full bloom stage:
A few days later and the petals on our subject bud cluster have all fallen. Now is the moment of truth. Have the pollinators done their work, or did that sharp frost kill the blossom before successful pollination occurred?
A few days pass, but it’s still too early to say for sure:
A week later and… success! There’s a distinct change to the fruiting structures: note the brighter red colouring of the ovaries at the base of the stigma.7The ovaries are where the apple’s seed are stored, and the stigma is the part of the flower that contains the female organs, as opposed to the stamen, which contains the pollen-bearing male organs And the hypanthium8The hypanthium is the cup-shaped part of the flower, at the end of the pedicel, that holds the anthers and the stamen; the flower’s male and female (respectively) reproductive organs. – that develops into the ‘fleshy’ part of the apple; the part we actually eat – has just begun to swell:
Eleven days later and four miniature fruitlets are forming, two fewer than the original six buds in the cluster. The terminal fruitlet is the largest and the secondaries are just a little bit smaller. The missing two weren’t fully pollinated and so have dropped away:
On June 13th I took the decision to thin out the fruitlets in the subject cluster – and across the rest of the tree – to leave just the dominant, terminal fruitlet. This was done to improve the chances of that one fruitlet developing into a good-sized apple, without any competition for resources from the secondary fruitlets.9It was a bit of a gamble, because if something happened to that fruitlet then this photo series was finished for the year, but keeping more fruitlets on the cluster would have weakened them all, leading to smaller fruit and a greater chance of none of them reaching maturity and ripening.
The fertilised ovaries, in which the apple’s five seeds, or ‘pips’, will develop, is now encased in the growing hypanthium, which will continue to swell and eventually ripen, to become a deliciously edible apple fruit:
Summer – Full Steam Ahead
Towards the end of June, not long after the summer solstice, our subject fruit is continuing to develop into a nice-looking apple:10Note that another fruitlet, that was growing on the next branch along, has disappeared. Maybe it failed and dropped, or was knocked off by a passing squirrel or blackbird?
Another three weeks pass and the fruit has lost its red colouring and is starting to develop the light russeting across its golden-green skin that characterises the ‘Herefordshire Russet:
Fruitlets are developing into full-sized apples throughout the ‘Herefordshire Russet’ tree:
Comparing the number of remaining apples to the number of blossom clusters visible earlier – bearing in mind that each cluster would have originally contained up to six fruitlets – indicates just how much thinning was carried out earlier in the month.
As the heat of summer strengthens in August, our subject apple continues to grow and develop very nicely indeed:
As you can see from the next photo, our apple, second from right, and its near neighbours are starting to reach a decent(ish) size. And in the background, you can see a red-green ‘Cornish Aromatic’ from a neighbouring tree:11Sadly, the apples on the ‘Cornish Aromatic’ tree were all destined to become squirrel-lunch before they reached a size and/or ripeness that made them worth harvesting.
At this point the weight of the growing fruit is just beginning to bend the pedicel – the short ‘stem’ that connects the apple fruit to the tree – downwards:
As late summer days gradually shorten, but temperatures remain relatively high, our apple continues to gently swell and ripen:
Autumn – Mellow Fruitfulness
September 2021 was a mild month and our apple continued to ripen in the autumn sunshine. A few heat- and/or insect-damaged leaves – no longer much use for photosynthesis and so a drain on the tree’s resources – drop off (or are removed):
The weather continues to be mild in October 2021, albeit with a little more rain, and our apple hangs on in there:
November 2021 brings a lot more rain, and the loss of the last few of our apple’s nearby leaves:
Then, on the 13th, I come out into the garden with my camera and find this:
Our apple has dropped, most likely because it had reached its full ripeness and the pedicel has naturally abscised – detached from the branch – or a squirrel has made a grab for it and knocked it flying.
(I’m happy to report that the fruit wasn’t too badly bruised, and it tasted absolutely delicious.)
A couple of weeks later and the branch is fully dormant once more:
Comparing photos from the periods of dormancy at the beginning and end of the year, you can see how the branch has changed, subtly but clearly, over the course of the year:
For a start, the branch is now a little thicker, having generated additional woody tissue to strengthen its structure and support the weight of its fruit. The original fruiting bud at the tip of the branch has developed into a ‘bourse’ shoot – as has the bud on the side-shoot in the background – which bears the abscission marks – the scars left behind when a fruit pedicel is detached from the bourse shoot – of not just that one fully developed apple (at the very tip) but also (just below that) the fruitlets that were removed during the thinning process, back in June:
This ‘bourse’ shoot is likely to be the source of more fruit buds in years to come, and indeed, we can see a new potential fruit bud has already formed,12This bud may well have blossomed and fruited in 2022, but I’m afraid I was a bit busy with full-time work, and didn’t think to check… along with two more buds just below it that are likely to produce clusters of leaves.
The year has come full circle and the tree is dormant once again. We orchardists now cross our fingers, hoping for a good, cold winter to prime next year’s fruit buds, and eagerly await the re-awakening of leaf and blossom the following spring.
I do hope you’ve enjoyed this look at the lifecycle of an apple from dormant bud to harvested fruit and have found in interesting. If so, or if you have any questions, or observations to make, please do feel free to leave a comment below. And if you wouldn’t mind taking a moment to share this article on your social media channel of choice, that would be very much appreciated, thank you.
Footnotes
- 1That particular experiment has been called to a halt and two of the three trees have been relocated to the allotment and planted in the ground, where I hope they’ll be much happier, healthier and more productive. The third, a ‘Blenheim Orange’ on MM106 rootstock that was really suffering from being potted up – memo to self, notoriously vigorous cultivar on standard rootstock is not a good pot-tree option – has been donated to Holly Mount Community Orchard, where I hope it will thrive for decades to come.
- 2I also picked this tree because, being a russet apple, it was far less likely to be the target of apple-theft by marauding squirrels, who definitely seemed to prefer scrumping from the other two, redder varieties.
- 3Please n.b. – I’m not a particularly good photographer and lack the equipment to ensure a geo-precise positioning of the camera – or the time to digitally manipulate everything to the same size after the fact – so the pics are what they are.
- 4Maybe not recommended if you’re viewing on a mobile device with a limited data plan.
- 5Full bloom is “defined as the date when 80% of the terminal (king) flowers on spurs are open.” (Foster et al, 2003)
- 6A staggered opening increases the chances of later blossoms surviving if a late frost or some other cause damages the earlier ones.
- 7The ovaries are where the apple’s seed are stored, and the stigma is the part of the flower that contains the female organs, as opposed to the stamen, which contains the pollen-bearing male organs
- 8The hypanthium is the cup-shaped part of the flower, at the end of the pedicel, that holds the anthers and the stamen; the flower’s male and female (respectively) reproductive organs.
- 9It was a bit of a gamble, because if something happened to that fruitlet then this photo series was finished for the year, but keeping more fruitlets on the cluster would have weakened them all, leading to smaller fruit and a greater chance of none of them reaching maturity and ripening.
- 10Note that another fruitlet, that was growing on the next branch along, has disappeared. Maybe it failed and dropped, or was knocked off by a passing squirrel or blackbird?
- 11Sadly, the apples on the ‘Cornish Aromatic’ tree were all destined to become squirrel-lunch before they reached a size and/or ripeness that made them worth harvesting.
- 12This bud may well have blossomed and fruited in 2022, but I’m afraid I was a bit busy with full-time work, and didn’t think to check…
Very interesting and informative, I will attempt to do the same sort of thing on my newly planted apples and plum tree as a reference over the next few years.
Many thanks for your effort.
Thank you Robert, much appreciated.
Hi, Darren ~ I live in the northern lower peninsula of Michigan, not far from Lake Michigan, which tempers our weather quite a bit compared to living inland.
I have six 4th-year apple trees, 2 of which (the Empires) blossomed for the first time this year. The 2 Cortlands had just a couple of blossoms each and the 2 Honey Crisp have had no blossoms yet.
My question is two-fold: Is it unusual for 4th-year semi-dwarf trees to not have blossoms?
And how do we determine whether the branches of the Empires are strong enough to bear fruit? Or should we nip the fruitlets and give the tree more time? In other words, how thick does a branch need to be to support fruit?
Thank you so much ~ Camille
Hi Camille – Well, blossom rates in apple trees are determined by a wide variety of factors, so it can be tricky to pin down an exact cause for low blossom in a particular year. I’d say a four year old tree – depending on how it has been pruned so far – should be capable of producing a fair amount of blossom, but this will depend on all sorts of external influences, particularly the fertility of the ground in which they’re growing, the moisture available to the tree, the light levels that the leaves are exposed to, and any pests or diseases that might be affecting it.
Weather is another major factor in determining blossom set. Apples need a certain number of chill hours over the winter – which I wrote about here: https://orchardnotes.com/2021/01/10/what-are-chill-hours-and-why-do-they-matter/ – for blossom buds to break in the spring, but the temperature has to be within the right range, so too cold can be as bad as too warm. And then the weather at bloom time is vital as well – a mild spell followed by a sharp frost can kill off young buds just as they’re about to open.
The tree’s performance last year also has an effect. If a tree puts out a lot of blossom and develops a lot of fruit one year, if won’t have enough energy to initiate fruit buds for next year. I wrote about this sort of thing in more detail here: https://orchardnotes.com/2021/07/03/far-fewer-apples-and-pears-than-last-year-perfectly-normal/
That last one might not be so important in the case of four year old trees – I guess they didn’t produce a lot of fruit last year? – but that too could be a factor. Depending on the combination of variety and rootstock, different types will reach flowering maturity at different times.
All in all, whilst it’s always disappointing when trees don’t produce blossom and fruit I’d say don’t worry too much. Make sure the trees are well watered in any dry spells this year, and give them a good mulch of organic matter – composted bark is my own go-to – around the base, about three or four feet out from the trunk. And maybe try to avoid doing any summer pruning this year, except to deal with broken branches etc. Leaving as much leaf on the tree into autumn can be beneficial. Research has shown that it allows the tree to store more nitrogen in its roots over winter, which can result in stronger bud break the following spring. Fingers crossed for a blossom-filled 2024.
As for the Empire apples, I’d highly recommend thinning out excess fruitlets to reduce the load across the tree, whatever the branch size. I’ve written about the benefits and method here: https://orchardnotes.com/2020/06/17/thinning-out-apple-and-pear-fruitlets/ so I won’t go into the detail, except to say that it’s definitely the best way to reduce the risk of branch-break, and you’ll get better quality apples as a result as well.