This might not surprise you given my tree obsession, but I’m nostalgic about mulberry trees. If you own one of these or grew up around them, you may have noticed that their juicy fruit, attracts birds, squirrels, and children. But better that they are enjoyed by someone, rather than ending up on your car, or staining the cement! It seems impossible to pick ripe mulberries for jam without turning your fingers red.
I think the character they bring to a yard makes them a great planting choice. But it’s very important to know how quickly they grow, and what height you can expect them to grow to.
On average, mulberry trees grow by one to two feet (30-60cm) per year, and reach a height of 50 feet (15 meters) and spread of 39 feet (12 meters). The black mulberry is the slowest growing, gaining around one foot (30cm) per year and reaching a height and spread of around 10 meters (32 feet).
You’ll notice I’ve singled out the black mulberry, Morus nigra, as the slower-growing. It’s important to be able to tell it apart from the other common mulberry species, those being the American native red mulberry Morus rubra, and the white mulberry Morus alba. The red and white mulberries will both grow at around the same pace and to the same height and spread. In fact the lines between these two species are increasingly blurred because of hybridization between the two, with white mulberries somewhat taking over the red’s turf over successive generations.
I tend to think it’s a lot easier to visualize heights in spreads in terms of what we know. So – a red or white mulberry tree can grow about as tall as a two story house in 10 to 20 years, and by 50 years can grow over twice as tall as one. They eventually spread to the width of about 5 or 6 parking spaces. Bigger than you’d think, for a tree that’s often referred to as a bush! The black mulberry is going to be about two-thirds as big in height and spread, though.
Black mulberry differs from the other species in that it has consistently black fruits and uniformly fuzzy and hairy undersides of its leaves. Red mulberries are slightly fuzzy underneath and have red/dark red fruits, while white mulberries have smooth undersides to their leaves and have fruit that can be white, pink, lilac or even red!
It’s worth mentioning a couple of particularly popular mulberry cultivars that have specific growth habits. The dwarf everbearing mulberry tree is a small version that is often grown in a pot and is popular for its consistent fruiting and small size. It may grow only by a few inches per year, and to only 6 feet (1.8 meters) in height. But planted in a sunny spot with deep, loamy soil it may grow to as tall as 12 feet (3.6 meters) in height and spread.
The weeping white mulberry, Morus alba ‘pendula’, is another interesting and common cultivar that’s enjoyed for its beautiful weeping habit and smaller size that other white mulberries. Again, it grows slowly by the standards of other mulberry trees – about 6 inches (30cm) per year, and to a lower overall height – about 2-4 meters tall.
How long do mulberry trees live?
As a general rule, mulberry trees are said to have a similar lifespan to that of humans – around 75 years on average. However, the white mulberry is believed to have a shorter lifespan on average, usually only surviving for 20-50 years.
Typical to all trees though, there are some notable exceptions. First President of The United States George Washington planted 5 white mulberry saplings at Mt. Vernon in 1795, and as of 2017, one is still alive – that 222 years! How does that work? Check out my article on whether trees die of old age, or can live forever!
Why is my mulberry tree not growing?
For a variety of regions, not all mulberry trees and bushes will grow as quickly as they should, or reach their potential in terms of height and spread. While their fairly robust trees, there are a range of factors that can and will stunt their growth – such as frost, sun levels, soil conditions and certain diseases that afflict mulberries. If your tree isn’t growing at the expected rate (see above) it’s likely one of these will be at play.
Mulberry trees have limits to their cold tolerance. They will grow in regions as cold as USDA hardiness zone 5, which means areas where there is an average annual minimum winter temperature of -20 to -15 °F (-28.9 to -26.1 °C). But they’re more likely to grow well in slightly warmer regions, where frost won’t nip the ends of their new growth.
The black mulberry in particular may struggle down to zone 5, and do better from zone 7 (where the average annual minimum winter temperature is 0 to 5 °F/-17.8 to -15 °C) and upwards.
If you’re in the USA, you can check the USDA hardiness zone here to find out which you’re in.
Mulberry trees are quite tolerant to a range of soil pH levels but they prefer deep, slightly sandy soil which drains well. They’ll often tolerate a bit of flooding for one season, but will struggle if it happens again. They’re known to be able to endure drought better than many other tree species.
For the best growth rate, position them in full sun – they’ll tolerate only light shade, so won’t grow in a very sun-sheltered spot.
The most important disease affecting mulberry tree growth is mulberry bacterial blight, which is caused by Pseudomonas syringae. It causes irregular dark green, brown or black spots on the leaves and fruits. It’s been noted to affect the growth and quality of mature trees. If your mulberry tree leaves show irregular spotting, it’s probably best to consult a trained arborist as soon as you can.
Mulberry trees have a long dormant phase, and can seem slow to pick up growth during the dormant season. A young mulberry can be stimulated by produce new growth some vigorous pruning – see ‘pruning mulberry trees for faster growth’ below.
Why is my mulberry tree not producing fruit?
Mulberries typically don’t produce fruit until they are 8 or 9 years old. Grafted varieties, having the rootstock of a more mature tree, will usually produce fruit much more quickly, often in the first or second season.
But some mulberry trees will never fruit unless they have certain things put right! Whether you are not getting any fruit at all or would like to see more mulberries on your tree, have a look at this page where I’ll explain all.
How to make a mulberry tree grow faster
Pruning mulberry trees for faster growth
Personally, I love the natural shape of the mulberry, especially the black mulberry tree which has a gnarled, aged appearance even when relatively young! But there are some things you do with your secateurs to make sure you have a happy, fast-growing tree.
When your mulberry is a sapling, you’ll want to encourage a ‘central leader’. That means if you have two stems that both appear to be competing to be the main ‘trunk’ of the tree, it’s best to keep the one that’s most strong and vertical and prune off the other. The best time to do this is when the tree is dormant, i.e. in the winter when there are no leaves and no signs of new growth.
If you’re hoping to maximize fruiting rather than upwards growth, there’s another easy pruning method that you can employ – see my post on how to get your mulberry tree to produce more mulberries!
Fertilizing mulberry trees for faster growth
Truth be told, mulberry trees don’t need a lot of fertilizer to grow. But that doesn’t mean that a little time spend fertilizing won’t help your tree put on some healthy growth more quickly.
A bag of good old 10-10-10 fertizer is generally a good way to go for mulberries. I recommend applying twice a year – in mid-winter when the tree is dormant, and in early summer. If you apply too late in the summer, you may stimulate new shoots that will simply get nipped by the coming winter frosts.
10-10-10 fertilizer contains 10 percent nitrogen, 10 percent phosphate and 10 percent potash. These three nutrients are the most important growth factors for most plants. But you can certainly get into more detail if you’re feeling keen and take out the guesswork. It isn’t hard to test your soil for specific nutritional deficiencies using a commercial soil test kit… seriously, more people should do it. If you’re interested, check out Rapitest’s soil testing kit, which will tell you your nutritional components and the pH as well. That’s the one I use.
Mulberry trees expend a lot of their nutrients producing the abundant fruit that they’re known for, so providing adequate fertilization will help ensure you get a better crop of fruits each year as well.
Watering mulberry trees for faster growth
Mulberries are drought-tolerant trees, but they still prefer irrigation during dry spells, especially if you want to see your mulberry maximize its growth potential.
A 10-minute soak once every two weeks is likely to be enough when the weather is hot. Alternatively, you can check soil moisture by pushing your finger one or two inches down into the soil near the base of the tree. If the soil feels dry or doesn’t stick to your finger, give it some H2O. But avoid blasting hard at the base of the tree with your hose.
Mike Dickison, CC BY 4.0 https://creativecommons.org/licenses/by/4.0, via Wikimedia Commons
Glmory, CC0, via Wikimedia Commons
DS28, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
Peter Coles, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
Vincent van Gogh, Public domain, via Wikimedia Commons