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LifestyleTranscript
00:00so today we're going to be talking about black spot in roses and what we can do to avoid it
00:07i personally grow over 500 different rose varieties in this garden so i have a lot of experience with
00:16trying to contain black spot and also trying to avoid it of course so let's go over some examples
00:24of what we can do to avoid black spot on our lovely roses here black spot also known as diplocarbon
00:35rosera is a fungal disease that spreads by spores the disease is very active in high humidity and
00:43also in high heat and the reason we want to avoid it is of course because it destroys the plant's
00:51ability to produce photosynthesis and a lot of other things the disease is very characteristic
00:58because it has these very very large dark blemishes now the reason why these happen is because after
01:06the black spot spores the fungal spores have penetrated the cell wall they will start releasing enzymes and
01:13these enzymes create necrosis they create cell death and they start using the nutrients and the energy
01:23of those rose cells for themselves to propagate and also to stay alive and release new spores
01:33so and they can infect the stems also not just the leaves but they're less crucial to move on the
01:40stems
01:41than the leaves now if we find a leaf with black spot we will want to snap that leaf off
01:47we'll come
01:48in and look for the base here and then we will pull downwards gently pull downwards and the leaf will
01:55break clean off and that is if you spot a leaf with black spot this one doesn't have black spot
02:00it is
02:01too early in the season for black spot to be present but if it had that's how we do it
02:06and every 14
02:07days you also want to come in and spray with some sulfur spray or whatever chemical you have and every
02:1514 days it forms a protective layer that keeps the black spot away and that's a general method for keeping
02:23your roses clean of black spot but i'm not completely satisfied with this answer because it is the short
02:30answer so let's get to the long answer on how to keep your roses black spot free now the disease
02:39shouldn't be confused with rose rust this is essentially these orange little dots especially
02:46under your leaves they're kind of raised and they're very easy to spot but they don't get as large as
02:53black spot right and it should also not be confused with something like powdery mildew which is essentially
02:59like this silver kind of shine to it kind of like someone put flower on top of the leaves of
03:06your roses
03:08now the first thing we want to be really careful about is if we have any branches from last year
03:13lying about because those branches or leaves might have black spot spores on them so you always want
03:21to make sure you remove those from your flower beds simply to kind of make a quarantine zone so you
03:28kind
03:28avoid it when your roses start leafing up again you don't want those spores to spread
03:35um in general either burn these or get rid of them you don't want to keep them in the garden
03:41as i said they can carry the spores and the spores can splash from the ground up till the leaves
03:46of
03:47your roses and they can reinfect your roses so get rid of old materials so just have a quick look
03:55around
03:55your garden and see if you can spot any old material lying around and see if there's anything you need
04:04to cut off or any dead branches or anything lying on the ground that shouldn't be i could for example
04:12spot a little bit here so i'm going to get rid of that now the first crucial thing we need
04:19to talk about
04:20is watering and this is absolutely crucial when it comes to something like black spot in your roses
04:28we really want to take care of watering but let's go over it so why does a lack of water
04:35lead to black
04:37spot well when our roses like water they enter into survival mode they start releasing a compound called
04:46apa and apa essentially turns off the stomata and that leads to less water reaching the extremities
04:54and it also lowers a lot of the good stuff we want in our roses it lowers phenolic compounds which
05:03are
05:03responsible for our roses immune system it lowers growth hormones like auxins that are responsible for
05:12something like uh flower development and a lot of other good things and it lowers another um compound
05:21called cytokine that's also responsible for a lot of things from rooting and a lot of other stuff right
05:28but the key point here is the phenolic compound right because that is really what lowers our secondary
05:37immune response to something like black spot so remember that lack of water at least more apa at least
05:44to closing of the stomata leads to us having less of these essentially white blood cells if we're talking in
05:54human terms right but um let's go over the next one down here the next one is low nutrient absorption
06:04believe it or not roses need water to absorb the nutrients and i'm going to show it to you
06:11in an example here so let's go to the example
06:16now as you guys can see here we have our regular normal npk fertilizer these white pellets
06:25and it is of course nitrogen phosphorus potassium but look what happens when i put water into the mix
06:33and give it a bit of a stir right
06:38they start disappearing and why is that well all the nutrients our roses need first need to be
06:48dissolved into water before the rose can carry it into the plant into its cell walls right so without
06:58water we are also lagging all our nutrients because there's nothing to dissolve them and carry them
07:04into a rose i hope this makes sense to you guys why water is also a really important function for
07:11transporting what our roses need but not only that all that good stuff that are that's in here that's
07:19been dissolved now if our roses don't get that their immune system gets even weaker and that will make
07:26them even more susceptible to something like black spot
07:32now let's go the last one i'll mention when it comes to water and that is the wax layer all
07:40rose
07:40leaves have a wax layer and that wax layer protects it from a lot of stuff it protects it from
07:47mechanical
07:48damage something rubbing against the rose but it also makes it so it is harder for the black spot spores
07:55to attach to attach to the rose leaf that's why you see a lot of german and danish roses they
08:01have
08:02very shiny leaves because you want a very disease resistant rose but when we lack water that also means
08:11that this wax layer can easily get damaged right and also that not as much wax is produced and this
08:19is
08:20another factor that leads to the point that it is much easier for black spot to invade our roses so
08:28as
08:28you guys can see water or lack of water leads to us having less immune system leads to us having
08:35less
08:35nutrients which again means less growth less flowers less immune system and then the final one is no wax
08:43layer no outer protection either so as you guys can see it is a cascade it is a total catastrophe
08:51and that
08:52is why water is so important for your roses when it comes to avoiding black spot now the second crucial
09:00thing we need to talk about is something called fertilizer so let's go ahead and talk about fertilizer here
09:08so the next thing we will focus on is fertilizer and there's a few rules here the first one is
09:16you
09:16don't want to overdo nitrogen and the reason for that is when your roses grow too fast for example if
09:24you
09:25give them too much nitrogen like lawn fertilizer what ends up happening is that the new growth is very very
09:33soft and pliable and there's a lot of it so what is the issue well the soft growth doesn't have
09:41the
09:42strong cell walls to protect against black spot but another issue is also that this fast the growth
09:50fueled by nitrogen is often so fast that the plant doesn't have the time to develop the immune system
09:58in those parts of the plant simply put the primary metabolism can't keep up with the secondary
10:08metabolism of the plant and if you don't know what i'm talking about i've made a whole video about that
10:14called the primary versus secondary metabolism but for now just trust me you don't want to be over
10:21fueling nitrogen if you have a black spot problem another reason for that is also we need a lot of
10:28potassium and potassium allows the plant to better handle stress it allows it to better uptake water
10:35it allows it to make stiffer cell walls it allows it to better produce its immune system so when it
10:45comes to healthy plants potassium is really what we are after but again you don't want to go extreme
10:52with potassium because if you go extreme with potassium you can pause your plants so a healthy
10:59balanced ratio for most of the year will look something like 10 to 10 10 5 10 and you can
11:06manipulate
11:07that in your own ratios as much as you want if you prefer 515 you can do that right or
11:14414 or something
11:18and down here we have calcium the reason calcium is important is kind of the same reason that
11:25something like potassium is important calcium produces a compound called pectin and pectin helps
11:31our roses strengthen the cell walls which again helps keep out those diseases like fungal spores because
11:39they have to get through the cell wall and both potassium and calcium does that so calcium extremely
11:48important and again when it comes to fighting off black spot right so remember that you want potassium
11:56you want calcium and you want balanced nitrogen not overdone nitrogen because this is absolutely what can
12:03make your roses susceptible to black spot if you've gone too far on the nitrogen right so that was our
12:12fertilizer and if you want some quick numbers to remember i would say aim for about five to six grams
12:19of
12:19nitrogen per month in active growth right and aim for about five to six grams of potassium per month in
12:26active growth and calcium i would say about two to four grams you can do one gram if you're more
12:32cautious
12:32so i hope that settles fertilizer
12:45so the last thing we're going to touch on is the sun our roses need six hours of direct sunlight
12:53some
12:54roses you can get away with four hours but in general aim for six hours and the reason we want
13:02sunlight for roses is because it helps it produce carbon it helps it produce sugar and just like we
13:10humans need energy to be able to fight off disease well roses are the same the carbon and the sugars
13:19and
13:19all that good stuff the roses produces by the sun is exactly what the rose can use to invest into
13:26it is
13:27it's immune system to fight off black spot but there's also another reason we want sun when it comes to
13:34black spot we actually both want sun and wind and that is to dry out the leaves of the plant
13:41quicker you see
13:43black spot needs around seven to eight hours seven to eight hours right
13:52black spot when it sits on the leaves black spot is essentially spores and when they sit on the leaves
13:58they need about seven to eight hours of wet leaves to germinate for the spores to penetrate the cell wall
14:05of course that depends on how difficult we have made the job right with our other techniques but in
14:12general they need wet leaves for a prolonged period before they can penetrate the cell wall and one way
14:20we make that tougher is by having the sun and having the wind around our plants and also making
14:27sure we go in and thin out our roses right so there's more air circulation that way they don't get
14:34as good of a chance of getting these seven to eight hours for black spot spores to germinate right
14:42so that is why the sun is important is important for energy to fuel our immune system
14:48and it is also important to avoid the black spot spores germinating what we don't want however
14:55is we don't want so strong sun that is that stressing our plants right we don't want that scorching desert
15:03heat if we can avoid it and if we do have it we want to up our water intake to
15:09avoid stressed plants
15:11right i hope this all makes sense guys let's continue just we want to try to get the leaves not
15:18wet
15:19when we're watering because if you get the leaves wet there's more likelihood of black spot developing
15:25because a black spot needs wet leaves you also want to try to water early in the morning because
15:32there'll be more time for the leaves to dry out if you have watered them by accident and also to
15:39avoid the strong midday sun that can really scorch the leaves if they're hit by it when they're wet and
15:46you want to try and do a deep waterings as much as possible because roses really like that
15:52you have to remember roses have very deep roots and the water needs to go down there not at surface
15:57level
15:57surface level like azaleas and rodentons so these are kind of the key rules to remember when you're
16:05watering your roses there are a few things you want to be mindful of the closer you place a rose
16:11to the wall
16:13the less air circulation it will get and therefore the more likelihood of developing black spot so do
16:20remember that walls always increase the likelihood of black spots simply because they block airflow from
16:27flowing through it flowing through the rose our goal should always be to thin our roses out a little bit
16:34in the middle so we can make a fist in the center of it and also to make sure there's
16:40a few centimeters
16:41of spacing between each stem so air can get through now another thing you could do is you could do
16:50bark chips or mulch and because that prevents the rain water from splashing directly down to the soil and
16:58up to the leaves of your roses and the reason that can be an issue is because you have the
17:04spores in the
17:05soil and when this splashes directly up on the rose leaf that can carry the spores and when you add
17:13wood or these chips to it that kind of adds an extra layer and it is less likely to happen
17:21and it also retains moisture a little bit better but of course you have the issue during winter time
17:30that it can accumulate too much moisture in the soil underneath the wood chips
17:36so just be aware of that but it can help a little bit with black spot simply because it adds
17:41an extra
17:42layer in general we want to keep an eye out on what roses start the black spot and becomes an
17:48issue
17:48i know louis or deer i have in this obelisk here and gets black spot very early another one is
17:55gertrude jackal you also have great western and a few are of the historic roses but when you notice
18:01which one starts the black spot issue you can kind of decide if you want to isolate them more from
18:07all
18:07plants or if you want to get rid of them for next season so keep an eye on the unhealthy
18:13plants and the
18:14same goes for all your roses keep an eye out for who starts the rust issue for who starts the
18:20black
18:20spot issue because quickly they will spread that to the surrounding plants and they will also get it
18:26because remember it is fungal spores right it is fungal spores so it can quickly spread one thing i
18:33like to do is going around and noticing which gets diseased first because those might be prime candidates
18:46for planting close to companion plants like these salarias or even putting up against the wall right
18:54and because we want the healthy varieties to be the ones that are where there's the least air
19:00circulation because they can clearly handle the disease pressure right and so just keep that in mind
19:07and finally not every rose is going to turn healthy and that is just the way it is sometimes you
19:15just get a bad rose and it is no fault of your own it happens sometimes you can get a
19:21weak specimen of
19:23a rose and even of a healthy variety right i see that all the time when i buy three of
19:29one rose
19:30one of them might like a little bit behind the others right that's completely completely normal
19:36now remember roses only have the same energy pool and that means that if you don't give them sunlight
19:41enough they'll kind of have to prioritize what they spend that energy on and that is why we want to
19:48make sure that our new roses have enough sun right and it is also important with healthy soil good air
19:57flow
19:57in the soil a thriving microbiome because there are microbiomes in the soil that can hurt your roses
20:06and the good microbiomes or the good bacteria and the good soil organisms protect against those
20:15so you do want a thriving soil also to avoid black spot and you want circulation because roses also need
20:23a
20:23kind of trade between oxygen and water right you can also spray your roses with all kinds of different stuff
20:32you can get stuff meant for it like here and you can also use a good old sulfur and you
20:40simply mix it into
20:41one of these sprayers here and you gently coat your roses you can always find the concentration on the back
20:47of your
20:48product so i'm not going to mention any but for most of you sulfur will probably be more than okay
20:54one
20:55thing i will mention though is you have to be a little bit aware of if you're breathing it in
21:01because
21:02a lot of these products are not that great for humans either if you catch my drift so but you
21:10can
21:10definitely get away with spraying the leaves of your roses the reason i sometimes don't do it is they can
21:16give a little bit of a miscoloring on the rose leaf and i don't always need it but if you
21:23have a problem
21:24child of a rose you can definitely do that but in general we want to be growing healthy rose varieties
21:31and that leads me to something else sometimes we have to get rid of a rose because the dna of
21:37the
21:38rose is simply unhealthy right it's like humans we don't always get the dna we want and the same with
21:44roses roses roses can sometimes be inherently unhealthy and then we have no choice but to get rid of those
21:52roses right but you can definitely spray your roses with sulfur or something else you buy commercially
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