Knock Out Roses – How To Plant Them
Knock Out roses are supposed to be one of the hardiest, and disease resistent roses available at the moment. In order to keep them disease resistent you want to plant them in an environment that’s conducive to their health and vigour. Follow these steps for planting your Knock Out roses and they should reward you with disease free growth and prolific blooms.
Pre Planting Preparation
Make sure you plant it in a position that gets at least 4-6 hours of sun each day. If they don’t get enough sun they start getting sparse foliage and become more prone to rose diseases.
Check the pH of the soil. Roses like a soil pH of between 6 and 7. There are simple to use pH testing kits available from your local nursery or hardware stores.
Check the drainange to make sure it drains freely after a good soaking. Like any roses, Knock Out Roses hate wet feet and become prone to disease and dieback in poorly drained soil.
Add some well composted and milled cow manure or rose planting compost to the soil. Avoid fresh manures or rose food at planting time so you don’t burn any newly forming fine root hairs.
Planting.
When planting bare-root knock out roses, dig out a hole large enough for the roots to spread across and deep enough for the bud union to sit about an inch above soil level if planting in warm climate zones or just under soil level if planting in cold zones that have harsh winters.
Before planting the bare root rose, make a small mound at the bottom of the hole and sit the rose on that and spread the roots out without any kinks in them. then its just a matter of backfilling the soil and firming it down well but gently as you go. You don’t want to compact the soil too tightly so there’s no tiny particles for soil air but you don’t want to backfill too loosely either and have too many air pockets around the rose roots.
If it’s a potted rose, just dig a hole double the width of the pot and at the same depth as the pot so that once planted, the rose sits at the same soil level it did whilst in the pot.
Remove the rose from the pot and gently tease out some of the fine feeder roots, then place in the hole and backfill as above.
Give the rose a good watering, then fill up a watering can and add liquid seaweed like Maxicrop Liquid Seaweed
After this you can cover the soil with some mulch like Element 6 Organic Mulch
These steps should get your Knock Out roses off to a flying start, and keep them growing vigourously and disease free for years to come. Click the following link for helpful information on pruning Knockout roses
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I am just learning about roses and have purchased two Knock-Out roses in pots. I was hoping to get to climb a trellis, but I have read that they grow only to about 4 feet high.
Is there anything I can do to get Knock-Out roses to climb ?
Thank you for any suggestions.
@Hank
Unfortunately there aren’t any climbing knock-out roses on the market as yet. You can’t get the shrub ones you bought to climb. Maybe the breeders will be able to hybridize them so that a climbing variety will be available one day. Wishing you success with the two new ones you just bought.
We have a small garden of about 8 roses which are not puting on growth.
Also this garden has a mass planting of violets which cover the entire area and right up to the base of the rose bushes.
Would it be better to remove the violets from around the base or indeed to remove the lot.
Hi Jim
If it was my rose garden I would remove the violets. As beautiful as it must look, the roses are competing with them for water, air and nutrients. It would basically be like planting the roses in lawn with the lawn coming right up to their bases. It robs the roses of all the essentials they need to grow robustly, plus the dense underground planting creates extra humidity around the rose plants which can encourage the development of fungal diseases like blackspot. Take care when removing the violets as you don’t want to disturb the feeder roots of the roses that sit close to the soil surface.
Don’t dig them out with a hand spade, rather grab around the base of each violet and gently tug it from side to side until the roots come away from the soil, leaving the soil reasonably intact. Unfortunately you won’t have much, if any, soil around the roots of the violets so if you plan to keep them, don’t do this in the heat of the day or in direct sun, and have some pots filled with soil next to you that you can pop them in straight away so their roots don’t dry out and water in well as you fill each pot with as many as you can fit in.
I would like to plant some knock out roses on the east side of my house. They would get direct sunlight from sunrise until about noon, then shade from then on. I live in the midwest where we have 4 distinct seasons, moist springs and hot/humid summers. I would like to know if they will grow well in this area. Thank you.
Hi Lori
The only problem I can see with you planting roses in that position is that you mention you get moist springs and humid summers and if roses are planted against the side of the house then there will be a lack of air circulation around them. If roses don’t have good air circulation around them then they are much more prone to getting fungal diseases like black spot especially seeing you live in what sounds like a fairly humid climate where good air circulation is essential
I have been told that knockout roses should always be planted in groups of 3…..is this correct and why?
Thanks
Hi Leigh
If you only had room to grow one knockout rose that would be fine. You can grow just one if you wanted to. The reason it’s said to grow them in 3′s is because roses, like most small shrubs when planted in 3′s, give a more concentrated burst of color when planted in a group together, so it’s only for aesthetic reasons, not for any other reason. It won’t make any difference at all to their health or vigor if they are grown singularly or in groups of 3 or more.
How far apart do you plant multiple roses if you are aiming for a hedgerow type border between two properties?
Hi Pam
it would depend on the width of the species of rose you plan to grow and how dense you want the hedge. As a rule of thumb, plant them at half the distance you normally would. So for example for a dense hedge if the rose grows three foot in width, plant it two foot apart so the last foot of width of one rose bush blends with the first foot in width of the next to form that hedged look. If you don’t want it so dense then plant 2 1/2 foot apart, so only the last 6 inches of each blends together. Also be sure the roses you use for the hedge have good disease resistance as closley planted roses lack air circulation which makes them more susceptible to fungal diseases.
I received a knockout rose for a gift and it has lost all of it’s buds and roses because I was unable to find a suitable location to plant it in my yard. I love the knock out roses and was wondering if I could plant it in a pot? I hope that it is not dead by being in the small pot it came in. The leaves are still green but if I do not water it almost daily it looks droopy. I do not want to lose it. Thank you for your assistance.
Hi Nancy
You should be able to grow a knockout rose successfully in a pot so long as it is big enough, say around 18inches or more across. Make sure there’s drainage holes in the base of the pot and in the heat of summer make sure you water it daily, as pots can dry out quickly in the heat. Normally you would feed roses in the ground every 6 weeks during the growing season, but when they are in pots, they need fertilizing more often because all the extra watering leaches the nutrients out of the pot. For roses that I grew in pots, I would fertilize them once a fortnight. I just used an all purpose fertilizer that could be mixed in a watering can with water and also added a little liquid seaweed to the mix (follow recommended mix rates on bottle) and watered that in. Always water the plants first, before fertilizing and always follow the mixing directions to the letter. Don’t mix more than is recommended. That’s one of the prime reasons roses in pots die. Folks think that adding a bit extra into the watering can will help the rose grow better when in actual fact the reverse is true. If you don’t want to muck around with watering cans, you can always use a slow release fertilizer specified for potted plants and follow the dosage rates on the pack.
I recently purchased 2 knockout rose plants and really don’t know where to put them. I have 2 small beds on each side of my front porch, one side gets full sun and the other gets afternoon shade. Could I put one rose plant in the middle of each bed or should I put both together on the full sun side? I really don’t know how big they get and the beds are only about 4 ft long, 2ft wide. I also bought 4 upright plants, two are a tall lilly and the other i’m not sure (tall purple flowers). I thought I would plant 2 of those on each side and then just use some ground cover. They’re all full sun plants so i’m rethinking whether to put any of them in the partial sun side. I just wanted both beds to match, but I did grab a plantain lilly and some partial sun ground cover for that side just in case. You can tell I do NOT have a green thumb so any advice would be great.
Hi Chelsea
If the bed that gets afternoon shade gets at least 5-6 hours of sunlight before it gets shaded, then the knock out rose should be OK to plant in that bed. Knock out roses can grow up to 3-4 feet high and as wide. It seems to get to its max height in the warmer zoned climates. If the beds are 4 foot wide, and your knock outs grow to say 3 foot in width, it doesn’t give you much room to plant the other upright plants. Check the width measurements given for them on the labels to see if they will fit. If they don’t grow too wide, you could probably put one of them next to the roses. If you still wanted to plant those other plants in the beds, you could always grow the knockout roses in large 18 inch pots. I usually don’t like planting ground covers under roses because it creates extra humidity around the rose plants which makes them more prone to disease, but knock out roses are pretty disease resistent and if you don’t live in a hot, humid climate, then the groundcovers could be planted. Just be sure that they don’t grow too close to the base of the rose plants.
Can you please tell me how often to fertilize the roses and what kind do you recomend
Hi James
you should fertilize your roses every 6 weeks during the growing season – mid spring through to late summer/early autumn. I recommend to alternate between organic and chemical fertilizers eg for the first spring feed, use some organic fertilizer on your roses, then at the next feed, use a chemical fertilizer recommended for roses, then the next go organic again. Ask at your local garden club what their recommendations are for the area you grow your roses.
When is the best time to plant rose trees?
Hi Sue
It depends on your climate.
In a warm climate zone: you can plant bare-root roses in winter/early spring and potted roses can be planted in spring, early summer and autumn. Don’t plant in the height of summer if your climate has very hot summers.
In a colder climate zone: you can plant bare root roses in spring after the last frosts. Potted roses can be planted in spring, summer (if temps don’t get too hot) and early autumn.
I planted knockout roses two weeks ago and all the flowers fell off. Is there anything I can do to bring them back? They are planted in a spot where they get plenty of sun.
Hi Lori
Once rose flowers have bloomed they will eventually fall off the rose bush. You will get more new blooms to replace those spent flowers. Check the soil moisture so it’s not too dry and water if necessary; also make sure drainage is good and water drains away – roses don’t like wet feet.
I would like to plant my double knockouts where I currently have hydrangeas that sulk in the hot afternoon sun. Can I put the knockouts in this same area? Will the soil affect the knockouts? Is afternoon sun ok for knockouts?
Meant to add that I’ll move the hydrangeas to a new location
Hi Jan
They should be fine in the afternoon sun, just keep the water up to them on those hot days and make sure the soil drains well. After you remove the hydrangeas, improve the soil with the addition of plenty of organic material like compost or composted cow manure. Never use fresh manures in the soil if you are going to be planting straight away, always use composted manures. After planting the roses, water them in and then make up some liquid seaweed in a watering can at half strength and water that in to get them off to a good start. Don’t add any fertilizer to them for 4 weeks to let new roots establish in their new position without “burning” (liquid seaweed is not a fertilizer so won’t “burn” your new roses). Then use a good quality rose fertilizer on them. Then feed every 6 weeks during their growing season with a good quality rose fertilizer.
I have 3 knockout rose bushes. The first year they were fine. This, the second year they have grown to 4 1/2 feet tall and 4 1/2 feet around. I cannot use anything this large where they are at. Is there any way to keep them smaller? Or can they be cut down and then put in an 18″ containner? If I decide to move them, and they be moved in the fall, or do I have to wait till spring? I live in the midwest, and have all the extremes of weather, 5 below in the winter 102 in the summer.
Hi Patty
If you would prefer not to move them you can keep them in their current position but just regularly cut them back to keep them to the height you want. Rose growers regularly deadhead their roses by removing the spent flowers and you could just do the same with these knockouts but just trim off a bit more than you would if you were deadheading them.. When they get to the size you prefer (eg 3 feet x 3 feet) let them grow another 6 inches and then cut them back by that 6 inches after they’ve had a flush of flowers. Then let them grow another 6 inches and have another flush of flowers, then trim back again to the height you prefer. It may require a bit more pruning through the growing season but at least you will have them staying at the height you prefer. Keep feeding them every 6 weeks through the growing season as well.
If this is too much trouble and you would prefer to move them into containers then wait until they go into dormancy (that’s usually winter in mild climates but check with a plant nursery or local garden club for the right time in your area) prune them to 12 – 18 inches in height and then move them.
I was thinking of planting a line of knock out roses along the edge of the woods on my property. I wanted to line the bed with white gravel instead of mulch. Do you see any problem with this?
I bought a knockout rosebush the end of September and wondered if I should fertilize it when I plant it.
Hi Cindy
I personally wouldn’t use a gravel mulch around roses. I give the reasons why here
Hi Cheryl
DO NOT FERTLISE your knockout rose when you plant it. You can add some bagged “composted” cow manure (not fresh) or compost to the soil before planting it but don’t fertilise your rose until it’s been in the ground at least 6 weeks and new growth is starting to shoot from it. Adding fertilisers or fresh manures at planting time will “burn” the newly forming hair-like feeder roots and could kill your rose.