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 when planting  Knockout roses and they should reward you with disease free growth and prolific blooms.

Planting Knockout Roses - do this before planting

Make sure you plant your Knockout roses in a position that gets at least 5-6 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; all roses, including Knockout roses like a soil pH of about 6.5. There are simple to use pH testing kits available from your local nursery or garden centre stores.

Check the drainange – I can’t stress this enough – bad drainage is one of the main reasons newly planted roses can droop and die (other reasons they can droop and eventually die are not watering enough;  applying fertilizer to newly planted roses, esp bare-root roses; and overdoing the fertilizer when it’s time to fertilize (usually a month or so after planting).

So make sure the soil drains freely after a good soaking. Like any roses, Knock Out Roses hate wet feet. Rose roots left in waterlogged soil end up rotting. The fine root hairs that carry water to the rose plant rot and disintegrate, so even though the soil is wet, the roses roots can’t uptake that water to the rest of the plant. 

After making sure the soil drains freely, 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.

When planting bare-root knock out roses it’s a good idea to soak them for an hour before planting in a bucket of water that’s got some liquid seaweed mixed in at half strength (make sure it’s only at half the recommended dosage rate). While they’re soaking, dig out a hole large enough for the roots to spread across and deep enough for the bud union to sit just above soil level if planting in warm climate zones or just under soil level if planting in cold zones that have harsh winters.

How To Plant Knock Out Roses

When you’re ready to plant the bare root Knock Out 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 you’re planting a potted knockout 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. Again though, if you live in a cold climate zone where it’s recommended to plant your roses with the bud union just under the soil surface, then make the planting hole a little deeper (say 3-5 inches) for the potted rose so the bud union sits just under soil level.

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 Seaweedat half the recommended dilution rate and water that in. Liquid seaweed will help your knockout rose cope with the shock of being placed in a new environment and get it off to a good start. I never plant anything without doing this, but it’s important to water the plant in well first with just plain water, then use the half strength liquid seaweed.

I can’t stress how important it is to keep the water up to your newly planted roses for the first few months while they are establishing. Older, established roses can tolerate dry spells, but a newly planted rose needs plenty of water while it is establishing. If in doubt about whether it needs watering, stick your finger into the soil to check the first few inches. If it’s dry an inch or more down, it’s time to water.

And give it a long deep soak, not a quick spray. Long deep soaking helps the roots to grow deep. Shallow watering causes roots to grow close to the surface and in hot weather, esp if not mulched, the roses are more prone to moisture stress.

After watering your knockout rose in,  you can cover the soil with some mulch. Spread it about 2 inches thick to help retain moisture in the soil, and suppress weeds. Be sure not to put the mulch too close to the stem.

If the weather is still cool where you’re planting, don’t worry about putting the mulch around your rose until it gets warmer, so the soil has a chance to warm up. If you plant your knockout rose when the weather is quite hot, then put the mulch over the soil to keep moisture in, weeds out and the soil temperature cooler in the heat.

Please don’t fertilize your newly planted knock out roses until a month after planting, especially bare-root roses. The fine feeder roots are trying to establish and if you fertilize the roses, it will cause the tiny hairs on the newly forming feeder roots to burn and die and then there will be nothing to uptake water and nutrients to your plant.

This is the typical scenario of fertilizing at planting time or over-fertlizing when it’s time to fertilize; the plant droops or wilts after a short period of time because it can’t uptake the soil water because feeder hairs on the roots have burned, folks keep watering and feeding the rose wondering why the plant is still continuing to droop and not perk up, and its because there’s no root hairs on the roots to uptake the water and nutrients in the soil water, so the rose is just sitting there slowly dying from lack of water and nutrients even though there’s plenty of both in the soil.

That’s why it’s important to wait until the new buds have formed into shoots and the leaves on those shoots are leafing out to full size before you fertilize.

These steps on planting knockout roses should get them off to a flying start, and keep them growing vigourously and disease free for years to come.

48 Comments so far

  1. Hank Jones on July 5th, 2010

    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.

  2. admin on July 6th, 2010

    @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.

  3. Jim Bucknall on February 16th, 2011

    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.

  4. admin on February 16th, 2011

    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.

  5. Lori R on May 9th, 2011

    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.

  6. admin on May 14th, 2011

    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

  7. Leigh on May 15th, 2011

    I have been told that knockout roses should always be planted in groups of 3…..is this correct and why?

    Thanks

  8. admin on May 15th, 2011

    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.

  9. Pam on May 16th, 2011

    How far apart do you plant multiple roses if you are aiming for a hedgerow type border between two properties?

  10. admin on May 20th, 2011

    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.

  11. Nancy on May 22nd, 2011

    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.

  12. admin on May 22nd, 2011

    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.

  13. Chelsea on May 22nd, 2011

    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.

  14. admin on May 24th, 2011

    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.

  15. James on June 9th, 2011

    Can you please tell me how often to fertilize the roses and what kind do you recomend

  16. admin on June 9th, 2011

    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.

  17. Sue on June 16th, 2011

    When is the best time to plant rose trees?

  18. admin on June 17th, 2011

    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.

  19. Lori on June 18th, 2011

    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.

  20. admin on June 19th, 2011

    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.

  21. Jan on June 26th, 2011

    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?

  22. Jan on June 26th, 2011

    Meant to add that I’ll move the hydrangeas to a new location ;)

  23. admin on June 27th, 2011

    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.

  24. Patty on August 21st, 2011

    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.

  25. admin on August 21st, 2011

    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.

  26. Cindy on September 11th, 2011

    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?

  27. Cheryl on September 26th, 2011

    I bought a knockout rosebush the end of September and wondered if I should fertilize it when I plant it.

  28. admin on September 29th, 2011

    Hi Cindy
    I personally wouldn’t use a gravel mulch around roses. I give the reasons why here

  29. admin on October 5th, 2011

    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 4-6 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.

  30. John on February 28th, 2012

    Hi,
    I am going to buy barerooted
    knockout roses soon,( March 1st).
    Can I keep them in a bucket of water till end
    of last frost, about end of (April) and then plant them or must they be planted immeadiatly.
    Thank You

  31. admin on February 29th, 2012

    Hi John
    when you buy bare-root roses, you want to get them in the ground as soon as possible. There’s no way you can keep them for a couple of months before planting them out; the roots will have dried out and you’ll have dead rose bushes on your hands. I’d hold off as long as possible before getting the bare-root roses if you want to plant them after the last frost. I’m gathering you live in a cold climate zone, can you place the order with your nursery and ask them to hold off as long as possible on the delivery?

    Last year I bought some bare-root knock out roses by mail order later in the season; they were probably the last lot to be dug up and sent out, so why not phone a few reputable mail order rose nurseries and see if they can accomodate your request. Failing that, wait at least til the ground has thawed and the soil is workable before getting your bare-root knock out roses, and when you plant them if there’s still a chance of late frosts, cover the canes completely with some type of mulch to protect them.

    Also you only place the bare-root knock out roses in a bucket of water with some liquid seaweed at half strength an hour or so before planting them.

  32. katie on March 12th, 2012

    I live in TX and was going to buy some two year old bare-root knock out roses. Will they bloom this summer?

  33. admin on March 12th, 2012

    They certainly will Katie

  34. Linda on March 23rd, 2012

    We are planning to plant knockout roses along a split rail fence in an area that gets a lot of sun. I have read all of your tips here for planing etc., and wonder if you might address cutting blooms and pruning the bushes. Thank you.

  35. admin on March 23rd, 2012

    Hi Linda
    I have written an article about deadheading and pruning here.

  36. Gabe on March 24th, 2012

    This is my first plant I’ve planted on my own. My estfriend swears by them and after reading ur article my question is, if my stem is showing but mulch reaches it and covers the entire base is this a problem? Ad one more question, I bought them a few days back, their drooping a bit. I don’t want them to die. Anything Ivan do besides water them? I already placed them with mirical grow. Their in plenty of sun.

  37. admin on March 25th, 2012

    Hi Gabe
    your friend is right. Knockout roses are a great rose for a beginner to grow.

    I’m not sure what you mean by “stem is showing” as the stems are supposed to be showing. If you are referring to the bud union (that gnarly looking woody mass that the stems grow out from if the rose is grafted) that is OK to be showing; if you live in a warm climate you can plant your rose with that part of the rose sitting just above soil level. If you are in a cold USDA climate where it freezes through winter, you should plant it so that the bud union is just under the soil surface so that part of the plant is protected and can keep producing new stems come spring. Also with the mulch, just simply move it about 4 inches away from the stem.

    If your plants are drooping, make sure the water is draining away from the roots properly. Stick your finger in the soil around it to check that it’s moist but not still “wet” a few hours after watering.. Also make sure the water is reaching deep into the soil, not just the first couple of inches at the top. It’s important to give your knock out roses plenty of water when you first plant them (assuming the water drains away properly), so again check the soil to make sure the water is penetrating deep enough to the roots.

    Don’t use any fertilizer on your newly planted roses, especially if bare-root, until new shoots have leafed out and are actively growing; wait at least a month after planting before fertilizing. The only thing I put on newly planted roses is liquid seaweed at half the recommended strength.

  38. Kim on April 15th, 2012

    I have two knockout rose bushes. They are growing much slower than my mothers and the leaves are red. Could you tell me why they are red and what I can do. Thanks

  39. admin on April 15th, 2012

    Hi Kim
    The young developing leaves of new growth on knock out roses tend to be red until they mature and green out.

    Re their slow growth, you can’t really compare knock out roses growing in different places as there are too many variables; climate, aspect, the micro climates that can develop from one garden to the next, the soil they’re growing in, the maintenance they get, the particular fertilizer they get, the watering they get, the pruning height they were last pruned to, even the plants themselves. All of these conditions factor into their growth rate.

    Try giving them some liquid seaweed to help with root development which in turn helps above ground development.

  40. MELBA STANFORD on April 20th, 2012

    I purchased two knockout rosws,barerooted in Feb.2012. I planted them in late Feb. They are alreay blooming. I put them along a fence row on the west side. They get sun all day and plenty of air around them. The leaves stay green the year round. lovely in any seasson. Commercially the are used a lot in landscaping in this area of Texas.

  41. Jo on April 24th, 2012

    I would like to plant some knockout roses as a hedge along my fence line, in part to keep the grass from looking messy and growing up the fence. Can I just plant into the grass or would this make a bigger mess.

  42. admin on April 24th, 2012

    Hi Jo
    You would be better off making a garden bed to grow the knockout roses in. That way there’s nothing else competing with them for nutrients and water. The bed needs to be at least three feet in width as knockout roses grow 3-4 feet wide.

  43. Barbara thomas on May 25th, 2012

    I planted knock out roses 6wks ago they are alive ang geting blooms once in a while but they are not getting any taller.what am I doing wrong.They are the same height since I bought them thank you Barbara thomas in Texas

  44. admin on May 25th, 2012

    Hi Barbara
    It’s only been 6 weeks since you planted them; they are still getting established in their new spot. Just keep watering them regularly and feed every 6 weeks during spring, summer and early autumn and they will grow.

  45. Joyce Shannon on June 8th, 2012

    Can I put cedar mulch around my rose bushes I have a very large bed and weeding would be a lot easier

  46. admin on June 8th, 2012

    Hi Joyce
    Putting a mulch on your rose bed is a necessity if you want to prevent weeds from germinating, as well as keep the soil temperature even and prevent moisture loss from the soil during summer.

    I prefer to use lucerne hay or sugar cane mulch as a mulch around roses, as these decompose over a few months adding helpful organic matter into the soil, however they do need topping up every 6 months whereas wood bark mulch is slower to break down depending on the size of the wood chips.

    You should be fine to use cedar mulch. Just be aware that any kind of wood chip mulch can cause some nitrogen draw-down (soil microbes use up some of the nitrogen in the soil as they break down the wood chips). This shouldn’t be a problem if the soil around your roses gets fertilizer added to it regularly over the growing season.

  47. Georgia on June 22nd, 2012

    I’m planting 6 knockouts beside a garage that gets full sun, how far out from garage do I need to plant them? The bed is currently 3ftwith deep.

  48. admin on June 23rd, 2012

    Hi Georgia
    I’d plant them a 1 1/2 to 2 feet out from your garage.

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