Q&A for How to Grow Iris

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  • Question
    Do iris plants need full sun?
    Maggie Moran
    Home & Garden Specialist
    Maggie Moran is a Professional Gardener in Pennsylvania.
    Home & Garden Specialist
    Expert Answer
    Yes. Iris plants need a minimum of between 6-8 hours of direct sunlight each day.
  • Question
    When should you plant iris bulbs?
    Maggie Moran
    Home & Garden Specialist
    Maggie Moran is a Professional Gardener in Pennsylvania.
    Home & Garden Specialist
    Expert Answer
    It is best to plant iris bulbs in late summer or very early in the fall. This would be between July and September in the U.S.
  • Question
    How do you plant iris?
    Maggie Moran
    Home & Garden Specialist
    Maggie Moran is a Professional Gardener in Pennsylvania.
    Home & Garden Specialist
    Expert Answer
    Ensure it is in well-drained soil and has as a minimum of 6-8 hours of direct sunlight per day. An additive of Gypsum is a great way to improve the soil quality.
  • Question
    Do irises bloom the first year?
    Lauren Kurtz
    Professional Gardener
    Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.
    Professional Gardener
    Expert Answer
    It’s not uncommon for irises to skip blooming the first season after planting. In nutrient poor or dry soils the plants may use their first growing season to establish healthy roots and store energy. If irises don’t flower for a second year, some action may be required to get your iris back on track. If planted too deep and rhizomes aren’t showing on the soil surface, dig them up and plant them higher. They need at least 6 hours of full sun during the day so move to a better location if your iris location doesn’t meet this requirement. Over or under fertilizing can be a factor. Fertilize lightly with a fertilizer low in nitrogen.
  • Question
    Can old growth be cut back in spring?
    Lauren Kurtz
    Professional Gardener
    Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.
    Professional Gardener
    Expert Answer
    Yes. Cut back or completely remove brown and yellow leaves in the spring. Clear any debris from previous season away from rhizomes so they get better aeration.
  • Question
    Will the iris be harmed if I cut back the foliage after blooming is finished?
    wikiHow Staff Editor
    Staff Answer
    This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.
    wikiHow Staff Editor
    Staff Answer
    It is not recommended to cut the foliage after blooming has finished because the foliage is still doing the work of photosynthesizing to produce the energy needed for next year's new growth. It is best to do a tidying trim only at this time––cut away dead leaves and cut off brown tips only. You should also remove the flowering stalks, as this is important to prevent rot resulting from watering. Wait until next spring to do a full cutback of the foliage.
  • Question
    My irises haven't bloomed the last two years. What could be wrong?
    wikiHow Staff Editor
    Staff Answer
    This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.
    wikiHow Staff Editor
    Staff Answer
    There are several reasons why this can happen. One is that the plant is not receiving sufficient sunlight––check to see whether other plants have started to shade out the irises or if a new structure has been positioned that now creates shade over them. Another reason after a few years' growth is that the rhizomes have become too clumped together and need dividing to encourage new blooms; dig them up and replant the good ones and they should soon be blooming again.
  • Question
    How long do cut iris flowers last?
    wikiHow Staff Editor
    Staff Answer
    This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.
    wikiHow Staff Editor
    Staff Answer
    Cut iris flowers should last around 4 to 8 days when kept in a vase of water. Keep the flowers in a cool spot if you want to prolong the vase life but if you want unopened buds to open, you'll need to provide some warmth (just do not place in intense heat). Unopened buds with dry tips will not open. Keep the flowers away from ripe fruit or dying flowers, as the ethylene gas they emit will hasten the demise of the cut iris flowers.
  • Question
    How do irises grow?
    wikiHow Staff Editor
    Staff Answer
    This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.
    wikiHow Staff Editor
    Staff Answer
    Irises grow from fleshy roots, which are known properly as rhizomes. These rhizomes produce new rhizomes over the years, provided the irises are receiving the necessary nutrients and sunlight needed for good growth. In time, the rhizomes become quite clumped together and need dividing to encourage blooming. Irises can be grown from seed but this is for the advanced gardener, as it's a bit of challenge.
  • Question
    Are iris flowers scented?
    wikiHow Staff Editor
    Staff Answer
    This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.
    wikiHow Staff Editor
    Staff Answer
    Some irises have a scent, some are quite strong in fragrance. Other irises though, have no scent at all. If you're looking for scented irises, ask your nursery for their advice; to help you know what to look for, Iris pallida has a particularly strong scent, as do bearded irises.
  • Question
    What is the strange green bulb growth where the bloom used to be?
    Community Answer
    This is the flower producing seed. Cut the flower stems after they are finished blooming so your plant can put more energy back into the tuber instead of trying to produce seeds.
  • Question
    Can I transfer the iris in the spring?
    Community Answer
    Yes, this should work just fine.
  • Question
    Why have my irises' leaves flopped down?
    Pauline Donnelly
    Community Answer
    Assuming they are getting enough water, check for mold or borers. You have to check the bulbs.
  • Question
    Do irises change colors after a year or so?
    Community Answer
    They might change because of extreme temperature change, chemical drift, transplant issues or even a random rhizomes dug up by a dog can cause a stand of colour change.
  • Question
    When do irises flower?
    Pauline Donnelly
    Community Answer
    They flower in the spring. There are different varieties, so some flower earlier than others.
  • Question
    One of my Iris plants grew a bulb-looking thing where the flower was. I don't know what it is. Should I remove it?
    Community Answer
    It's a seed pod. If you want the seeds, leave it until it dries; if you don't want them, you can remove it,
  • Question
    When do I cut the dead flowers off?
    Community Answer
    When they start to die, and watering does not perk them up, cut the dead flower as close to the root as you can, taking care not to cut through the root as it will kill the other flowers.
  • Question
    After the plant has bloomed, what is the green-bulb like thing near the top of the plant?
    Community Answer
    The green bulb is a new plant growing on top of the old one. This bulb should be cut off and replanted, but only in July. If your new iris does not become a full-blown flower, your irises are broken, and you should discard them.
  • Question
    I have my plant in a pot and I live in South Texas. I'm afraid it will not survive our hot weather. We have winds during March so it dries the dirt around the plant. What should I do to help the plant survive the hot weather?
    Community Answer
    Cover the plant with a polythene covering and keep it in sunlight during the morning hours, then remove it. Evaporation will create water vapor that will give the plant continuous drops of water and keep it cool.
  • Question
    When is the best time to transfer and plant an already-established plant of iris?
    Community Answer
    Divide just about any time of the spring, summer or fall, as long as they can have a little shade and water to keep them hydrated. As they settle in, they do fine.
  • Question
    Why do the bulbs say to plant them in march?
    Community Answer
    That is around the time you should plant them for optimal growth and longevity. Irises will not grow all that well or stay around for all that long if you plant them in late summer. You do not necessarily have to plant them in March, just sometime around early springtime.
  • Question
    I planted 3 different irises this spring, and didn't expect them to bloom this year. To my surprise, one of them had buds! I expected it to open today, but when I checked the bud had fallen off. Why?
    Community Answer
    Most likely, your irises are broken, and you should discard them. Normally, irises should be planted in July -- early planting could be the cause.
  • Question
    Are irises a good cut flower?
    Community Answer
    Irises mixed in with other flowers, such as roses, make a beautiful bouquet.
  • Question
    Could I plant a rhizome that has no roots or leaves and expect it to grow?
    Community Answer
    Yes. Rhizomes are capable of sprouting and growing.
  • Question
    How do I get rid of aphids on my irises?
    Pauline Donnelly
    Community Answer
    I find soapy water to be helpful for aphids. It is relatively non-toxic. I don't really measure - just fill a spray bottle with about 1-3 parts dish soap and 7-9 parts water.
  • Question
    Do irises require mulch?
    Community Answer
    Lightly mulch if you have dry conditions, put down a thin layer of about an inch. Don't over-water, touch the soil with your finger for dampness, and make sure your plants are getting air circulation. Tip: Don't use mulch with dyes or paint.
  • Question
    How can I keep rhizomes alive in a pot throughout the winter while the plant is outside?
    Community Answer
    You can let the plants die back in a cold frame or cool cellar, but don't leave them out in sub-zero weather, since they don't have the soil around them for protection.
  • Question
    Can I cut the green off at fall?
    Community Answer
    As much as it pains you to watch the leaves turn yellow, brown and then get brittle as they die back, you need to leave them alone. The leaves left over after the flowers are what recharges the rhizomes below ground. If you cut the leaves off when they are still green, you rob the plant of energy that will be stored for next year's blooms, and eventually the plants will dwindle and die off.
  • Question
    My friend when trimming my irises back in the fall, removed one of the bulbs in the garden. Will my irises grow back next spring?
    Community Answer
    Probably only if the seeds are still there. You will also need to move the seeds in the house for awhile and put it by a window and water it.
  • Question
    What time of the year should I plant rhizomes?
    Community Answer
    March to April, but not late spring. I would recommend April. If planted near summer, the plants may dry up.
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