Xtremehorticulture

Why Oleander Not Flowering

Q. I have a dozen, full-sized oleander plants I put in last year. I fertilized them with a 20 – 20 – 20 fertilizer. They are growing great but they rarely flower. Am I missing something or is it the fertilizer? Flowers of a full sized oleander shrub. Flowers grow on “current seasons wood”. In other words, the flowers form on stem growth this year, not last. A. It will probably take about three years for them to really start flowering a lot with that fertilizer and regular irrigation. Oleander loves irrigation water. It also loves fertilizer. The combination of regularly watering and applying a good fertilizer results in dark green leaves with lots of new succulent growth. This new growth is not yet fully mature. When it does flower a little bit later in its life, the show will be spectacular. Just be patient. If oleander is cut back hard, it will grow fast to reach close to its size before it was cut back. Some people call this its “root to shoot ratio”. When the plant has an existing large bunch of roots and the top is removed, the sbrub grows very rapidly until it gets back close to its original size. It doesn’t waste time and energy flowering yet. But it will when it gets larger.             The nitrogen in the fertilizer is the first 20. The second and third 20s stand for the phosphorus and potassium in the fertilizer. The middle 20, the phosphorus, encourages flowering but it also encourages the roots to get firmly established in the soil. Flowers will be produced on new growth. The more stems of new growth, the more flowers it produces. If the oleander is lush and bushy, it will be full of flowers and bloom when it’s ready. Dwarf oleanders stay small and flower at a smaller size than standard sized oleanders. When oleanders are young make sure there is plenty of phosphorus in the amended soil and then just feed it nitrogen fertilizer to get it big. This shrub will start flowering when it’s supposed to.

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Oleanders In Containers Not Blooming

Q. I have two pink dwarf oleanders planted in 18 inch clay pots which are healthy looking but very few blossoms. One of my “expert” friends says simply that “oleanders don’t like pots”. Another “expert” says that I’m watering too much. Are either of these guys right or do you have any suggestions that might get some some blossoms? Oleander flowers A. We have dwarf oleanders at the Research Center in containers and they bloom just fine. The usual reasons for a lack of flowering are not enough light and pruning them incorrectly. Oleanders use a lot of water when it’s present. There might be a couple of things you could try. Oleanders should be in full sun. They love the heat, and they love water and fertilizer to perform their best. If the container is smaller you might have to water more often. 18 inch containers are not that large and don’t contain a lot of soil. If the soil volume is not large, the plant may not have enough water in the soil to last between irrigations. Oleanders that are not getting enough water will look normal but have a very open canopy and not bloom well. Containers are not very forgiving when it comes to water. The water in that soil can be used up fairly quickly. You can try using a soil moisture meter that you can buy from the nursery for about $7 and check the soil moisture before you water. Water when the meter is about half way between wet and dry, do not let the soil go totally dry. Next, use a fertilizer like Miracle Gro or Peters and water it into the soil about once every six to eight weeks. Oleanders growing in the ground do not need to be fertilized as often. Next, cover the soil in the container with mulch to help keep the soil moist. About three inches would be enough. If oleanders are young or if they are pruned with a hedge shears they will not produce any flowers or very few. Don’t prune it with a hedge shears if you want flowers, contrary to how you see it done around town. 

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