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Hydrangea and rhododendron feed

Pam100Pam100 Posts: 85
Hi everyone. I’ve just pruned my 2 hydrangeas. They look healthy and have always flowered well. I was wondering if hydrangeas and rhododendrons should be given a feed in the spring and if so, what would you recommend. Thanks 

Posts

  • PurpleRosePurpleRose Posts: 538
    These are acid loving plants so they would benefit from an Ericaceous Feed. I normally give them a feed of this approximately every 2 weeks while they are growing
  • Pam100Pam100 Posts: 85
    Thanks PurpleRose
  • luis_prluis_pr Posts: 123
    edited March 2021
    I usually wait to start feeding them until after my average date of last frost for my area. Just because I do not want to encourage lots of growth and then winter returns. While the late frost will not usually kill a hydrangea and may not always kill the stems and the invisible flower buds, they can zap the foliage and the plant looks uuuuugly for 2-4 weeks until new foliage develops.

    Since hydrangeas/rhosides are not fertilizer "hungry" plants like roses are, I fertilize them only for a few years, until they are established in my garden. My fertilizer selections for Spring use only: either cottonseed meal, organic compost, composted manure or a general purpose, slow-release chemical fertilizer with a NPK Ratio of around 10-10-10. If the plants are potted, I use a fertilizer for azaleas/camellias/hydrangeas/blueberries that also includes secondary nutrients and apply it per the label directions (very little or none at all during winter). After the plants are established, I just maintain them well mulched all year and they will feed off the decomposing mulch. However, if your soil has nutrient deficiencies (like with sandy soil), you may want to feed them every 3 months.

    In some years, I may also give them some liquid seaweed, liquid fish or coffee grounds during the growing season. These are "weak" fertilizers... with small amounts of nitrogen and lots of secondary nutrients. I try to do my last fertilizer application about three months prior to my average date of first frost.

    With varieties that are evergreen or in areas with no chance of cold weather, I have used in the Fall/Winter fertilizers whose nitrogen content is either zero or close to that (like 0-10-10). But that was in the tropics or close.


  • ButtercupdaysButtercupdays Posts: 4,536
    Hydrangeas do not need acid soil to grow, and for white flowered varieties it does not matter, but if yours is a variety that has blue flowers you will need to plant it in acid soil or ericaceous compost to keep it that way. In alkaline soil the flowers turn pink.  You may be fine with that, but if not you can buy hydrangea colourant, or feed containing sequestrated iron to get the coloup you want.
    My garden soil is naturally acid and I have one that is a lovely blue, but being contrary that wasn't good enough for me, so I planted a dark pink one where it gets all the run-off from my limestone chipping drive. Success :)

  • luis_prluis_pr Posts: 123
    edited March 2021
    Just be careful with the acidity (or lack thereof) though. They tolerate alkaline soils but only to a point. You can use a soil pH test kit or visually monitor the foliage. The leaves should be dark green but, when the soil pH goes above 7.0 (neutral), the leaves will only tolerate it for a while. My soil pH is 7.6 which produces pink blooms and causes iron chlorosis in the leaves so I have to amend the soil once or twice a year.

    If the soil pH gets too alkaline, the roots will be unable to absorb some nutrients and you will notice dark green leaves turning a lighter green color at first. Then they turn yellow, except for the leaf veins which remain dark green. If the nutrient deficiency gets worse, the leaves turn white except for the veins. Finally, the leaves brown out and die. Blue hydrangeas will shift to purple and then to a shade of pink as the soil pH changes from acidic to neural to alkaline but the actual changes and speed of changes vary based on the hydrangea variety. For example, the color purple occurs on some cultivars more easily as the soil pH approaches 6 to 6.5 but only within a rather narrow band of soil pH. These plants -usually sold with names containing the word "purple"- actually resist turning blue. In general, as the soil approaches neutral (7.0), blue blooms will shift to a shade of pink but some plants will actually get rather light blue or light pink or even a light green.

    I have an unnamed reblooming lacepcap that was purchased without blooms and it had the label of mophead Nikko Blue. Oh well. I has pink lacecap blooms and, for the last decade or so, I have experimented with it by adding larger amounts of acidifying amendments to turn the blooms blue. Well, in the course of making these changes gradually, the blooms turned a series of very light purples or maybe lavenders that I preferred so, I now maintain the current level of pH to continue this lavender/purple-ish color instead.

    Feel free to "play" with these colors as you wish. Just do not apply too "too much" suddenly because hydrangea roots are tiny and shallow so they may be sensitive and be damaged by large amounts of these sulfur-containing amendments.
  • Pam100Pam100 Posts: 85
    Thanks for all the advice. I have acid soil so I will just give them a good mulch and watch them bloom 😁
  • luis_prluis_pr Posts: 123
    Post bloom pictures here too if you can! :)
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