A very frequent question on the Message Board and in my email box concerns plants that are not blooming, or bloomed at one time and are not blooming now.
Here are some of items of consider.
Most H. varieties will withstand local sub-freezing temps in most areas especially if they are native to that area. Adding fresh mulch 2-4 inches high from the fall leaves is an excellent protection.
Problems arise from late freezes in your local area after the new buds begin to set. Keep a close on on your H. toward the end of the winter. If a freeze is forecasted and your buds are set, then covering for that night or two may be warranted.
To check if you buds have been frozen, break one or two in your fingertips. If there is no green color, they have probably been frozen.
Many plants are forced to bloom at the wholesale nursery to make them look good. There is too much foilage than the root system can support long term. I find this especially in one gallon pots. Blooms are there for the sale, but seem to fail quickly. Enjoy the blooms for a days or so, but cut them off to let the plant grow. There will be plenty of time for blooms in future years.
If the plant still looks stressed, try cutting back the foiliage, a couple of stems at a time, or try trimming all of it from the ends by 2-3 inches, kind of your choice. If it doesn't work try some more. When I got my PG a couple of years ago, I immediately took out 25-35% of the branches and used the cuttings to pot for new plants. The plant survived and is doing very well.
For many, but not all varieities of H., buds form on last years stems. The new stems in the current year produce no blooms - or at best only a few poorly shaped blooms toward the end of the season. See the Pruning Page. Remember certain varieties such as Annabelles will die back to the ground each year. That is perfectly normal. You need to check out the specific H. variety you have.
NOT ENOUGH SUN
How much sun is always a tough question. In "dog days" of July and August here in the south (Zone 7 - North Central Alabama), the afternoon sun and 90 degree plus temperatures often cause my H. to wilt. There is really little danger, as long as the plants recover at night. Continous wilting is a sign that more watering is needed.
As a rule of thumb, I usually say 4-6 hours of sun is good for typical H. Heavy partial shade and full shade all day will definately reduce the number and size of the blooms.
Thanks to Randy for the following additional suggestion.
"I hope you will also include the (Bloom booster) High Phosphate, high middle number Fertilizer, some like 10-52-10. It has worked wonders for me over the years and I apply it to any/all plants that fruit or flower. Will look forward to page on the subject. You are right, there are these questions over and over. Best wishes. Randy"
Unfortunatly, there are different opinions on fertilzing. Here's is the information on fertilizing from the Hydrangeas Plus website.
"If your hydrangea’s leaves are lush and green but don't have any blooms, it could be that you're fertilizing too much. Hydrangeas bloom best if they are a little stressed. High nitrogen-based fertilizers can actually inhibit blooms on most varieties. Hydrangeas don’t like to be overfed with fertilizers. Some hydrangea growers never feed their hydrangeas and have great blooms and healthy leaves. However, some must feed every few months to maintain the healthy plant. It really depends on your soil and the nutrients that are found naturally in your soil. Luckily, hydrangeas are such wonderful plants, they will tell you what they need.
As a general rule, we recommend fertilizing twice: early spring and early fall. Use a time-released fertilizer that releases slowly (by water or temperature or both) over a 4 to 6 month period. A commonly available product is called Osmocote but there are other brands that are equal. The general blend that yields 10-10-10 or 16-16-16 is all you need. There is no need to run out and buy a special fertilizer for every variety of plant in the garden. This particular mix is great for everything.
There are some fertilizers just for acid loving plants available on the market. These are a great instant boost for plants but tend to be very high in nitrogen and may actually inhibit the ability for the plant to bloom. Too much nitrogen and the plant will focus on stems and roots – which is not a bad thing. However, you bought these plants to bloom so there needs to be a balance.
Our recommended use for these instant fertilizers is for emergencies only. In May or June (depending on your area) hydrangeas begin to set bud and grow very quickly. The hydrangea will begin absorbing nutrients from the soil at a very rapid pace. If your soil doesn’t have enough nutrients, hydrangeas may get yellowing leaves on the inside parts of the plant. This is a perfect time for the instant fertilizer when the hydrangea needs it most.
What do your hydrangeas need in terms of fertilizing? The three essential components of fertilizer are nitrogen, phosphorus and potassium, the N-P-K numbers on any fertilizer. Nitrogen is for healthy green growth by helping the plant to grow chlorophyll. Fertilizers high in nitrogen like 25-10-10, is great for greening up your lawn. Phosphorus helps a plant grow good roots and stems in the early growth season then in flower production. A mix like 10-30-10 is great for flowers on your annuals and perennials. The Potassium (K) helps your plants generate and process nutrients. Other important elements in fertilizers are calcium, magnesium, iron, copper, manganese, zinc, and sulfur. Organic fertilizers are usually very low in these trace elements.
Hydrangeas like a balanced fertilizer. We prefer the granular time-released kind that delivers nutrients to the plant constantly for a 3- or 4-month period. Water will break down the outside coating of the fertilizer slowly and nutrients won’t dwindle out in the active spring growth season. Be sure that the soil is slightly moist when applying the granulated variety and keep the fertilizer off the foliage to prevent burn.
For blue hydrangeas, a low phosphorus element (the ‘P’) is important as too much will limit the plant’s ability to absorb aluminum. The amounts of sulfur (lowers pH) and calcium (raises pH) are important to keep the blue color. A good soil test from your local garden center can tell you what elements are missing from your soil."
If you have anything to add here, please email me. Pete
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