Hello, Steve. I am assuming that what you purchased is a Hydrangea Macrophylla (a.k.a. a Mophead Hydrangea or a French Hydrangea) although there is also a chance that you may have a Macrophylla called Lacecap Hydrangea. Hydrangeas in general can be planted at any time. But it is easier to do so once the threat of freezes has passed in the
spring.
I lost a named variety here in Texas when I planted it June and had to leave for a week. Not even the automatic drip irrigation saved it. But I planted another one this year and it is doing well because I check it often. The problem with planting in the summer is that the
plant needs very frequent watering and, in your case, has little time to develop a root system that can withstand your
zone 5 winters. When that happens, you just have to baby it a lot in the summer and protect it like crazy during the winter.
By the way, if by "store bought" you mean that you bought the hydrangea at a grocery store or florist (in a pot with fancy aluminum foil), you need to be even more careful because some of those are not hardy.
Florist hydrangeas, as they are commonly referred to, are bred to grow quickly, bloom quickly and do so at "incorrect times" so they can be in stores by Easter and/or Mother's Day. They are also grown in temperature/humidity controlled
greenhouses and they are never exposed to
zone 5 wintry temperatures so not all develop the hardiness necessary to survive cold winters. But while they are notorious for being difficult to grow outside, it has been done before successfully. Winter is going to be your biggest hurdle.
Macrophyllas are best grown in
zone 8. Named macrophyllas (those purchased from local nurseries) can be planted in the ground as far north as
zone 5-ish as long as proper winter protection methods are followed. These methods aim to protect not just the
plant stems but the
flower buds that grow at the end of the stems.
Containers are an alternative that some people use to get around this issue. It requires that the
plant be overwintered in the coldest room in the house. That is because hydrangeas do best when they can have a period of domancy, brought on by freezing weather. Which is why you see them for sale in warm
zones like mine but not in warmer ones like Florida's
zone 10 and Hawaii's lower elevations.
If you decide to
plant them outside, consider the things previously mentioned by the others as well as:
1. All hydrangeas will bloom and grow well in morning sun and afternoon shade, specially the Macrophyllas. But if you live in the northern half of the country, you get a bonus: your hydrangea will tolerate
growing in even sunnier conditions! Full Sun in some cases. But if you have a florist hydrangea, let it get 3-4 hours of morning sun, approx.....
2. Most hydrangeas are pot-bound when purchased. The roots have so filled the pot that they circle the pot. As a result, the
plant dries out and wilts much quicker than you expect. If you notice this on your
plant, cut the roots every 2 inches and with your fingers force the roots downwards. Dunk the whole thing in Liquid Seaweed/Water (or rooting hormone solution with water) and then place it in the planting hole. Your soil should drain well; ammend it with organic compost if necessary.
3. It takes hydrangeas about a year to become established. That means that they can handle the summer and winter months. So, this summer, it is essential that you keep the soil under/around them moist (not wet), as Bill stated.
If you go overboard with watering, they can develop root rot so be careful. Add 2-3 inches of mulch, water in the mornings only and make sure you do not water the leaves in order to prevent fungal infections.
Wilting is a condition that you may see often this time of the year. And specially on hydrangeas planted any time this year. It occurs when the the
plant looses water thru the leaves faster than it takes water thru the roots. Hot temperatures and / or windy conditions will cause wilting. That is the nature of the beast when one purchases
plants with big leaves.
It is ok to see wilting during the summer as long as the
plant has recovered by next morning. Because your soil type (sandy, loam, clay, etc)may be different than mine, plan on watering about 1 gallon of water every 2-3 days during the summer.Increase that if the
plant remains wilted in the morning for several days in a row. Decrease the amount of water in the Fall. Make sure that watering wets the root ball.
Last watering suggestion: water them the day before a freeze.
3. Hydrangeas are not heavy feeders. This year, give the
plant some Liquid Seaweed/Water Solution and that is it. Starting next year, apply 1 cup max of manure or cottonseed meal in early June and that is it. Spread them in the soil thr u the drip line.
4. Any
flowers that you see this year formed from
flower buds that the hydrangea grew last year (during the months of August-October). You want to baby the
plants specially well between the time that buds form and the time that the
plant blooms.
5. Macrophyllas usually do not need pruning. I recommend you do not prune yours this year at all. Next year, if you have to prune then prune 2-3 weeks after flowering.
flower buds develop between August-October so, pruning after August comes at the expense of blooms next year.
Good luck with your new
plant and feel free to stop by again if you have any questions/problems!
Luis
