A tale of 2 plants: An oakleaf hydrangea experiment

To make an immediate garden statement, think bigger when it comes to buying perennial shrubs

In July 2018, two oakleaf hydrangeas arrived at my door. They were the same variety, Proven Winners 'Gatsby Moon', but in two different sizes: a quart and a gallon. 

July 2018.

Photo from Proven Winners.

When it comes to buying shrubs, you need to ask yourself what you want for your garden. Are you willing to wait for a plant to reach its full size, or do you want the garden to look more established faster?

To be honest, I've always been a bit of a "go big or go home" type of gal. My shopping habits have often veered me to the larger shrubs, planters, hanging baskets ... you get my drift.

Bigger plants usually come with a larger price tag, but I see that as a trade off for the amount of time that has already gone into growing the plant. (For example, I don't have 10 years to wait for tiny arborvitae shrubs to grow in to block the street view — so I would buy larger plants.)

So if you purchase a smaller version of a shrub to save money, you'll need to be willing to wait a bit longer for that shrub to reach its full size.

But if you get the larger variety — which is often a more mature plant — you will be closer to filling the empty spot in your garden because the plant is already on its way to reaching its full-grown size.

Which brings me to "the experiment." Same plant variety, but two different sizes. How fast do they grow in the garden?

Quart vs. Gallon

To make this fair, I planted both plants in the same area of my front garden, where they receive roughly six hours of sunlight a day. I planted them about 48 inches away from each other. I also tried to give the plants the same amount of water (outside of rainfall) so if I watered one on a hot day, I watered the other as well. (I did water more the first year to help them get established in the garden. This year, I let them rely primarily on rainfall.)

The larger 'Gatsby Moon' in the front garden in August 2018.

The smaller 'Gatsby Moon' in the front garden in August 2018.

For the first few months after planting, the hydrangeas grew just a little bit. During this time, the growth was happening below the soil line — getting the plant established and building roots. A warm fall helped the plants get settled in for the coming winter.

The larger 'Gatsby Moon' in mid-October 2018.

The smaller 'Gatsby Moon' in mid-October 2018.

The shrubs made it through the winter without any issues. As spring progressed, the plants continued to grow.

In May 2019, the larger 'Gatsby Moon' (left) and the smaller 'Gatsby Moon' (right).

First year findings

I was surprised by how much taller the smaller version grew in its second season (spring and summer 2019). The shrub, in May 2019, was very small (see photo, above right). As of today, the shrub has two large stems — one measuring 36 inches and the other 24.5 inches. The plant measured 38 inches wide. That's a crazy amount of growth in one year, which I wasn't expecting!

Not surprisingly, the larger variety continued to grow well, but the growth focused on expanding its width more than height. The plant expanded to 46.5 inches wide and 42 inches tall.

The larger 'Gatsby Moon' measures 42 inches high after its first year of growth (August 2019).

The smaller 'Gatsby Moon' has one stem that is 36 inches high (August 2019). 

While the shrubs did not bloom this year (the plants bloom on old wood), I'm looking forward to seeing how the larger plants pair with the neighboring witch hazel for autumn color. I will continue to monitor the growth of the shrubs in the garden to see when the plants even out in size.

Thank you to Proven Winners for supplying me with two sample oakleaf hydrangea varieties to test in my Zone 6b garden.