We are in a drought, and we can see its effect on lawns that are not irrigated. They are brown and about the only things that are green and growing are crabgrass and some of the clovers. At least these dry lawns do not need to be mowed very often.

Since the growing season usually begins in April, we will look at the rainfall since April 1. According to the Weather Underground website, we have received only 6.66 inches of rain since then (as of August 10), while in an average year we would get 15.26 inches of rain.

The rainfall was not evenly distributed, however. In April and May we got 1.48 inches of rain while we normally get 7.63 inches. June looks more normal, at 3.21 inches. We usually expect to get 3.43 inches. But the June data is deceiving, as we got about half of that rainfall (1.63 inches) on two consecutive Sundays (June 21 and June 28). I was driving during those rains, and at one point it was coming down so hard that I had to pull off to the side of the road. I could not see the road because my windshield wipers could not keep up with the rain. And on July 1 we received 1.09 inches of rain, which is 60 per cent of the total rain we got in July.

It did not rain on 99 of the 132 days since April 1. On 15 of the 33 days it rained, we got 0.05 inches of rain or less. That amount of rain is about enough to get pavement and vegetation wet, but it provides little moisture to the plant.

So we are in a drought. So what?

This lack of rain means that plants do not grow as much. There are a lot of meadows around that are being invaded by trees. Some of these meadows are mowed annually, generally in the late fall to keep the oaks from getting so tall that they cannot be mowed with a conventional tractor. This year, the invading oaks in those mowed meadows are only one to three feet tall, and are generally shorter than the little bluestem grass and the wild indigo. In contrast, these same oaks with normal rainfall will range from five to eight feet tall. Their short stature this year is due to the drought.

Their short stature and smaller area of leaf coverage means that there is more ground space for grasses and wildflowers, plants that are usually shaded out by the taller oaks. Many people have commented that the orange-flowered butterfly weed is more abundant and more spectacular than in past years. And the yellow blooms of wild indigo were so pronounced this summer that Suzan Bellincampi wrote about them in this column on July 23. Is this due to the drought and the smaller oaks?

Another native grassland species, sandplain blue-eyed grass, was particularly abundant on one Chilmark property in 2007. Wendy Culbert and I documented more than 200 individual plants of this rare species. The following year, which was much wetter, this species was much less common, while its close relative, eastern blue-eyed grass, was more abundant. Moisture matters.

Droughts can also affect the survival of large oaks, especially oaks that are stressed by other forms of disturbance. The combination of a drought in 2007, (after three consecutive years of droughts) with complete defoliation, primarily by the fall cankerworm caterpillar, resulted in 500 acres of dead oak trees on the Francis Newhall Woods Nature and Wildlife Preserve and the adjacent Polly Hill Arboretum. As an aside, the cycle of defoliation may be starting all over again. The oaks in my neighborhood were completely defoliated this spring, and there are scattered dead trees as a result.

If there can be any such thing as a general statement about nature, it is that native plants are better at surviving droughts than introduced plants. Native species are adapted to the variability in our climate, while introduced species are not. This is an important idea if one of the goals for landscaping your yard is to reduce the amount of maintenance needed to keep your yard looking nice. The necessity of watering your yard will be reduced when native plants are used. And there is an ever-increasing variety of attractive native plants to aid you in such a worthwhile endeavor.

Robert Culbert leads Saturday morning guided birding tours and is an ecological consultant living in Vineyard Haven.